complexation of substituted guanidines with transition...
TRANSCRIPT
Complexation of Substituted Guanidines with
Transition Metals and Their Biological
Screening
Islamabad
A dissertation submitted to the Department of Chemistry,
Quaid-i-Azam University, Islamabad, in partial fulfillment
of requirements for the degree of
Doctor of Philosophy
in
Inorganic/Analytical Chemistry
by
Muhammad Said
Department of Chemistry
Quaid-i-Azam University
Islamabad
2013
Complexation of Substituted Guanidines with
Transition Metals and Their Biological
Screening
Islamabad
by
Muhammad Said
Department of Chemistry
Quaid-i-Azam University
Islamabad
2013
Declaration
This is to certify that this dissertation entitled “Complexation of substituted guanidines
with transition metals and their biological screening” submitted by Mr. Muhammad
Said S/O Sher Ghani, is accepted in its present form by the Department of Chemistry,
Quaid-i-Azam University, Islamabad, Pakistan, as satisfying the partial requirements for
the award of degree of Doctor of Philosophy in Analytical /Inorganic Chemistry.
External Examiner (1): __________________________________
External Examiner (2): __________________________________
Head of Section: __________________________________
Prof. Dr. Saqib Ali (PoP)
Department of Chemistry
Quaid-i-Azam University
Islamabad.
Supervisor & Chairman: __________________________________
Prof. Dr. Amin Badshah (TI)
Department of Chemistry
Quaid-i-Azam University
Islamabad.
IN THE NAME OF ALLAH
THE COMPASSIONATE
THE MERCIFUL
Dedicated to
My Loving Parents &
Respected Teachers
Contents
Page
Acknowledgement i
List of Figures iii
List of Tables vi
Abstract vii
Chapter-1 Introduction 1-30
1.1 Introduction 1
1.2 Applications of guanidines 2
1.2.1 Naturally occurring guanidine compounds 2
1.2.2 Guanidine based pharmaceutical compounds 2
1.2.3 Paper and membranes with antibacterial activity 5
1.2.4 Catalyst for organic synthesis 6
1.2.5 Uses of guanidine salts 6
1.3 Synthetic strategies for substituted guanidines 6
1.3.1 Guanidine synthesis by guanylation reaction mechanism 7
1.3.1.1 Guanylation by thiourea 7
1.3.1.2 Guanylation by cyanamide and carbodiimides 8
1.3.1.3 Guanylation by isothiourea 9
1.3.1.4 Guanylation by chloroformamidinium chloride 9
1.3.2 Guanidine synthesis by guanidinylation reaction mechanism 10
1.3.2.1 Synthesis from alkyl halide 10
1.3.2.2 Synthesis from α-chlorocinnamonitrile 10
1.3.2.3 Solvent free synthesis 10
1.3.3 Some other methods for guanidine synthesis 11
1.3.3.1 Microwave-assisted synthesis 11
1.3.3.2 Synthesis of cyclic guanidine using cyanogen bromide 12
1.3.3.3 Synthesis from aminoiminomethansulfonic acids 12
1.4 Coordination chemistry of guanidines 12
1.5 Coordination chemistry of copper 15
1.6 Biomolecules and copper 16
1.7 Copper complexes of guanidines 16
Page
1.8 Guanidines as anti-cancer agents 17
1.9 Guanidines as antioxidant agents 20
1.10 Guanidines as anti-biotic agents 21
1.11 Guanidines as anti-fungal agents 22
1.12 Aims of study 23
References 23
Chapter-2 Experimental and Characterization 31-75
2.1 Chemicals 31
2.2 Instrumentation 31
2.3 Synthesis of pre-ligand (N,N΄-disubstituted thioureas) 32
2.4 Synthesis and characterization of guanidine ligands 33
2.4.1 General synthetic route for guanidine ligands 33
2.4.2 Synthesis and characterization of N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-
phenylguanidines (a1-a28)
34
2.4.3 Synthesis and characterization of N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-
pyridylguanidines (b1-b29)
47
2.5 Synthesis and characterization of Cu(II) complexes of guanidines 60
2.5.1 General synthetic route for Cu(II) complexes of guanidines 60
2.5.2 Synthesis and characterization of Bis(N-pivaloyl-N΄-(alkyl/aryl)-
N˝-phenylguanidinato)copper(II) complexes (A1-A28)
61
2.5.3 Synthesis and characterization of Bis(N-pivaloyl-Nʹ-(alkyl/aryl)-
Nʺ-pyridylguanidinato)copper(II) complexes (B1-B29)
66
2.6 Synthesis and characterization of Ni(II) complexes of guanidines 73
2.6.1 Synthesis and characterization of Bis(N-pivaloyl-N΄-(alkyl/aryl)-
N˝-phenylguanidinato)nickel(II) complexes (Nia1-Nia9)
73
References 75
Chapter-3 Results and Discussion 76-97
3.1 Elemental analysis 76
3.2 FT-IR spectroscopy 76
3.3 Multi-nuclear (1H, 13C) NMR spectroscopy 77
3.4 Magnetic susceptibility 78
3.5 Single crystal X-ray diffraction analysis 79
Page
3.5.1 Crystal structures of guanidines (Ligands) 79
3.5.2 Single crystal X-ray studies of copper(II) complexes 89
3.5.3 Single crystal X-ray studies of bis(N-pivaloyl-Nʹ,Nʺ-
diphenylguanidinato)nickel(II) (Nia1)
94
References 96
Chapter-4 Biological Screening 98-112
4.1 Biological assay 98
4.2 Cytotoxicity 98
4.2.1 Brine shrimps (Artemia salina) lethality assay 98
4.2.2 Potato disc anti-tumor assay 100
4.3 Anti-oxidant study 103
4.4 Antifungal activity 105
4.5 Antibacterial activity 107
References 110
Conclusions 111
Future plans 112
i
Acknowledgements
All praises to Almighty Allah, Creator of the universe, most beneficent and
merciful. He, Who blessed me with potential and ability to complete this research work.
Peace and blessing of Allah be upon the Holy Prophet Muhammad (PBUH) and his
pious progeny, who is the source of knowledge and guidance for the entire world
forever.
I wish to express enthusiastic thanks to Prof. Dr. Amin Badshah (TI) my
affectionate Supervisor and Chairman, Department of Chemistry, Quaid-i-Azam
University, Islamabad, for his enthusiastic interest & keen supervision and all time
facilitating nature. I admire him for his strive for perfection and his genuine concern for
the well-being of his students.
I am extremely thankful to Prof. Dr. Saqib Ali (PoP), Head of
Inorganic/Analytical Section, Department of Chemistry, Quaid-i-Azam University,
Islamabad, for his friendly behavior and cheering attitude. The valuable co-operation of
my Respected Teachers in the Department of Chemistry, QAU will remain alive in my
memory forever. I am highly obliged to Prof. Dr. Davit Zargarian, Department de
Chimie, Universite de Montreal, Canada, for providing the research opportunity under
his kind supervision during my stay in Canada.
I would also like to extend a wholehearted thanks to Prof. Frederic-Georges
Fontaine, Dr. Danis Spasyok, Dr. Eva Freisinger, Ms Berlin and Mr. Boris Vibrio for
providing single crystal analysis facilities. I would like to express my deepest gratitude
to Dr. Bushra Mirza, Mr. Naseer Ali Shah, Mr. Siraj-ud-Din and Mr. Momin Khan for
conducting the biological screening of synthesized compounds and Dr. Moazzam
Hussain Bhatti for providing the facilities of magnetic susceptibility measurements.
I am gratified to my seniors Dr. Khawar Rauf, Dr. Niaz Muhammad, Dr. Zia-
ur-Rehman, Dr. Shafqat Nadeem, my lab fellows Dr. Ghulam Murtaza, Dr. Hizbullah
Khan, Mr. Shafiqullah Marwat, Mr. Irshad Hussain, Dr. Ataf Ali Altaf, Mr. Jamil
Ahmed, Dr. Bhajan Lal, Mr. Azadar Hussain, friends and colleagues Dr. Noor-ul-
Amin, Dr. Muhammad Ibrahim, Dr. Amir Badshah, Mr. Hasib-ur-Rehman, Mr.
Adnan Siddique, Mr. Ishtiaq Khan, Mr. Khalid Mehmood, Mr. Ishaq Ali Shah and Mr.
Khurram Shahzad for their precious suggestions, assistance and fabulous company.
ii
I feel an immense pleasure to say thanks to all the technical staff of Chemistry
Department, Quaid-i-Azam University, Islamabad, Mr. Sharif Chohan, Mr. Shamsh
Pervaiz Mr. Tayyab, Mr. Farhan, Mr. G. Mustafa, Mr. Ali Zaman, and Mr. Faheem
for their kind help and sincere services. I highly appreciate Higher Education
Commission (HEC) of Pakistan for International Research Support Initiative Programme
(IRSIP) and Indigenous Scholarship for PhD degree.
From the bottom of my heart I am thankful to my parents, brothers and sisters
for their prayers, encouragement, excessive generosity and support over the years. I do
not have enough words to thank my wife for her love, patience and caring attitude and
children Murtaza Khan, Yumna Khan and Mustafa Khan for their sweet prayers.
Without the valuable contributions from my all well wishers the completion of this
venture could not have been possible.
Muhammad Said
iii
List of Figures
Figure Title Page
1.1 Some naturally occurring guanidine based biomolecules 1
1.2 Resonance structures of conjugate acid of guanidine 1
1.3 Structures of synoxazolidinone C and saxitoxin (STX) 2
1.4 Some important antihypertensive drugs 3
1.5 Structures of guanidine containing antihistamines 3
1.6 Guanidine containing antihyperglycemic and anti-obesity drugs 4
1.7 Structure of streptomycin 4
1.8 Structures of guanidine containing anti-inflammatory drugs 4
1.9 Structure of zanamivir 5
1.10 Benzothizole guanidines as anticoagulant 5
1.11 Cyanosilylation of ketones by polystyrene-supported 1,5,7-
Triazabicyclo[4,4,0]dec-5-ene
6
1.12 Guanylation of amine by thiourea in the presence of mercury(II)
chloride
7
1.13 Guanylation by thiourea in the presence EDCI and HMDS 7
1.14 Guanylation of amine by cyanamide in the presence of
hexafluoroisopropanol
8
1.15 Guanylation of chiral amine by carbodiimide using n-butyllithium 8
1.16 Guanylation of amine by carbodiimide in presence of ZnO used as
heterogeneous catalyst
8
1.17 Guanylation of amine by S-alkyl isothiourea in presence of HgCl2 9
1.18 Guanylation of amine by chloroformamidinium chloride (Vilsmeier salt) 9
1.19 Guanidinylation of alkyl halides in presence of sodium hydride 10
1.20 Guanidinylation of α-chlorocinnamonitrile 10
1.21 Solvent free guanidinylation for heterocyclic synthesis 11
1.22 Synthesis of protected guanidine through microwave assisted process 11
1.23 Synthesis of six and seven membered cyclic guanidines 12
1.24 Guanidine synthesis from aminoiminomethanesulfonic acid derivatives 12
1.25 Coordination compounds of bicyclic guanidines with different metals 13
1.26 Complexes of guanidinopyrimidine and dialkylphosphorylguanidines 13
iv
1.27 Structures of guanidinate complexes 14
1.28 Structures of bicyclic guanidinate complexes 14
1.29 Cobalt complexes with guanidinates having additional donor atoms 14
1.30 Distorted square pyramidal (a) and square planer (b) complex of Cu(II) 15
1.31 Structure of [Cu(II)(1-amidino-O-2-methoxyethyl urea)2]Cl2 16
1.32 Structures of hydroxo and oxo bridging copper(II) complexes 16
1.33 Structure of anionic cyclic guanidinate copper(I) dihalide 17
1.34 Structure of guanidines having pyrolidine and 2-aminoimidazole 17
1.35 Structures of polycyclic guanidine alkaloids 18
1.36 General structure of (2-(arylthio)benzylideneamino)guanidines 18
1.37 Structures of thiophene-fused tetracyclic analogues of ametantrone 19
1.38 Structures of derivatives of 7-aryl-2-pyridyl-6,7-dihydro[1,2,4]triazolo
[1,5-a][1,3,5]triazin-5-amines
19
1.39 Structures of triazolobenzothiadiazine-pyrrolobenzodiazepines (A)
general structure, (B) and (C) active compounds.
20
1.40 Structure of Mirabiline 21
1.41 Structure of 11- guanidinodrimene 22
1.42 Structures of massadine and naamine G 22
2.1 Scheme for synthesis of thioureas 32
2.2 General scheme for synthesis of guanidines 33
2.3 Synthesis scheme for N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-phenylguanidines
from N-pivaloyl-Nʹ-phenylthiourea
34
2.4 Synthesis scheme for second series of guanidines from N-pivaloyl-Nʹ-
pyridylthiourea
47
2.5 General scheme for synthesis of guanidinatocopper(II) complexes 60
2.6 Synthesis scheme for bis(N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-phenylguani-
dinato)copper(II) complexes
61
2.7 Synthesis scheme for bis(N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-pyridylguani-
dinato)copper(II) complexes
67
2.8 Synthesis scheme for bis(N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-phenylguani-
dinato)nickel(II) complexes
73
3.1 (a) Diagram of a1 with atomic numbering scheme. (b) Diagram of a1
showing intramolecular hydrogen bondings
80
v
3.2 (a) Diagram of a4 with atomic numbering scheme. (b) Diagram of a4
showing intramolecular hydrogen bondings
81
3.3 (a) Diagram of a5 with atomic numbering scheme. (b) Diagram of a5
showing intramolecular hydrogen bondings
82
3.4 Diagram of a13 with atomic numbering scheme 83
3.5 (a) Diagram of b7 with atomic numbering scheme. (b) Diagram of b7
showing intramolecular hydrogen bondings
84
3.6 (a) Diagram of b29 with atomic numbering scheme. (b) Diagram of b29
showing intramolecular hydrogen bondings
85
3.7 Diagram of A6 with atomic numbering scheme 90
3.8 Diagram of A15 with atomic numbering scheme 91
3.9 Diagram of A20 with selected atomic numbering scheme 92
3.10 Diagram of Nia1 with atomic numbering scheme 95
4.1 Graphical representation showing percent scavenging of DPPH by some
guanidines and their copper(II) complexes at various concentrations and
time intervals
103
vi
List of Tables
Table Title Page
3.1 Crystal data and structure refinement parameters for a1, a4, a5, and a13 86
3.2 Crystal data and structure refinement parameters for b7 and b29 87
3.3 Selected bond lengths, bond angles and torsion angles for guanidines 88
3.4 Crystal data and structure refinement parameters for A6, A15 and A20 93
3.5 Selected bond lengths, bond angles and torsion angles for Cu(II)
complexes
94
3.6 Crystal data and structure refinement parameters for Nia1 95
3.7 Selected bond lengths, bond angles and torsion angles for Nia1 96
4.1 Brine shrimps lethality assay for selected guanidines and their
copper(II) complexes
99
4.2 Potato disc antitumor assay of selected guanidines and their copper(II)
complexes
102
4.3 Antifungal activity of selected guanidines and their copper(II)
complexes
106
4.4 Antibactrial activity of selected guanidines and their copper(II)
complexes
108
vii
Abstract
Two series of pivaloyl substituted guanidines were synthesized from N-pivaloyl-Nʹ-
phenylthiourea and N-pivaloyl-Nʹ-(2-pyridyl)thiourea respectively and fully
characterized by elemental analysis, FT-IR spectroscopy, multinuclear NMR (1H, 13C)
and single crystal X-ray diffraction techniques. The copper(II) complexes and some
nickel(II) complexes of these guanidines were also synthesized and characterized.
Coordination chemistry of the pivaloyl substituted guanidines depends on the
substituents attached with the CN3 moiety, inductive effect and steric hindrance created
by the substituents. The synthesized guanidines act as bidentate chelating ligands which
coordinate with Cu(II) and Ni(II) through the oxygen atom of the carbonyl group and a
nitrogen atom of the guanidine moiety. The geometry around the metal centre is pseudo
square planar and the metal to ligand ratio is 1:2. Some of the synthesized compounds
were screened for anticancer assay using the potato disc method which shows that
guanidine ligands have significant antitumor activities which are further enhanced by the
complexation with Cu(II). The DPPH scavenging assay for some selected compounds
was conducted, showing good antioxidant activity for ligands which is suppressed by
complexation. Antifungal and antibiotic activities of the synthesized guanidines are
insignificant. The antibacterial properties of the free ligands are further reduced by
complexation.
1
Chapter-1
Introduction
1.1 Introduction
Guanidines are organic compounds having a planar Y shaped CN3 group. Guanidines
are building blocks of several biomolecules such as guanine, arginine and creatine
phosphate [1]. These are physiologically highly active substances having a wide
spectrum of activities including anticancer [2], antidiabetic [3], antiviral, anti-
inflammatory [4], antibiotic [5], antileishmenial [6], antiprotozoal, antihistaminic and
antihypertensive [7] properties. Such a diverse range of biochemical behavior of this
class of compounds can be attributed to the open structure of the guanidine moiety at
which various substituents can be attached to the nitrogen atoms. The introduction of
a guanidinium group to other drugs having low penetration through different
membranes in the body, increases their ability to cross biological barriers and thus
enhance their biological activity [8].
Figure 1.1: Some naturally occurring guanidine based biomolecules
The guanidine unit has three nitrogen atoms and exhibits the strongest Bronsted
basicity among amine derivatives (i.e. amine and imine). The strongest basicity of
guanidine is due to the resonance stability of its conjugate acid [C(NH2)3]+ which is
stabilized by the delocalization of pi electrons across the almost symmetrical CN3
unit, the phenomenon described by the term Y-aromaticity [9].
Figure 1.2: Resonance structures of conjugate acids of guanidine
The introduction of a substituent on any nitrogen of guanidine markedly changes its
basicity. The basicity of guanidine is increased by the introduction of electron
donating groups and vice versa. The pKa of unsubstituted guanidine is 12.6 while that
2
of benzoylguanidine, phenylguanidine, tetramethylguanidine, pentamethylguanidine
and heptamethyguanidine are 6.98, 10.77, 13.6, 15.6 and 17.1 respectively [10]. The
substituted guanidines are commonly known as super bases due to their strong
basicity and are used in organic synthesis.
1.2 Applications of guanidines
There are numerous applications of guanidines in the field of chemistry and biology.
The most important ones are described:
1.2.1 Naturally occurring guanidine compounds
There is a large number of naturally occurring guanidines with diverse importance
e.g. guanine is a nitrogenous base present in the nucleotide of DNA while arginine is
an amino acid. Synoxazolidinone C isolated from the sub-arctic ascidian Synoicum
pulmonaria is a potent antibacterial and anti-cancer agent [11]. Saxitoxin (STX)
produced by dinoflagellates are potent neurotoxins which are the causative agents of
paralytic shellfish poisoning [12].
Figure 1.3: Structures of synoxazolidinone C and saxitoxin (STX)
1.2.2 Guanidine based pharmaceutical compounds
a. Antihypertensive drugs
All the common classes of antihypertensive drugs contain the guanidine group. i)
Amiloride and Triamterene are potassium sparing diuretics that promote the loss of
sodium and water from the body without depleting potassium, to reduce blood
pressure. ii) Doxazosin mesylate and Prazosin are alpha blockers that lower the blood
pressure by relaxing blood vessels. iii) Clonidine, guanabenz, guanethidine,
moxonidine and guanfacine lower the blood pressure by activating alpha receptors in
the central nervous system which open the peripheral arteries and pressure is reduced
[13].
3
Figure 1.4: Some important antihypertensive drugs
b. Drugs for central nervous system
During Alzheimer’s disease β-amyloid (Ab) is produced due to the protolytic
cleavage of the amyloid precursor protein by β-secretase (BACE-1) and γ-secretase.
Acylguanidine derivatives inhibit BACE-1 and have therapeutic potential for treating
Alzheimer’s disease [14].
c. Antihistamines
The guanidine based antihistaminic drugs famotidine and cimetidine are in common
practice for the treatment of ulcer and other related gastric disorders while epinastine
is used in eye drops for the treatment of allergic conjunctivities.
Figure 1.5: Structures of guanidine containing antihistamines
d. Antihyperglycemic and anti-obesity drugs
N-(cyclopropylmethyl)-N΄-(4(aminomethyl)cyclohexylmethyl)guanidine is a potential
antihyperglycemic and food intake-reducing agent and can be useful against obesity
4
[15]. Metformin, phenformin and 3-guanidinopropionicacid, benzylguanidine and its
various derivatives are potent weight reducing agents and are useful in diet induced
obesity [16].
Figure 1.6: Guanidine containing antihyperglycemic and anti-obesity drugs
e. Antibiotic drugs
Streptomycin is a guanidine based broad spectrum antibiotic mostly prescribed by the
physicians against resistant strains.
Figure 1.7: Structure of streptomycin
Pyrrolidine bis-cyclic guanidines are potent bacteriostatic and bactericidal agents
against human pathogen methicillin-resistant Staphylococcus aureus and vacomycin-
resistant Enterococcus faecalis [17].
f. Anti-inflammatory drugs
Amidinohydrazones such as 2-[(4-anilino-3-cyano-2-oxo-1,2-dihydropyridine-5-yl)-
methylidene]aminoguanidine and its analogs are potent anti-inflammatory and
antihypertensive compounds [18]. N1,N2-diisopentenylguanidine and N1,N2,N3-
triisopentenylguanidine extracted from African plant Alchornea cordifolia have
shown good anti-inflammatory properties [19]. Methylguanidine have also shown
substantial reduction of acute inflammation [20].
Amidinohydrazones, N1,N2-diisopentenylguanidine N1,N2,N3-triisopentenyl
guanidine Figure 1.8: Structures of guanidine containing anti-inflammatory drugs
5
g. Antiprotozoal drugs
Triaryl bisguanidine have shown good antiprotozoal activity in vitro models against
Trypanosoma brucei rhodesiense and Plasmodium falciparum [21].
h. Influenza inhibitor
Neuraminidase is an influenza viral enzyme which plays an important role in viral
replication process. Compounds inhibiting the enzymatic activity of neuraminidase
(neuraminidase inhibitors) are used as anti-influenza drugs. Zanamivir and some other
guanidine containing compounds are neuraminidase inhibitors and are used as anti-
influenza drugs [22].
Figure 1.9: Structure of zanamivir
i. Anticoagulant
The blood coagulation process is one of the main issues in thrombosis (blood clot
formation in blood vessels) and hence its prevention is highly necessary. Benzothizole
guanidines act as thrombin and trypsin (IV) inhibitors and are potent anticoagulants
[23]. Acylguanidine derivatives have also good anticoagulant properties [24].
Figure 1.10: Benzothizole guanidines as anticoagulants
1.2.3 Paper and membranes with antibacterial activity
Guanidine polymers are used in cellulose papers having high wetting strength and anti
bacterial properties [25]. The sorption of guanidine oligomers on hydrophobic
membranes such as polyethylene terephthalate (PET) track membranes and give them
6
bactericidal properties which increase their operational life and also improve the
quality of products passing through such membranes [26].
1.2.4 Catalyst for organic synthesis
Guanidine derivatives have been used as efficient organocatalysts for Henry reactions
and Knoevenagel condensation reaction [27]. In the presence of guanidine catalysts,
these reactions proceed at room temperature and do not need anhydrous solvents or
reagents and inert atmosphere. Matsukawa et al. reported that polystyrene-supported
1,5,7-triazabicyclo[4,4,0]dec-5-ene (PS-TBD) as an important and efficient catalyst
for the cyanosilylation of ketones, imines and aldehydes [28].
Figure 1.11: Cyanosilylation of ketones by polystyrene-supported 1,5,7-
triazabicyclo[4,4,0]dec-5-ene
Alsarraf et al. reported that cyclic guanidines are efficient organocatalysts for
the synthesis of polyurethanes [29].
1.2.5 Uses of guanidine salts
Guanidine nitrate is a gas generating agent and is used along with a propellant such as
3-nitro-1,2,4-triazole-5-one (NTO) for military purposes [30]. Guanidine
hydrochloride is used as catalyst in Mannich reactions to occur at room temperature
and solvent free conditions [31].
1.3 Synthetic strategies for substituted guanidines
The synthesis of substituted guanidines is an active field in modern research due to
the promising pharmacological results shown by natural and synthetic compounds
belonging to this class. The synthetic strategies for substituted guanidines can be
classified into two main divisions i.e. guanylation and guanidinylation [32]. In the
guanylation method, a new guanidine unit is produced during the reaction while in the
guanidinylation reaction, a new substituent is incorporated on an already present
guanidine unit.
7
1.3.1 Guanidine synthesis by guanylation reaction mechanism
The guanylation reaction involves the attachment of a guanyl group –C(=NH)NR2 to
an amine [33]. The nucleophilic amine reacts with an electrophilic amidine or
carbodiimide species and generates a new guanidine unit. Generally a more
electrophilic amidine, having a better leaving group, can be easily displaced by an
incoming amine. The carbamate protected guanylating reagents are preferred to
directly synthesize protected guanidines which are less polar as compared to non-
protected guanidines and can be easily purified by chromatographic techniques. Some
important methods for the synthesis of guanidine via a guanylation reaction
mechanism are the following:
1.3.1.1 Guanylation by thiourea
The most commonly used method for synthesis of the guanidine is based on the
nucleophilic attack of a primary or secondary amine on the electrophilic center of
thiourea in the presence of mercury(II) chloride and an excess of triethylamine [34].
The generalized scheme for this reaction is given as:
Figure 1.12: Guanylation of an amine by thiourea in the presence of mercury(II)
chloride
This method is particularly very effective in the case of thiourea having at least one
conjugating substituent e.g. carbonyl, sulphonyl or aryl group on the nitrogen atom
[35].
The use of Bi(NO3)3.5H2O is also reported for the synthesis of guanidine from
thiourea which is more environment friendly and it is as efficient as in the case of
HgCl2 but the reaction proceeds slowly [36]. EDCI (1-(3-dimethylaminopropyl)-3-
ethylcarbodiimide hydrochloride is another important coupling reagent used for the
synthesis of acyl guanidines [37]. Shinada et al. reported the synthesis of N-acyl-N΄-
substituted guanidines using EDCI [38]. Hexamethyldisilazane (HMDS) is used as a
nitrogen source in this reaction.
Figure 1.13: Guanylation by thiourea in the presence EDCI and HMDS
8
Microwave radiations are used by H. Marquez et al. for the solvent free
synthesis of guanidine from thiourea derivatives [39]. The use of quaternary
ammonium permanganate for the synthesis of guanidine from thiourea in the presence
of an amine is also reported [40].
1.3.1.2 Guanylation by cyanamide and carbodiimides
Cyanamides and carbodiimides are very important guanylating agents for the
guanidine synthesis [41]. Cyanamide reacts with an amine in the presence of
hexafluoroisopropanol to produce guanidine in a good yield [42].
Figure 1.14: Guanylation of an amine by cyanamide in the presence of
hexafluoroisopropanol
This method is also used for the synthesis of monosubstituted N-
hydroxyguanidines [43]. Cohn et al. reported the synthesis of chiral guanidine from a
chiral amine using carbodiimide. The chiral amines are first reacted with n-
butyllithium to form lithium amides, and then with carbodiimide to form lithiated
products that give guanidine after hydrolysis [44].
Figure 1.15: Guanylation of a chiral amine by carbodiimide using n-butyllithium
N,N΄,N˝-trisubstituted guanidines have been directly synthesized by the
reaction of amines with carbodiimides in the presence of ZnO used as heterogeneous
catalyst [45]. This approach is successful for converting various aliphatic, aromatic
and heterocyclic amines to guanidines.
Figure 1.16: Guanylation of an amine by carbodiimide in the presence of ZnO used
as heterogeneous catalyst
9
1.3.1.3 Guanylation by isothiourea
Guanidines can be synthesized by guanylation reactions of primary and secondary
amines with S-alkyl isothiourea in the presence of HgCl2 and Et3N; e.g BOC
protected guanidines are produced from N1,N2-Bis(BOC)-S-methyl isothiourea [46].
Figure 1.17: Guanylation of an amine by S-alkyl isothiourea in the presence of HgCl2
This method is also used for the synthesis of cyclic guanidines; e. g. 1,3-
diamino-benzyloxycarbonyl protected methyl isothiourea reacts with alkyldiamines
and produces imino-protected cyclic guanidine [47]. Microwave assisted conditions
are also reported for the synthesis of cyanoguanidine using this method [48].
1.3.1.4 Guanylation by chloroformamidinium chloride
Chloroformamidinium chloride (Vilsmeier salt) reacts with an amine under basic
conditions and produces guanidine. This method is especially useful for the synthesis
of guanidine-amine-hybrid compounds [49].
Figure 1.18: Guanylation of an amine by chloroformamidinium chloride (Vilsmeier
salt)
The condensation reaction of chloro-(dialkylamino)-dialkylmethanaminium
chloride with an amine produces guanidine; e.g 1-chloro-1-(dimethylamino)-N,N-
dimethylmethanaminium chloride reacts with quinolin-8-amine to produce N-(1,3-
dimethylimidazolidin-2-yliden)quinolin-amine [50].
10
1.3.2 Guanidine synthesis by guanidinylation reaction mechanism
Reactions which involve the attachment of a guanidine moiety (–NH(C=NH)NR2) to
the carbon atom are referred as guanidinylation reactions. In these reactions
guanidines are further functionalized to obtain highly substituted guanidines. Some
important guanidinylation methods are given below:
1.3.2.1 Synthesis from alkyl halides
The guanidinylation of alkyl halides in the presence of sodium hydride produces
further substitutions on guanidine. Vaidyanathan et al. reported that these conditions
are useful only for primary alkyl halides while secondary alkyl halides undergo
elimination reactions under these conditions [51].
Figure 1.19: Guanidinylation of alkyl halides in the presence of sodium hydride
Xing et al. reported the synthesis of symmetrical and unsymmetrical N,N΄-
diaryl guanidines from guanidine nitrate using CuI and N-methylglycine as catalysts
[52]. H. Hammoud et al. reported a direct guanidinylation of alkyl and heteroaryl
halides via copper catalyzed cross coupling reactions [53].
1.3.2.2 Synthesis from α-chlorocinnamonitrile
The 2,4-diamino-6-arylpyrimidines are produced by the reaction of α-
chlorocinnamonitrile with guanidine [54].
Figure 1.20: Guanidinylation of α-chlorocinnamonitrile
1.3.2.3 Solvent free synthesis
Heterocyclic guanidine derivatives such as 4-aryl-6-(pyridine-2-yl)pyrimidin-2-amin
can be synthesized in one pot reaction by an environmental friendly solvent free
reaction of an aromatic aldehyde, 2-actylpyridine and guanidine carbonate in high
yields [55].
11
Figure 1.21: Solvent free guanidinylation reaction
1.3.3 Some other methods for guanidine synthesis
1.3.3.1 Microwave-assisted synthesis
Highly functionalized guanidines can be synthesized by microwave assisted methods
using soluble polymer support. Monohydroxyl functionalized polyethylenglycol is
reacted with 4-chloromethylbenzoyl chloride to develop a polymer conjugate having
ester bonds. Then piperazinyl or diazepanyl moieties are introduced through
nucleophilic substitution reactions to obtain a PEG attached benzyldiamine which
further reacts with guanilating reagents such as thiourea, isothiourea, triflylguanidine,
carboxamidine to form a PEG linked guanidine. Finally, the polymer support is
cleaved by using a methanolic solution of potassium cyanide to give substituted
guanidine derivatives [56]. The overall synthesis scheme is given in figure 1.22.
Figure 1.22: Synthesis of protected guanidine by a microwave assisted process
12
1.3.3.2 Synthesis of cyclic guanidines using cyanogen bromide
Cyclic guanidines (with 6 or 7 membered rings) can be synthesized by the reaction of
isatoic anhydride with primary amines and hydrazines to obtain 2-aminobenzamide
and 2-amionbenzohydrazide followed by reaction with cyanogens bromide [57]. The
reaction scheme is given in figure 1.23.
Figure 1.23: Synthesis of six and seven membered cyclic guanidines
1.3.3.3 Synthesis from aminoiminomethansulfonic acids
Aminoiminomethanesulfonic acid derivatives undergo reactions with
hydroxylaminehydrochloride in the presence of triethylamine and produce N-
hydroxylguanidine [58].
Figure 1.24: Guanidine synthesis from aminoiminomethanesulfonic acid derivatives
1.4 Coordination chemistry of guanidines
The strong basicity of guanidines and the formation of guanidinium cations in
aqueous solution, which has negligible coordination ability, had made them less
attractive to be used as ligands for many years. However, in the last two decades,
guanidines have been used successfully as ligands and their complexes with various
metals have been reported. Their coordination behavior is mainly of two types, i.e. as
a neutral ligand (guanidines) or as an anionic ligand (guanidinates). There are also
many reports describing complexes in which guanidine acts as a counter ion in the
form of a guanidinium cation [59]. Complexes containing neutral guanidines having
no other donor atoms are reported as monodentate ligands with various metals such as
Cu(II), Zn(II), Al(III), Pt(II), Pd(II), Co(II), Ni(II), Au(I), Ag(I), Tc(V) and Cr(III)
13
[60]. Bicyclic guanidine, e. g. 1,3,4,6,7,8-hexahydro-2H-pyrimido-[1,2-a]pyrimidine,
acts as a monodentate ligand with different metals [61]. Some of the reported
coordination compounds of bicyclic guanidine are given in figure 1.25.
Figure 1.25: Coordination compounds of bicyclic guanidines with different metals
Substituted guanidines containing additional donor atoms (N, O or S) can act
as chelating ligands coordinating through the nitrogen atom of the guanidine moiety
and an additional donor site [62]. Guanidinopyrimidine and
dialkylphosphorylguanidines behave as chelating ligands having additional donor
atoms.
Figure 1.26: Complexes of guanidinopyrimidine and dialkylphosphorylguanidines
Recently, the coordination chemistry of deprotonated guanidines
(guanidinates) has flourished rapidly. Due to the electronic and structural flexibility of
guanidinates, they can form complexes with different metals in different oxidation
states. A large number of complexes having monoanionic (guanidinates(-1)) and
dianioninic (guanidinates(-2) have been reported with different metals e.g. Cu, Cd,
Pd, Pt, Li, K, Fe, Mn, Mg, Ba, Sr, Cr, Al, Sn, Sb, Ru, Mo, Os, Nb, Ru, Zr, Hf, Ti, Yb,
Sm, Ta, Ln, Y, Er, and Dy; perhaps from all metals of the periodic table. Among these
complexes the guanidinates generally act as bidentate ligands, coordinating through
two nitrogen atoms of the guanidine group forming four membered rings. The
bidentate anionic guanidinate ligands provide four electrons to the central metal atom
and the zwitterionic resonance contributes to the stability of complex [63]. Some
examples are given in figure 1.27.
14
Figure 1.27: Structures of guanidinate complexes
Bicyclic guanidinates also act as bidentate ligands and Mohamed et al. [64]
reported binuclear and tetranuclear complexes with gold. There are some examples
where guanidinates act as monodentate ligands such as binuclear complexes of
1,1,3,3-tetraalkylguanidinates with Zn.
Figure 1.28: Structures of bicyclic guanidinate complexes
In the presence of additional donor sites in substituted guanidines, only one
nitrogen atom of the guanidine moiety coordinates with the metal along with an
additional donor atom. Figure 1.29.
Figure 1.29: Cobalt complexes with guanidinates having additional donor atoms
As discussed earlier, the guanidines are highly therapeutically active
substances and their complexes with different metals have also shown good
physiological properties. Miodragovic et al. reported the synthesis of mixed
complexes of ethylenediamine and anti-ulcer drug famotidine with cobalt(III) which
has better selectivities and growth inhibition properties against pathogens as
compared with the drug alone [65]. A copper(II) complex of guanfacine, which is an
15
antihypertensive drug, is 30% more active than the pure drug [66]. Maffei et al.
reported copper(II) complexes with fluorinated α-hydroxycarboxylates as potent
antileishmanial agents [67].
1.5 Coordination chemistry of copper
Copper is an important transition metal, with the atomic number 29 in the periodic
table, playing a key role in the human development. It exists in different oxidation
states (I, II, III, IV) and it forms compounds having different geometries. There are
very few examples with copper in the oxidation state of III (e.g NaCuO2) and IV (e.g.
Cs2CuF6) [68]. In most cases it is present in the oxidation state of I and II in
coordination compounds with ligands having different coordination numbers. Cu(I) is
a d10 system forming a distorted tetrahedral geometry in the case of the coordination
number four [69] and a trigonal planar geometry in case of the coordination number
three [70].
Cu(II) is a d9 system and in the case of coordination number six it has an
octahedral geometry or a square bipyramidal geometry; e. g. [Cu(NH3)4(H2O)2]2+
around the metal center [71]. In case of coordination number five, Cu(II) forms a
square pyramidal [72] or a trigonal-bipyramidal geometry [73].
[Cu(pyimpy)(Cl)(ClO4)] has a distorted square pyramidal geometry in which ClO4
occupies an axial position [74]. In case of coordination number four, Cu(II) forms a
square planar or distorted tetrahedral geometry (e.g. Cs2[CuCl4]) depending on the
ligands attached [75]. Cu(II) complexes are mostly paramagnetic and blue or green in
color due to d-d transitions which absorb light with wavelengths in the range of 600-
900 nm [76].
a b
Figure 1.30: Distorted square pyramidal (a) and square planar (b) complexes of
Cu(II)
16
1.6 Biomolecules and copper
Copper is an essential element for living organisms and it plays a vital role in their
metabolism. Many bio-molecules contain copper, e.g. azurin which is an electron
transfer protein [77]. Copper acts as cofactor in many enzymes (cuproenzymes) which
are involved in a variety of metabolic reactions. Cytochrome C oxidase is a
respiratory enzyme involved in mitochondrial respiration [78]. Tyrosinase is involved
in catalyzing the melanin pigment production [79] while lysyl oxidase plays an
important role in the cross-linking of collagen [80]. Copper is also an integral part of
the copper-zinc superoxide dismutase which is an antioxidant enzyme involved in the
removal of superoxides. Copper containing nitrite-reductase reduces nitrites into nitric
oxide and nitrous oxide [81].
1.7 Copper complexes of guanidines
Square planar Cu (II) complexes of substituted guanidines such as [Cu(II)(1-amidino-
O-2-methoxyethyl urea)2]Cl2 have shown a partial or non-intercalative mode of
interaction in DNA binding studies [82]. The structure is given in figure 1.31.
Figure 1.31: Structure of [Cu(II)(1-amidino-O-2-methoxyethyl urea)2]Cl2
Binuclear Cu(II) complexes having hydroxo bridging ligands are also reported
having a square planar geometry around the copper center [83]. The structures of
hydroxo and oxo bridging copper(II) complexes are given in figure 1.32.
Figure 1.32: Structures of hydroxo and oxo bridging copper(II) complexes
Chiarella et al. reported anionic cyclic guanidinate copper(I) dihalides with a trigonal
planar geometry around the metal ion [84]. The structure is given in figure 1.33.
17
Figure 1.33: Structure of an anionic cyclic guanidinate copper(I) dihalide
1.8 Guanidines as anti-cancer agents
Cancer is the outcome of uncontrolled cell division in the body. Genetic mutation is
the major cause of cancer. However, different chemical species that interfere the
enzyme’s structure or activity are also responsible for cancer. Radiotherapy and
chemotherapy are commonly used for the destruction of affected cells. Many classes
of compounds including guanidines are active anticancer agents. Guanidines having
pyrolidine moiety as well as a 2-aminoimidazole ring have been studied for cytotoxic
activites against 12 human tumor cell lines. The best inhibitory activity was against
A-549 (lung carcinoma NSCL) cells having GI50 0.1 µM [85]. The structure of the
active compound is given in figure 1.34.
Figure 1.34: Structure of guanidines with a pyrolidine and 2-aminoimidazole moiety
Polycyclic guanidine alkaloids extracted from sponge Monanchora unguifera
i.e ptilomycalin A, batzelladines L, batzelladines M, dehydrobatzelladine C,
crambescidine 800 and batzelladine N were tested against 11 different cancer cell
lines (Structures in figure 1.35).
18
Figure 1.35: Structures of polycyclic guanidine alkaloids
Ptilomycalin A and crambescidine 800 showed significant growth inhibition of 11 cell
lines with GI50 values of 0.03–0.19 µg/mL. Batzelladine L exhibited good activity
against DU-145, IGROV, SK-BR3, leukemia L-562, PANCL, HeLa, SK-MEL-28,
A549, HT- 29, LOVO, and LOVO-DOX cell lines with GI50 values of 0.23–4.96
µg/mL while batzelladines M, N and dehydrobatzelladine C showed good activities
against all the 11 cell lines [86].
Zhang et al. reported that (2-(arylthio)benzylideneamino)guanidines are potent
apoptosis inducers. These compounds have shown good activities in the cell growth
inhibition assay [87]. The general structure of (2-
(arylthio)benzylideneamino)guanidines is given in figure 1.36.
Figure 1.36: General structure of (2-(arylthio)benzylideneamino)guanidines
Shchekotikhin et al. reported the guanidine derivatives of thiophene-fused tetracyclic
analogues of ametantrone having good cytotoxic activities against a variety of tumor
19
cell lines including isogenic drug-resistant counterparts, i.e. murine leukemia L1210,
T-lymphocyte cell lines Molt4/C8 & CEM, human leukemia R562 and its MDR
subline K562/4 that over express P-glycoprotein and colon carcinoma HCT116 and its
subline HCT116p53KO. The above determinants alter the response of cells to many
anticancer drugs including doxorubicin. These compounds are less active against
L1210, Molt4/C8 and CEM cell lines but A has a good activity against the K562/4
subline [88].
Figure 1.37: Structures of thiophene-fused tetracyclic analogues of ametantrone
Dolzhenko et al. synthesized a series of fluorinated derivatives of 7-aryl-2-
pyridyl-6,7-dihydro[1,2,4]triazolo[1,5-a][1,3,5]triazin-5-amines (Figure 1.38 A)
exhibiting a satisfactory cell growth inhibition against various cell lines. The most
active anticancer agent identified in this study was 2-(pyridine-3-yl)-7-(4-
trifluoromethylphenyl)-6,7-dihydro[1,2,4]triazolo[1,5-a][1,3,5]triazin-5-amine
(Figure 1.38 B) [89].
Figure 1.38: Structures of derivatives of 7-aryl-2-pyridyl-6,7-
dihydro[1,2,4]triazolo[1,5-a][1,3,5]triazin-5-amines
Different triazolobenzothiadiazine-pyrrolobenzodiazepine conjugates linked
through different alkane spacers are reported by Kamal et al. having a significant
cytotoxicity against most of the cell lines examined. These compounds have been
evaluated for their in vitro cytotoxicity against selected human cancer cell lines of
20
breast (Zr-75-1, MCF7), lung (A-549, HOP62), colon (Colo205), oral (AW13516,
AW8507, KB), cervix (SiHa), prostate (PC-3) and ovarian (A2780) origin. Compound
(A) displays GI50 values 1.83-2.38 µM against all tumor cell lines, and it is identified
as the most promising compound of this series. Compound (B) has the highest activity
(Gl50 0.22 µM against an AW8507 cell line, oral cancer) among all the compounds
tested against various cancer strains [90].
Figure 1.39: Structures of triazolobenzothiadiazine-pyrrolobenzodiazepines (A)
general structure, (B) and (C) active compounds.
1.9 Guanidines as antioxidant agents
Toxic oxidative reactions in biomolecules (e.g. nucleic acids, lipids, proteins and
DNA) are initiated by reactive oxygen species (ROS) which play an important role
during the physiological activities of living organisms. These species are constantly
produced as by-products of metabolic reactions in living organisms. The imbalance
between formation and scavenging of ROS can increase the concentration of these
oxidants, which is called oxidative stress. The state of oxidative stress has deleterious
effects on almost all tissues and can initiate or enhance the rate of pathological
conditions such as neurodegeneration, inflammation, aging process, cancer and
cardiovascular diseases [91]. Tissues having high oxygen consumption rates such as
the central nervous system are highly susceptible to oxidative damage under the
conditions of oxidative stress [92]. The progress of such chronic diseases can be
slowed down by the introduction of protective compounds, known as antioxidants,
which inhibit ROS formation or trap free radicals [93]. There are a large number of
natural and synthetic substances acting as antioxidants. Naturally occurring
substances, like vitamin C, vitamin E, phenolic acids, polyphenols, flavonoids,
coumarin and phytoestrogens have been extensively studied for their role in reducing
21
the oxidative damage. These antioxidants scavenge free radical like peroxide,
hydroperoxide or lipid peroxyl and inhibit degenerative diseases. Heterocyclic
guanidine derivatives have shown remarkable antioxidant properties for reducing the
oxidative stress, induced in the blood serum and brain tissue by superoxide dismutase
and catalase enzymes during ischemia-reperfusion, causing restoration of blood
supply and having neuroprotective role [94].
The antioxidant behavior of natural and synthetic substances can be studied by
different in vitro and in vivo models. The in vitro models include 1,1-diphenyl-2-
picrylhydrazyl (DPPH) scavenging assay [95], 2,2′-azinobis(3-ethylbenzothiazoline-
6-sulfonic acid (ABTS) assay, malondialdehyde (MDA) assay and thiobarbituric acid
reactive substances (TBARS) assay.
1.10 Guanidines as anti-biotic agents
The development of resistance to current antibacterials continues to be a
serious difficulty in the treatment of infectious diseases. Therefore the discovery and
development of new antibiotics has become a high priority in biomedical research.
Here we focus on the antibacterial agents of natural and synthetic origin having a
guanidine group.
Polycyclic guanidine alkaloids extracted from sponge Monanchora unguifera
i.e ptilomycalin A, batzelladines L, M, C, dehydrobatzelladine C and crambescidine
800, mirabilin B (Figure 1.40) and batzelladine N were also tested against various
bacteria. Batzelladines L and N were more potent against Mycobacterium tuberculosis
[86]. A dimeric bromopyrrole alkaloid, nagelamide G was isolated from the
Okinawan marine sponge Agelas sp. which exhibited antibacterial activity against M.
luteus, B. subtilis and E. coli, but weakly inhibited protein phosphatase 2 A (IC50=13
μM), thus suggesting that this enzyme may not be the main molecular target
responsible for the antibacterial activity of this compound [96].
Figure 1.40: Structure of mirabiline (other structures given in figure 1.35)
22
1.11 Guanidines as anti-fungal agents
There is a substantial rise in frequency of invasive fungal infections with the
increasing number of immunocompromised patients, such as those infected with HIV,
receiving cancer therapy, immunosuppressive therapy or treatment with broad-
spectrum antibiotics. The search for better antifungal compounds with increased
specificity for fungal enzymes has become an important research area in medicine.
11-Guanidinodrimene which was derived from the natural product drimenol is an
antifungal agent. This compound is active at a minimal inhibitory concentration
(MIC) of 32 µg/mL against Candida albicans which is an opportunistic fungus of the
intestinal tract [96].
Figure 1.41: Structure of 11- guanidinodrimene
A polycyclic alkaloid massadine derived from a marine sponge Stylessa aff.
Massa, inhibit fungal GGTase (IC50 =3.9µM) while imidazole alkaloid naamine G
extracted from sponge Leucetta chagosensis exhibited strong antifungal activity
against Cladosporium herbarum [97].
Figure 1.42: Structures of massadine and naamine G
23
1.12 Aims of the study
The basic aims for this research project were:
To synthesize new pivaloyl substituted guanidines and their square planar complexes
with Cu(II) and Ni(II).
To completely characterize the synthesized compounds by elemental analysis, FT-IR,
multinuclear NMR (1H, 13C) and single crystal XRD techniques.
To check the biological profile of synthesized compounds for antitumor, cytotoxicity,
anti-oxidant, antibacterial and anti-fungal activities.
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31
Chapter-2
Experimental and Characterization
2.1 Chemicals
All starting materials were purchased from Sigma-Aldrich, Fluka and Alfa-Aesar
(Johnson Matthey). Pivaloic acid, thionyl chloride, nickel(II) chloride, potassium
thiocyanate, mercury(II) chloride, copper(II) chloride, copper(II) acetate, 2-
aminopyridine, 4-chloroaniline, 2,4-dichloroaniline, 2,5-dichloroaniline, 3,4-
dichloroaniline, 3,5-dichloroaniline and p-toluidine were used as received without
further purification while aniline, triethylamine, n-butylamine, sec-butylamine,
dimethylamine, diethylamine, dibutylamine, dipropylamine, cyclohexylamine,
benzylamine, methylbenzylamine, N-methylaniline, 2-chloroaniline, 3-chloroaniline,
o-anisidine, m-anisidine and 2,3-dimethylaniline were purified before use. The
organic solvents such as dichloromethane, chloroform, acetone, alcohols and n-
hexane were distilled, purified and dried according to reported methods [1], saturated
with nitrogen, stored over molecular sieves 4Å and degassed before use.
2.2 Instrumentation
Melting points were determined using a Gallenkamp (UK) melting point apparatus
and all the values are uncorrected.
IR spectra were recorded in the range of 400-4000 cm-1 as KBr discs on Bio-
Rad Excalibur FT-IR Model FTS 3000 MX. The NICOLET 6700, Thermo Scientific
FT-IR spectrophotometer was used to record the spectra in the range from 200-400
cm-1 using ATR.
NMR spectra were recorded on Bruker AV-300 and AV-400 MHz
spectrometers using deuterated solvents. 1H NMR spectra were recorded at (300 and
400 MHz respectively) using CDCl3 (δ = 7.26 ppm from TMS) and C6D6 (δ = 7.16
ppm from TMS); 13C NMR spectra were recorded at (75 and 100 MHz respectively)
using CDCl3 (δ = 77.2 ppm from TMS) and C6D6 (δ = 128.1 ppm from TMS) [2]. The
splitting of proton resonances in 1H NMR spectra are defined as s = singlet, d =
doublet, t = triplet, q = quartet and m = multiplet etc.; while coupling constants are
reported in Hz.
32
CHNS analyses were performed on a Fisons EA1108 CHNS analyzer and a
LECO-183 CHNS analyzer while the percentage of metals in complexes was
determined by Atomic Absorption Spectrophotometer Perkin Elmer 2380. The
magnetic susceptibility of the complexes was determined by Magnetic Susceptibility
Balance Auto MSB.
The crystallographic data for some of the synthesized guanidines and
copper(II) complexes, was collected using different diffractometers such as Bruker
Microstar equipped with a Kappa Nonius goniometer and a platinum 135 detector,
Oxford diffraction Xcalibur R diffractometer equipped with Enhance (Mo) X-ray
source and graphite monochromator etc.
2.3 Synthesis of pre-ligand (N,N′-disubstituted thioureas)
The pre-ligands N-pivaloyl-N′-phenylthiourea and N-pivaloyl-N′-(2-pyridyl)thiourea
were synthesized by reported methods [3] which were used as starting materials for
the synthesis of guanidines. The reaction scheme is given in figure 2.1.
Figure 2.1: Scheme for the synthesis of thioureas
The pivaloic acid was reacted with thionyl chloride to obtain pivaloyl chloride. The
suspension of potassium thiocyanate in acetone was added to the reaction flask to
react with in situ pivaloyl chloride. The reaction mixture was heated for 20 minutes
and then stirred at room temperature for 1-2 hours to obtain pivaloyl isothiocynate.
The respective amine was added to this reaction mixture with continuous stirring to
get the desired thiourea. The reaction progress was monitored by TLC at regular time
intervals till the completion of reaction. The reaction mixture was poured into ice
cooled water to get the solid product and remove the impurities. Finally, the solid
thiourea (pre-ligand) was filtered and washed with deionized water. The thiourea
33
obtained was dried in air and recrystallized in methanol to give fine fibers which were
used as such in further reactions.
2.4 Synthesis and characterization of guanidine ligands
2.4.1 General synthetic route for guanidine ligands
The guanidine compounds were synthesized from N,N′-disubstituted thiourea by the
reported guanylation method using mercury(II) chloride [4]. The synthesis scheme is
given in figure 2.2.
R1 = Phenyl (a1-a28) & Pyridyl (b1-b29)
No R2 R3 No R2 R3
1 Phenyl H 16 2,5-dichlorophenyl H
2 2-chlorophenyl H 17 2,4-dichlorophenyl H
3 3-chlorophenyl H 18 3,4-dichlorophenyl H
4 4-chlorophenyl H 19 3,5-dichlorophenyl H
5 2-methoxyphenyl H 20 2,3-dimethylphenyl H
6 p-tolyl H 21 3-methoxyphenyl H
7 2-fluorophenyl H 22 tert-butyl H
8 Ethyl H 23 Methyl Methyl
9 n-propyl H 24 Ethyl Ethyl
10 n-butyl H 25 Phenyl Methyl
11 iso-propyl H 26 Benzyl Methyl
12 sec-butyl H 27 o-tolyl H
13 n-propyl n-propyl 28 Cyclohexyl H
14 n-butyl n-butyl 29 2-pyridyl H
15 Benzyl H
Figure 2.2: General scheme for the synthesis of guanidines.
34
Thiourea was treated with different amines in DMF in the presence of triethylamine
and mercury(II) chloride. At the completion of reaction, the reaction mixture was
diluted with dichloromethane and the suspension was filtered to remove the HgS
residue. The solvents were evaporated under reduced pressure from the filtrate. The
residue was dissolved in CHCl3/CH2Cl2 and washed with water (3-4 times). The
target compound was obtained by evaporating the solvent from the organic fraction,
further purification by column chromatography and recrystallization from a suitable
solvent.
2.4.2 Synthesis and characterization of N-pivaloyl-N′-(alkyl/aryl)-N″-
phenylguanidines (a1-a28)
N-pivaloyl-N′-phenylthiourea was mixed with the equimolar amount of the desired
amine in DMF and added to two equivalents of triethylamine. One equivalent of
mercury(II) chloride was added to the reaction mixture with vigorous stirring while
keeping the temperature below 5 °C using an ice bath. The ice bath was removed after
30 minutes and stirring was continued for 4-5 hours at room temperature. The
progress of the reaction was monitored by TLC till completion of the reaction. Then
dichloromethane was added to reaction mixture and the suspension was filtered
through a pad of silica gel to remove the HgS precipitates, formed as byproduct in the
reaction. The solvents from the filtrate were evaporated under reduced pressure. The
residue was redissolved in CH2Cl2, washed with water (3-4 times) and the organic
phase was dried over anhydrous MgSO4. The solvent was evaporated and the product
was purified by column chromatography. The synthesis scheme is given in figure 2.3.
Figure 2.3: Synthesis scheme for N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-phenylguanidines
from N-pivaloyl-Nʹ-phenylthiourea
The characterization data of the synthesized compounds in this series is given on the
coming pages.
35
2.4.2.1 N-pivaloyl-N′,N″-diphenylguanidine (a1)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.0 mL (10 mmol) aniline, 2.8 mL (20
mmol) triethylamine and 2.72 g (10 mmol) mercury(II)
chloride. Yield 2.25 g (76%); compound colorless; m. p.
86-87 ºC; FT-IR (KBr, cm-1): 3412, 3256, 3119, 3051,
2959, 1676, 1528, 1462, 1370, 1203, 974, 736; 1H NMR (300 MHz, CDCl3, 25 °C): δ
1.09 (s, 9H, COC(CH3)3), 6.97-7.14 (m, 4H, Ar-H), 7.27-7.41 (m, 5H, Ar-H & NH),
7.73-7.76 (m, 2H, Ar-H), 10.18 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 ºC): δ
26.9 (3C, COC(CH3)3), 40.4 (COC(CH3)3), 119.9 (2C), 122.5 (2C), 122.8, 123.4,
128.9 (2C), 129.8 (2C), 138.9, 141.1 (Aromatic-C), 159.9 (CN3), 178.7 (C=O); Anal.
Calcd. for C18H21N3O: (295.38); C, 73.19; H, 7.49; N, 13.58; Found: C, 72.89; H,
7.51; N, 13.45%.
2.4.2.2 N-pivaloyl-N′-(2-chlorophenyl)-N″-phenylguanidine (a2)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.1 mL (10 mmol) 2-chloroaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.44 g (74%); compound
colorless; m. p. 64-65 ºC; FT-IR (KBr, cm-1): 3425, 3270,
3130, 3043, 2965, 1620, 1471, 1359, 1207, 937, 728; 1H NMR (300 MHz, C6D6, 25
ºC): δ 1.18 (s, 9H, COC(CH3)3), 6.62-6.76 (m, 2H, Ar-H), 6.82-6.95 (m, 1H, Ar-H),
7.32-7.36 (m, 2H, Ar-H), 7.53-7.67 (m, 3H, Ar-H), 7.83-7.86 (m, 1H, Ar-H), 8.64 (s,
1H, NH), 12.78 (s, 1H, NH; 13C NMR (75 MHz, C6D6, 25 °C): δ 26.6 (3C,
COC(CH3)3), 40.2 (COC(CH3)3), 121.9, 122.7 (2C), 123.2, 123.5, 124.4, 127.6,
129.4, 130.0 (2C), 130.6, 141.4 (Aromatic-C), 147.4 (CN3), 178.4 (C=O); Anal.
Calcd. for C18H20N3OCl: (329.82); C, 65.55; H, 6.11; N, 12.74; Found: C, 65.32; H,
6.06; N, 12.82%.
2.4.2.3 N-pivaloyl-N′-(3-chlorophenyl)-N″-phenylguanidine (a3)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.1 mL (10 mmol) 3-chloroaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.37 g (72%); compound
colorless; m. p. 70-71 ºC; FT-IR (KBr, cm-1): 3432, 3247,
36
3138, 3063, 2961, 1615, 1563, 1456, 1383, 1085, 825, 763; 1H NMR (300 MHz,
C6D6, 25 ºC): δ 1.16 (s, 9H, COC(CH3)3), 6.28-6.33 (m, 1H, Ar-H), 6.75-6.84 (m, 1H,
Ar-H), 6.82-6.86 (m, 1H, Ar-H) 7.23-7.30 (m, 3H, Ar-H), 7.62-7.67 (m, 2H, Ar-H),
8.36 (s, 1H, NH), 8.45 (s, 1H, Ar-H), 12.59 (s, 1H, NH); 13C NMR (75 MHz, C6D6,
25 °C): δ 26.6 (3C, COC(CH3)3), 40.2 (COC(CH3)3), 118.0, 120.0, 121.1, 122.7 (2C),
123.5, 129.2, 130.0 (2C), 130.9, 134.9, 141.0 (Aromatic-C), 147.2 (CN3), 178.4
(C=O); Anal. Calcd. for C18H20N3OCl: (329.82); C, 65.55; H, 6.11; N, 12.74; Found:
C, 65.24; H, 6.09; N, 12.85%.
2.4.2.4 N-pivaloyl-N′-(4-chlorophenyl)-N″-phenylguanidine (a4)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.28 g (10 mmol) 4-chloroaniline, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.47 g (75%); compound
colorless; m. p. 83-84 ºC; FT-IR (KBr, cm-1): 3397, 3267,
3120, 3085, 2981, 1622, 1545, 1437, 1362, 1076, 834; 1H
NMR (300 MHz, C6D6, 25 ºC): δ 1.16 (s, 9H, COC(CH3)3), 6.87-6.92 (m, 3H, Ar-H),
7.07 (d, 2H, 3J = 8.6 Hz, Ar-H), 7.42 (s, IH, NH), 7.69 (d, 2H, 3J = 8.6 Hz, Ar-H),
7.89-7.91 (m, 2H, Ar-H), 10.66 (s, 1H, NH); 13C NMR (75 MHz, C6D6, 25 °C): δ 26.6
(3C, COC(CH3)3), 40.2 (COC(CH3)3), 120.2, 121.3 (2C), 122.7 (2C), 123.5, 124.2,
129.1 (2C), 130.0 (2C), 141.1 (Aromatic-C), 162.7 (CN3), 178.4 (C=O); Anal. Calcd.
for C18H20N3OCl: (329.82); C, 65.55; H, 6.11; N, 12.74; Found: C, 65.68; H, 6.17; N,
12.53%.
2.4.2.5 N-pivaloyl-N′-(2-methoxyphenyl)-N″-phenylguanidine (a5)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.14 mL (10 mmol) o-anisidine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.47 g (76%); compound
colorless; m. p. 89-90 ºC; FT-IR (KBr, cm-1): 3405, 3233,
3142, 3029, 2973, 1660, 1631, 1535, 1462, 1295, 835, 687; 1H NMR (300 MHz,
C6D6, 25 °C): δ 1.14 (s,, 9H, COC(CH3)3), 3.41 (s, 3H, OCH3), 6.56-6.58 (m, 1H, Ar-
H), 6.88-6.95 (m, 5H, Ar-H), 7.70 (s, 1H, NH), 7.34-7.37 (m, 2H, Ar-H), 9.34-9.36
(m, 1H, Ar-H), 11.27 (s, 1H, NH); 13C NMR (75 MHz, C6D6, 25 °C): δ 26.7 (3C,
COC(CH3)3), 40.2 (COC(CH3)3), 55.6 (OCH3), 110.2, 120.6, 121.3 (2C), 122.4,
37
123.0, 123.2, 130.0 (2C), 141.5, 148.1, 148.9 (Aromatic-C), 156.5 (CN3), 177.7
(C=O); Anal. Calcd. for C19H23N3O2: (325.40); C, 70.13; H, 7.12; N, 12.91; Found: C,
69.78; H, 7.18; N, 12.80%.
2.4.2.6 N-pivaloyl-N′-(p-tolyl)-N″-phenylguanidine (a6)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.07 g (10 mmol) p-toluidine, 2.8 mL (20
mmol) triethylamine and 2.72 g (10 mmol) mercury(II)
chloride. Yield 2.38 g (77%); compound colorless; m. p.
77-78 ºC; FT-IR (KBr, cm-1): 3427, 3265, 3159, 3020,
2932, 1615, 1570, 1480, 1357, 1072, 837, 758; 1H NMR (300 MHz, CDCl3, 25 °C): δ
1.31 (s, 9H, COC(CH3)3), 2.14 (s, 3H, Ar-CH3), 6. 42-6.45 (m, 2H, Ar-H), 6.98-7.03
(m, 3H, Ar-H), 7.67-7.71 (m, 4H, Ar-H), 8.01 (s, 1H, NH), 12.34 (s, 1H, NH); 13C
NMR (75 MHz, CDCl3, 25 °C): δ 21.3 (Ar-CH3), 26.9 (3C, COC(CH3)3), 40.7
(COC(CH3)3), 119.2, 122.3 (2C), 123.0, 130.0 (2C), 132.3 (2C), 132.8 (2C), 141.5,
148.1 (Aromatic-C), 158.8 (CN3), 178.2 (C=O); Anal. Calcd. for C19H23N3O:
(309.40); C, 73.76; H, 7.49; N, 13.58; Found: C, 73.57; H, 7.37; N, 13.62%.
2.4.2.7 N-pivaloyl-N′-(2-fluorophenyl)-N″-phenylguanidine (a7)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.10 mL (10 mmol) 2-fluoroaniline, 22.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.16 g (69%); compound
colorless; m. p. 91-92 ºC; FT-IR (KBr, cm-1): 3447,
3209, 3122, 3081, 2975, 1623, 1551, 1465, 1371, 1087, 805; 1H NMR (300 MHz,
CDCl3, 25 °C): δ 1.39 (s, 9H, COC(CH3)3), 6.69-6.73 (m, 3H, Ar-H), 7.13-7.22 (m,
4H, Ar-H), 7.91-7.97 (m, 2H, Ar-H), 8.18 (s, 1H, NH), 10.92 (s, 1H, NH); 13C NMR
(75 MHz, CDCl3, 25 °C): δ 28.1 (3C, COC(CH3)3), 41.3 (COC(CH3)3), 119.8, 122.5
(2C), 124.3, 126.9, 129.2 (2C), 133.4, 135.2, 141.3, 143.7, 149.6 (Aromatic-C), 160.2
(CN3), 181.8 (C=O); Anal. Calcd. for C18H20N3OF: (313.37); C, 68.99; H, 6.43; N,
13.41; Found: C, 68.62; H, 6.32; N, 13.55%.
2.4.2.8 N-pivaloyl-N′-ethyl-N″-phenylguanidine (a8)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.1 mL (10 mmol) ethylamine solution,
38
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol) mercury(II) chloride. Yield
1.95 g (79%); compound colorless; m. p. 86-87 ºC; FT-IR (KBr, cm-1): 3425, 3208,
3157, 3060, 2986, 1619, 1575, 1448, 1380, 987, 815; 1H NMR (300 MHz, CDCl3, 25
°C): δ 1.15 (t, 3H, 3J = 7.2 Hz, NCH2CH3), 1.45 (s, 9H, COC(CH3)3), 3.36-3.42 (m,
2H, NCH2CH3), 6.72-6.79 (m, 3H, Ar-H), 7.15-7.21 (m, 2H, Ar-H), 7.89 (s, 1H, NH),
12.20 (s, 1H, NH; 13C NMR (75 MHz, CDCl3, 25 ºC): δ 11.3 (NCH2CH3), 26.9 (3C,
COC(CH3)3), 41.3 (COC(CH3)3), 43.5 (NCH2CH3), 119.3, 122.8 (2C), 129.2 (2C),
142.2 (Aromatic-C), 158.9 (CN3), 179.7 (C=O); Anal. Calcd. for C14H21N3O:
(247.36); C, 67.98; H, 8.56; N, 16.99; Found: C, 67.69; H, 8.59; N, 16.78%.
2.4.2.9 N-pivaloyl-N′-(n-propyl)-N″-phenylguanidine (a9)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 0.8 mL (10 mmol) n-propylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.12 g (81%); compound
colorless; m. p. 75-76 ºC; FT-IR (KBr, cm-1): 3418, 3245, 3137, 3060, 2995, 1632,
1560, 1447, 1373, 937, 745; 1H NMR (300 MHz, CDCl3, 25 °C): δ 0.88 (t, 3H, 3J =
7.2 Hz, NCH2CH2CH3), 1.42 (s, 9H, COC(CH3)3), 1.51 (sex, 2H, 3J = 7.2 Hz,
NCH2CH2CH3), 3.36-3.41 (m, 2H, NCH2CH2CH3), 6.70-6.74 (m, 2H, Ar-H), 6.75-
6.79 (m, 1H, Ar-H), 7.14-7.20 (m, 2H, Ar-H), 8.33 (s, 1H, NH), 12.21 (s, 1H, NH);
13C NMR (75 MHz, CDCl3, 25 °C): δ 12.3 (NCH2CH2CH3), 26.8 (3C, COC(CH3)3),
28.1 (NCH2CH2CH3), 40.0 (COC(CH3)3), 42.6 (NCH2CH2CH3), 118.6, 123.2 (2C),
129.4 (2C), 141.8 (Aromatic-C), 158.7 (CN3), 179.6 (C=O); Anal. Calcd. for
C15H23N3O: (261.36); C, 68.93; H, 8.87; N, 16.08; Found: C, 68.64; H, 8.77; N,
16.27%.
2.4.2.10 N-pivaloyl-N′-(n-butyl)-N″-phenylguanidine (a10)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.0 mL (10 mmol) n-butylamine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.20 g (80%); compound
colorless; m. p. 78-79 ºC; FT-IR (KBr, cm-1): 3437, 3269, 3152, 3062, 2941, 1583,
1530, 1459, 1360, 1178, 985, 848; 1H NMR (300 MHz, CDCl3, 25 °C): δ 0.78 (t, 3H,
3J = 7.2 Hz, NCH2CH2CH2CH3), 1.25 (sex, 2H, 3J = 7.2 Hz, NCH2CH2CH2CH3), 1.43
(s, 9H, COC(CH3)3), 1.45 (quin, 2H, 3J = 7.2 Hz, NCH2CH2CH2CH3), 3.52-3.56 (m,
39
2H, NCH2CH2CH2CH3), 6.72-6.75 (m, 2H, Ar-H), 6.91-7.13 (m, 3H, Ar-H), 7.53 (s,
1H, NH), 12.42 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 11.2
(NCH2CH2CH2CH3), 26.4 (NCH2CH2CH2CH3), 27.2 (3C, COC(CH3)3), 29.4
(NCH2CH2CH2CH3), 40.7 (COC(CH3)3), 46.2 (NCH2CH2CH2CH3), 122.1 (2C),
126.6, 129.9 (2C), 141.2 (Aromatic-C), 158.7 (CN3), 178.3 (C=O); Anal. Calcd. for
C16H25N3O: (275.39); C, 69.78; H, 9.15; N, 15.26; Found: C, 69.57; H, 9.09; N,
15.37%.
2.4.2.11 N-pivaloyl-Nʹ-(iso-propyl)-Nʺ-phenylguanidine (a11)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 0.9 mL (10 mmol) iso-propylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.07 g (79%); compound
colorless; m. p. 66-67 ºC; FT-IR (KBr, cm-1): 3446, 3219, 3127, 3055, 2970, 1661,
1565, 1453, 1370, 845, 765; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.14 (d, 6H, 3J =
6.9 Hz, NCH(CH3)2), 1.46 (s, 9H, COC(CH3)3), 4.32-4.39 (m, 1H, NCH(CH3)2), 6.68-
6.72 (m, 2H, Ar-H), 6.77-6.81 (m, 1H, Ar-H), 7.17-7.22 (m, 2H, Ar-H), 8.12 (s, 1H,
NH), 12.32 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 22.6 (2C,
NCH(CH3)2), 27.3 (3C, COC(CH3)3), 40.3 (COC(CH3)3), 42.7 (NCH(CH3)2), 119.1,
122.9 (2C), 129.5 (2C), 142.3 (Aromatic-C), 159.1 (CN3), 179.4 (C=O); Anal. Calcd.
for C15H23N3O: (261.36); C, 68.93; H, 8.87; N, 16.08; Found: C, 68.57; H, 8.93; N,
15.97%.
2.4.2.12 N-pivaloyl-N′-(sec-butyl)-N″-phenylguanidine (a12)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.1 mL (10 mmol) sec-butylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.20 g (80%); compound
colorless; m. p. 70-71 ºC; FT-IR (KBr, cm-1): 3424, 3278, 3145, 3065, 2974, 1632,
1548, 1455, 1382, 1148, 869, 757; 1H NMR (300 MHz, CDCl3, 25 °C): δ 0.85 (t, 3H,
3J = 7.4 Hz, NCH(CH3)CH2CH3), 1.17 (s, 9H, COC(CH3)3), 1.34-1.56 (m, 5H,
NCH(CH3)CH2CH3), 4.35-4.39 (m, 1H, NCH(CH3)CH2CH3), 6.71-6.74 (m, 1H, Ar-
H), 6.91-6.96 (m, 2H, Ar-H), 7.04-7.08 (m, 1H, Ar-H), 7.11-7.14 (m, 1H, Ar-H), 7.62
(s, 1H, NH), 12.67 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 ºC): δ 12.2
(NCH(CH3)CH2CH3), 26.2 (NCH(CH3)CH2CH3), 26.8 (3C, COC(CH3)3), 30.3
40
(NCH(CH3)CH2CH3), 40.4 (COC(CH3)3), 48.3 (NCH(CH3)CH2CH3), 121.9, 122.4
(2C), 130.7 (2C), 141.8 (Aromatic-C), 158.8 (CN3), 178.2 (C=O); Anal. Calcd. for
C16H25N3O: (275.39); C, 69.78; H, 9.15; N, 15.26; Found: C, 69.61; H, 8.98; N,
15.18%.
2.4.2.13 N-pivaloyl-N′,N′-dipropyl-N″-phenylguanidine (a13)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-N′-
phenylthiourea, 1.38 mL (10 mmol) dipropylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride [5]. Yield 2.34 g (77%); compound
colorless; m. p. 77-78 ºC; FT-IR (KBr, cm-1): 3420, 3130, 3062, 3018, 2987, 1680,
1575, 1352, 1280, 835; 1H NMR (300 MHz, CDCl3, 25 ºC): δ 0.83 (t, 6H, 3J = 6.6 Hz,
N(CH2CH2CH3)2), 1.18 (s, 9H, COC(CH3)3), 1.60 (m, 4H, N(CH2CH2CH3)2), 3.23
(m, 4H, N(CH2CH2CH3)2), 6.98-7.09 (m, 3H, Ar-H), 7.26-7.31 (m, 2H, Ar-H), 11.44
(s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 ºC): δ 11.4 (2C, N(CH2CH2CH3)2),
21.1(2C, N(CH2CH2CH3)2), 28.0 (3C, COC(CH3)3), 41.5 (COC(CH3)3), 50.6 (2C,
N(CH2CH2CH3)2, 122.0 (2C), 124.1, 129.2 (2C), 140.3 (Aromatic-C), 159.7 (CN3),
191.6 (C=O); Anal. Calcd. for C18H29N3O: (303.44); C, 71.25; H, 9.63; N, 13.85;
Found: C, 70.92; H, 9.59; N, 13.87%.
2.4.2.14 N-pivaloyl-N′,N′-dibutyl-N″-phenylguanidine (a14)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.7 mL (10 mmol) dibutylamine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.51 g (76%); compound
colorless; m. p. 85-86 ºC; FT-IR (KBr, cm-1): 3406, 3135, 3052, 3010, 2981, 1690,
1520, 1365, 1120, 780; 1H NMR (300 MHz, CDCl3, 25 °C): δ 0.81 (t, 6H, 3J = 7.2
Hz, N(CH2CH2CH2CH3)2, 1.25 (sex, 4H, 3J = 7.2 Hz, N(CH2CH2CH2CH3)2), 1.42 (s,
9H, COC(CH3)3), 1.44 (quin, 4H, 3J = 7.2 Hz, N(CH2CH2CH2CH3)2), 3.48-3.50 (m,
4H, N(CH2CH2CH2CH3)2), 6.69-6.73 (m, 2H, Ar-H), 6.78-6.81 (m, 1H, Ar-H), 7.10-
7.24 (m, 2H, Ar-H), 12.13 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 12.6
(2C, N(CH2CH2CH2CH3)2), 21.3 (2C, N(CH2CH2CH2CH3)2), 27.1 (3C, COC(CH3)3),
30.7 (2C, N(CH2CH2CH2CH3)2), 40.1 (COC(CH3)3), 49.7 (2C, (2C,
N(CH2CH2CH2CH3)2), 120.1, 122.5 (2C), 129.9 (2C), 142.1, (Aromatic-C), 158.8
41
(CN3), 179.2 (C=O); Anal. Calcd. for C20H33N3O: (331.50); C, 72.46; H, 10.03; N,
12.68; Found: C, 72.37; H, 10.08; N, 12.75%.
2.4.2.15 N-pivaloyl-N′-benzyl-N″-phenylguanidine (a15)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.1 mL (10 mmol) benzylamine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.19 g (71%); compound
colorless; m. p. 87-88 ºC; FT-IR (KBr, cm-1): 3443, 3254,
3149, 3062, 3019, 2949, 1608, 1530, 1458, 1349, 1038, 827; 1H NMR (300 MHz,
C6D6, 25 ºC): δ 1.51 (s, 9H, COC(CH3)3), 4.26 (s, NCH2), 6.77-7.08 (m, 10H, Ar-H),
7.34 (s, 1H, NH), 12.73 (s, 1H, NH); 13C NMR (75 MHz, C6D6, 25 ºC): δ 31.2 (3C,
COC(CH3)3), 38.8 (COC(CH3)3), 58.1 (NCH2), 120.5 (2C), 124.5, 126.7, 128.7 (2C),
128.9 (2C), 129.3 (2C), 137.9, 140.5 (Aromatic-C), 152.9 (CN3), 174.9 (C=O); Anal.
Calcd. for C19H23N3O: (309.40); C, 73.76; H, 7.49; N, 13.58; Found: C, 73.84; H,
7.42; N, 13.45%.
2.4.2.16 N-pivaloyl-N′-(2,5-dichlorophenyl)-N″-phenylguanidine (a16)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.62 g (10 mmol) 2,5-dichloroaniline, 2.
8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.51 g (69%); compound
colorless; m. p. 147-148 ºC; FT-IR (KBr, cm-1): 3408, 3259, 3117, 2972, 2932, 1620,
1534, 1454, 1384, 1178, 854, 748; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.23 (s, 9H,
COC(CH3)3), 6.61.6.63 (m, 1H, Ar-H), 6.78-6.81 (m, 1H, Ar-H), 7.24-7.31 (m, 2H,
Ar-H), 7.57-7.59 (m, 2H, Ar-H), 7.80 (s, 1H, NH), 7.91-7.94 (m, 2H, Ar-H), 12.45 (s,
1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 26.3 (3C, COC(CH3)3), 40.1
(COC(CH3)3), 121.9, 122.5 (2C), 124.3, 124.5, 127.8, 128.1, 128.3, 131.1 (2C), 135.4,
142.1 (Aromatic-C), 159.2 (CN3), 179.1 (C=O); Anal. Calcd. for C18H19N3OCl2:
(364.27); C, 59.35; H, 5.26; N, 11.54; Found: C, 59.12; H, 5.21;N, 11.62%.
2.4.2.17 N-pivaloyl-N′-(2,4-dichlorophenyl)-N″-phenylguanidine (a17)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.62 g (10 mmol) 2,4-dichloroaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
42
mercury(II) chloride. Yield 2.59 g (71%); compound colorless; m. p. 154-155 ºC; FT-
IR (KBr, cm-1): 3413, 3203, 3078, 2962, 1627, 1579, 1542, 1487, 1282, 949, 821; 1H
NMR (300 MHz, C6D6, 25 ºC): δ 0.71 (s, 9H, COC(CH3)3), 6.81-6.84 (m, 3H, Ar-H),
6.87-6.91 (m, 2H, Ar-H), 7.04 (d, 1H, 3J = 9.1 Hz, Ar-H), 7.62 (s, 1H, Ar-H), 9.05 (d,
1H, 3J = 9.1 Hz, Ar-H), 7.24 (s, 1H, NH), 11.25 (s, 1H, NH); 13C NMR (75 MHz,
CDCl3, 25 °C): δ 27.0 (3C, COC(CH3)3), 40.5 (COC(CH3)3), 122.1, 122.3 (2C),
125.1, 127.2, 127.4, 128.7, 130.1 (2C), 135.0, 141.0, 146.3 (Aromatic-C), 159.4
(CN3), 178.6 (C=O); Anal. Calcd. for C18H19N3OCl2: (364.27); C, 59.35; H, 5.26; N,
11.54; Found: C, 59.23; H, 5.31; N, 11.62%.
2.4.2.18 N-pivaloyl-N′-(3,4-dichlorophenyl)-N″-phenylguanidine (a18)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.62 g (10 mmol) 3,4-dichloroaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.55 g (70%); compound
colorless; m. p. 132-133 ºC; FT-IR (KBr, cm-1): 3410,
3268, 3132, 3051, 2952, 1634, 1559, 1448, 1373, 1227,
927, 782; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.19 (s, 9H, COC(CH3)3), 6.57-6.59
(m, 1H, Ar-H), 6.74-6.77 (m, 2H, Ar-H), 6.81-6.85 (m, 2H, Ar-H), 7.34-7.36 (m, 1H,
Ar-H), 7.92-7.95 (m, 2H, Ar-H), 8.79 (s, 1H, NH), 12.37 (s, 1H, NH); 13C NMR (75
MHz, CDCl3, 25 °C): δ 27.1 (3C, COC(CH3)3), 40.2 (COC(CH3)3), 122.7 (2C), 123.6,
124.4, 125.7, 126.2, 126.5, 129.7 (2C), 136.3, 141.1, 146.2 (Aromatic-C), 159.3
(CN3), 178.9 (C=O); Anal. Calcd. for C18H19N3OCl2: (364.27); C, 59.35; H, 5.26; N,
11.54; Found: C, 59.17; H, 5.19; N, 11.32%.
2.4.2.19 N-pivaloyl-N′-(3,5-dichlorophenyl)-N″-phenylguanidine (a19)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.62 g (10 mmol) 3,5-dichloroaniline,
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.59 g (71%); compound
colorless; m. p. 137-138 ºC; FT-IR (KBr, cm-1): 3422,
3236, 3139, 3057, 2978, 1607, 1552, 1547, 1461, 1379,
1288, 1008, 794; 1H NMR (300 MHz, C6D6, 25 ºC): δ 0.69 (s, 9H, COC(CH3)3), 6.86-
6.96 (m, 3H, Ar-H), 7.37 (s, 1H, NH), 7.58 (s, 1H, Ar-H), 7.78-7.80 (m, 2H, Ar-H),
7.87 (s, 2H, Ar-H), 10.64 (s, 1H, NH); 13C NMR (75 MHz, C6D6, 25 °C): δ 26.5 (3C,
43
COC(CH3)3), 40.2 (COC(CH3)3), 121.6, 122.6 (2C), 122.9, 123.7 (2C), 129.2, 130.0
(2C), 135.4 (2C), 146.8 (Aromatic-C), 158.9 (CN3), 178.5 (C=O); Anal. Calcd. for
C18H19N3OCl2: (364.27); C, 59.35; H, 5.26; N, 11.54; Found: C, 59.09; H, 5.29; N,
11.59%.
2.4.2.20 N-pivaloyl-N′-(2,3-dimethylphenyl)-N″-phenylguanidine (a20)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.23 mL (10 mmol) 2,3-dimethylaniline,
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.33 g (72%); compound
colorless; m. p. 104-105 ºC; FT-IR (KBr, cm-1): 3418,
3251, 3149, 3061, 2956, 2932, 1629, 1548, 1458, 1380,
1132, 874; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.21 (s, 9H, COC(CH3)3), 2.16 (s,
3H, Ar-CH3), 2.28 (s, 3H, Ar-CH3), 6.37-6.39 (m, 1H, Ar-H), 6.64-6.67 (m, 2H, Ar-
H), 6.85-6.88 (m, 2H, Ar-H), 7.69-7.75 (m, 3H, Ar-H), 8.32 (s, 1H, NH), 12.36 (s,
1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 21.6 (Ar-CH3), 26.5 (Ar-CH3), 27.3
(3C, COC(CH3)3), 40.1 (COC(CH3)3), 120.4, 122.8 (2C), 123.1, 123.7, 124.7, 126.4,
129.2 (2C), 131.5, 134.5, 141.3 (Aromatic-C), 158.9 (CN3), 178.5 (C=O); Anal.
Calcd. for C20H25N3O: (323.43); C, 74.27; H, 7.79; N, 12.99; Found: C, 74.01; H,
7.83; N, 12.78%.
2.4.2.21 N-pivaloyl-N′-(3-methoxyphenyl)-N″-phenylguanidine (a21)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.2 mL (10 mmol) m-anisidine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.31 g (71%); compound
colorless; m. p. 98-99 ºC; FT-IR (KBr, cm-1): 3432,
3267, 3153, 3048, 2946, 2938, 1638, 1562, 1482, 1371,
1109, 985, 853; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.22 (s, 9H, COC(CH3)3), 3.51
(s, 3H, OCH3), 6.56-6.58 (m, 1H, Ar-H), 6.71-6.75 (m, 2H, Ar-H), 6.94-6.98 (m, 2H,
Ar-H), 7.36-7.38 (m, 2H, Ar-H), 8.31 (s, 1H, NH), 8.35-8.37 (m, 1H, Ar-H), 8.57-
8.59 (m, 1H, Ar-H), 12.71 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 27.7
(3C, COC(CH3)3), 41.2 (COC(CH3)3), 53.8 (OCH3), 117.2, 120.8, 121.7 (2C), 122.2,
123.5, 124.8, 129.7 (2C), 142.3, 147.8, 149.2 (Aromatic-C), 157.9 (CN3), 178.6
44
(C=O); Anal. Calcd. for C19H23N3O2: (325.40); C, 70.13; H, 7.12; N, 12.91; Found: C,
70.24; H, 7.03; N, 12.82%.
2.4.2.22 N-pivaloyl-N′-(tert-butyl)-N″-phenylguanidine (a22)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.1 mL (10 mmol) tert-butylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.18 g (79%); compound
colorless; m. p. 74-75 ºC; FT-IR (KBr, cm-1): 3412,
3240, 3120, 3037, 2987, 1627, 1556, 1456, 1380, 1275, 840; 1H NMR (300 MHz,
C6D6, 25 °C): δ 1.23 (s, 9H, N(CH3)3), 1.55 (s, 9H, COC(CH3)3), 4.59 (s, 1H, NH),
6.79-6.81 (m, 3H, Ar-H), 6.89-6.91 (m, 2H, Ar-H), 12.83 (s, 1H, NH); 13C NMR (75
MHz, C6D6, 25 °C): δ 26.8 (3C, NC(CH3)3), 28.9 (3C, COC(CH3)3), 40.2
(COC(CH3)3), 51.0 (NC(CH3)3), 123.3 (2C), 126.0, 129.9 (2C), 142.6 (Aromatic-C),
158.1 (CN3), 192.3 (C=O); Anal. Calcd. for C16H25N3O: (275.39); C, 69.78; H, 9.15;
N, 15.26; Found: C, 69.39; H, 9.12; N, 15.30%.
2.4.2.23 N-pivaloyl-N′,N′-dimethyl-N″-phenylguanidine (a23)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.26 mL (10 mmol) dimethylamine
solution, 2.8 mL (20 mmol) triethylamine and 2.72 g (10
mmol) mercury(II) chloride. Yield 1.86 g (75%);
compound colorless; m. p. 70-71 ºC; FT-IR (KBr, cm-1): 3447, 3116, 3057, 2992,
1661, 1582, 1371, 978, 812, 705; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.52 (s, 9H,
COC(CH3)3), 3.40 (s, 6H, N(CH3)2), 6.71-6.78 (m, 2H, Ar-H), 6.83-7.21 (m, 3H, Ar-
H), 11.97 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 27.7 (3C, COC(CH3)3),
39.2 (2C, N(CH3)2), 40.5 (COC(CH3)3), 119.4, 122.9 (2C), 129.7 (2C), 140.2
(Aromatic-C), 159.2 (CN3), 179.4 (C=O); Anal. Calcd. for C14H21N3O: (247.34); C,
67.98; H, 8.56; N, 16.99; Found: C, 67.74; H, 8.52; N, 17.08%.
2.4.2.24 N-pivaloyl-N′,N′-diethyl-N″-phenylguanidine (a24)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.1 mL (10 mmol) diethylamine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.12 g (77%); compound
colorless; m. p. 78-79 ºC; FT-IR (KBr, cm-1): 3418, 3142, 3070, 3012, 2985, 1679,
45
1562, 1445, 1367, 956, 735; 1H NMR (300 MHz, C6D6, 25 °C): δ 0.78 (t, 6H, 3J = 7.0
Hz, N(CH2CH3)2), 1.50 (s, 9H, COC(CH3)3), 3.02 (q, 4H, 3J = 7.0 Hz, N(CH2CH3)2),
6.74-6.81 (m, 3H, Ar-H), 6.91-6.96 (m, 2H, Ar-H), 12.21 (s, 1H, NH); 13C NMR (75
MHz, C6D6, 25 °C): δ 12.9 (2C, N(CH2CH3)2), , 28.6 (3C, COC(CH3)3), 42.0
(COC(CH3)3), 43.0 (2C, N(CH2CH3)2), 122.0 (2C), 124.1, 129.5 (2C), 141.1
(Aromatic-C), 160.1 (CN3), 191.9 (C=O); Anal. Calcd. for C16H25N3O: (275.39); C,
69.78; H, 9.15; N, 15.26; Found: C, 69.51; H, 9.21; N, 15.14%.
2.4.2..25 N-pivaloyl-N′-methyl-N′,N″-diphenylguanidine (a25)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.1 mL (10 mmol) N-methylaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.20 g (71%); compound
colorless; m. p. 130-131 ºC; FT-IR (KBr, cm-1): 3421,
3142, 3062, 3035, 2997, 1687, 1516, 1372, 1275, 814; 1H NMR (300 MHz, CDCl3,
25 °C): δ 1.24 (s, 9H, COC(CH3)3), 3.46 (s, 3H, NCH3), 6.80-7.10 (m, 10H, Ar-H),
11.49 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 28.1 (3C, COC(CH3)3), 40.6
(COC(CH3)3), 41.8 (NCH3), 123.4 (2C), 124.4, 125.5, 125.7 (2C), 128.3 (2C), 128.8
(2C), 138.3, 144.3 (Aromatic-C), 159.3 (CN3), 192.2 (C=O); Anal. Calcd. for
C19H23N3O: (309.40); C, 73.76; H, 7.49; N, 13.58; Found: C, 73.71; H, 7.38; N,
13.67%.
2.4.2.26 N-pivaloyl-Nʹ-benzyl-Nʹ-methyl-Nʺ-phenylguanidine (a26)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-N′-
phenylthiourea, 1.2 mL (10 mmol) methylbenzylamine,
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.26 g (70%); compound
colorless; m. p. 132-133 ºC; FT-IR (KBr, cm-1): 3418,
3134, 3075, 3016, 2982, 1665, 1540, 1370, 1185, 851; 1H NMR (300 MHz, CDCl3,
25 °C): δ 1.56 (s, 9H, COC(CH3)3), 3.41 (s, 3H, NCH3), 4.23 (s, 2H, NCH2), 6.61-
6.65 (m, 3H, Ar-H), 6.81-6.84 (m, 2H, Ar-H), 6.93-6.96 (m, 2H, Ar-H), 7.03-7.12 (m,
3H, Ar-H), 12.32 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 27.7 (3C,
COC(CH3)3), 38.5 (NCH3), 40.8 (COC(CH3)3), 52.6 (NCH2), 121.3, 123.2 (2C), 124.0
(2C), 126.2, 127.1 (2C), 129.8 (2C), 134.9, 143.8 (Aromatic-C), 159.1 (CN3), 180.3
46
(C=O); Anal. Calcd. for C20H25N3O: (323.43); C, 74.23; H, 7.79; N, 12.99; Found: C,
74.02; H, 7.83; N, 12.87%.
2.4.2.27 N-pivaloyl-N′-(o-tolyl)-N″-phenylguanidine (a27)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.07 g (10 mmol) o-toluidine, 2.8 mL (20
mmol) triethylamine and 2.72 g (10 mmol) mercury(II)
chloride. Yield 2.10 g (68%); compound colorless; m. p.
81-82 ºC; FT-IR (KBr, cm-1): 3425, 3219, 3161, 3090,
2992, 1647, 1540, 1435, 1360, 1109, 846, 769; 1H NMR (300 MHz, CDCl3, 25 °C): δ
1.29 (s, 9H, COC(CH3)3), 2.34 (s, 3H, Ar-CH3), 6.61-6.65 (m, 2H, Ar-H), 6.82-6.98
(m, 4H, Ar-H), 7.14-7.36 (m, 3H, Ar-H), 7.92 (s, 1H, NH), 11.87 (s, 1H, NH); 13C
NMR (75 MHz, CDCl3, 25 °C): δ 21.3 (Ar-CH3). 27.8 (3C, COC(CH3)3), 40.8
(COC(CH3)3), 119.8, 122.3 (2C), 123.3, 123.2, 124.1, 126.7, 129.6 (2C), 132.7, 135.3,
141.6 (Aromatic-C), 159.2 (CN3), 179.5 (C=O); Anal. Calcd. for C19H23N3O:
(309.40); C, 73.76; H, 7.49; N, 13.58; Found: C, 73.57; H, 7.37; N, 13.62%.
2.4.2.28 N-pivaloyl-N′-cyclohexyl-N″-phenylguanidine (a28)
Quantities used were 2.36 g (10 mmol) N-pivaloyl-Nʹ-
phenylthiourea, 1.2 mL (10 mmol) cyclohexylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.02 g (67%); compound
colorless; m. p. 107-108 ºC; FT-IR (KBr, cm-1): 3427,
3272, 3074, 2931, 1601, 1527, 1460, 1364, 1237, 857; 1H NMR (300 MHz, CDCl3,
25 °C): δ 1.26 (s, 9H, COC(CH3)3), 1.23-2.17 (m, 10H, cyclohexyl-CH2), 4.12-4.15
(m, 1H, cyclohexyl-CH), 6.54-6.56 (m, 1H, Ar-H), 6.71-6.74 (m, 2H, Ar-H), 7.12-
7.16 (m, 2H, Ar-H), 8.31 (s, 1H, NH), 12.57 (s, 1H, NH); 13C NMR (75 MHz, CDCl3,
25 ºC): δ 24.3 (2C, cyclohexyl), 25.8 (cyclohexyl), 27.7 (3C, COC(CH3)3), 34.4 (2C,
cyclohexyl), 52.3 (cyclohexyl), 40.6 (COC(CH3)3), 121.9 (2C), 125.9, 130.1 (2C),
142.3 (Aromatic-C), 159.6 (CN3), 178.7 (C=O); Anal. Calcd. for C18H27N3O:
(301.43); C, 71,72; H, 9.03; N, 13.94; Found: C, 71.51; H, 9.11; N, 13.98%.
47
2.4.3 Synthesis and characterization of N-pivaloyl-N′-(alkyl/aryl)-N″-
pyridylguanidines (b1-b29)
The N-pivaloyl-N′-pyridylthiourea (b) was mixed with the equimolar amount of the
desired amine in DMF and added to two equivalents of triethylamine. One equivalent
of mercury(II) chloride was added to the reaction mixture with continuous stirring
while keeping the temperature below 5 °C using an ice bath. The ice bath was
removed after 30 minutes while stirring was continued for 2-3 hours at room
temperature. The progress of the reaction was monitored by TLC. Dichloromethane
was added to the reaction mixture at the completion of the reaction and the suspension
was filtered through a pad of silica gel to remove the HgS precipitates, formed as
byproduct. The solvents from the filtrate were evaporated under reduced pressure and
the residue was redissolved in CH2Cl2, washed with water (3-4 times) and the organic
phase was dried over anhydrous MgSO4. The solvent was evaporated and the product
was purified by column chromatography. The reaction scheme is given in figure 2.4.
Figure 2.4: Synthesis scheme for the second series of guanidines from N-pivaloyl-Nʹ-
pyridylthiourea
The characterization data for the synthesized compounds in this series is given
along with each compound as follows:
2.4.3.1 N-pivaloyl-N′-phenyl-N″-pyridylguanidine (b1)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-N′-
pyridylthiourea, 1.0 mL (10 mmol) aniline, 2.8 mL (20
mmol) triethylamine and 2.72 g (10 mmol) mercury(II)
chloride. Yield 2.07 g (70%); compound colorless; m. p.
62-63 ºC; FT-IR (KBr, cm-1): 3413, 3245, 3128, 3043, 2988, 1634, 1528, 1453, 1378,
1203, 928, 749; 1H NMR (300 MHz, C6D6, 25 °C): δ 1.14 (s, 9H, COC(CH3)3), 6.38-
6.43 (m, 1H, Ar-H), 6.90-6.96 (m, 1H, Ar-H), 7.03-7.12 (m, 2H, Ar-H), 7.18-7.23 (m,
2H, Ar-H), 7.86-7.88 (m, 1H, Ar-H), 7.97-8.00 (m, 2H, Ar-H), 11.39 (s, 1H, NH),
14.52 (s, 1H, NH); 13C NMR (75 MHz, C6D6, 25 °C): δ 27.2 (3C, COC(CH3)3), 40.6
48
(COC(CH3)3), 117.0, 121.5 (2C), 122.4, 123.5, 129.0 (2C), 138.2, 139.4, 145.2, 147.5
(Aromatic-C), 161.6 (CN3), 180.6 (C=O); Anal. Calcd. for C17H20N4O: (296.37); C,
68.89; H, 6.80; N, 18.90; Found: C, 68.71; H, 6.84; N, 18.79%.
2.4.3.2 N-pivaloyl-N′-(2-chlorophenyl)-N″-pyridylguanidine (b2)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-N′-
pyridylthiourea, 1.1 mL (10 mmol) 2-chloroaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.41 g (73%); compound
colorless; m. p. 78-79 ºC; FT-IR (KBr, cm-1): 3418, 3269,
3157, 3058, 2984, 1638, 1537, 1458, 1386, 1239, 935, 763; 1H NMR (300 MHz,
C6D6, 25 ºC): δ 1.14 (s, 9H, COC(CH3)3), 6.40-6.43 (m, 1H, Ar-H), 6.64-6.68 (m, 1H,
Ar-H), 7.00-7.02 (m, 1H, Ar-H), 7.07-7.13(m, 2H, Ar-H), 7.20 (dd, 1H, 3J = 7.9 Hz,
4J = 1.3 Hz, Ar-H), 7.86 (m, 1H, Ar-H), 9.22 (dd, 1H, 3J = 8.3 Hz, 4J = 1.0 Hz, Ar-H),
11.91 (s, 1H, NH), 14.49 (s, 1H, NH); 13C NMR (75 MHz, C6D6, 25 °C): δ 27.2 (3C,
COC(CH3)3), 40.6 (COC(CH3)3), 117.4, 122.4, 123.6, 123.7, 124.4, 127.2, 129.4,
136.8, 138.3, 145.3, 147.4 (Aromatic-C), 161.2 (CN3), 180.2 (C=O); Anal. Calcd. for
C17H19ClN4O: (330.81); C, 61.72; H, 5.79; N, 16.96; Found: C, 61.49; H, 5.72; N,
16.99%.
2.4.3.3 N-pivaloyl-N′-(3-chlorophenyl)-N″-pyridylguanidine (b3)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-N′-
pyridylthiourea, 1.1 mL (10 mmol) 3-chloroaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.45 g (74%); compound
colorless; m. p. 67-68 ºC; FT-IR (KBr, cm-1): 3427, 3254,
3142, 3052, 2965, 1627, 1555, 1460, 1373, 1202, 834, 757; 1H NMR (300 MHz,
C6D6, 25 ºC): δ 1.12 (s, 9H, COC(CH3)3), 6.37-6.42 (m, 1H, Ar-H), 6.78-6.86 (m, 1H,
Ar-H), 6.89-6.93 (m, 1H, Ar-H), 7.00-7.10 (m, 2H, Ar-H), 7.32-7.36 (m, 1H, Ar-H),
7.83-7.85 (m, 1H, Ar-H), 8.50 (s, 1H, Ar-H), 11.32 (s, 1H, NH), 14.46 (s, 1H, NH);
13C NMR (75 MHz, C6D6, 25 ºC): δ 27.3 (3C, COC(CH3)3), 40.7 (COC(CH3)3),
117.5, 119.2, 121.6, 122.7, 123.5, 130.0, 134.9, 138.5, 140.7, 145.3, 147.2 (Aromatic-
C), 161.3 (CN3), 180.9 (C=O); Anal. Calcd. for C17H19ClN4O: (330.81); C, 61.72; H,
5.79; N, 16.96; Found: C, 61.58; H, 5.83; N, 16.87%.
49
2.4.3.4 N-pivaloyl-N′-(4-chlorophenyl)-N″-pyridylguanidine (b4)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.28 g (10 mmol) 4-chloroaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.38 g (72%); compound
colorless; m. p. 82-83 ºC; FT-IR (KBr, cm-1): 3411, 3259,
3137, 3074, 2962, 1617, 1552, 1445, 1381, 1067, 872; 1H NMR (300 MHz, C6D6, 25
ºC): δ 1.14 (s, 9H, COC(CH3)3), 6.39-6.43 (m, 1H, Ar-H), 6.97-7.02 (m, 1H, Ar-H),
7.07-7.11 (m, 1H, Ar-H), 7.13 (d, 2H, 3J = 8.9 Hz, Ar-H), 7.69 (d, 2H, 3J = 8.9 Hz,
Ar-H), 7.84-7.87 (m, 1H, Ar-H), 11.26 (s, 1H, NH), 14.48 (s, 1H, NH); 13C NMR (75
MHz, C6D6, 25 °C): δ 27.2 (3C, COC(CH3)3), 40.6 (COC(CH3)3), 117.2, 122.4, 122.6
(2C), 123.8, 129.0 (2C), 137.9, 138.3, 145.2, 147.2 (Aromatic-C), 161.3 (CN3), 180.7
(C=O); Anal. Calcd. for C17H19ClN4O: (330.81); C, 61.72; H, 5.79; N, 16.94; Found:
C, 61.63; H, 5.65; N, 17.01%.
2.4.3.5 N-pivaloyl-N′-(2-methoxyphenyl)-N″-pyridylguanidine (b5)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.14 mL (10 mmol) o-anisidine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol),
mercury(II) chloride. Yield 2.48 g (76%); compound
colorless; m. p. 80-81 ºC; FT-IR (KBr, cm-1): 3424, 3247,
3162, 3022, 2964, 1648, 1543, 1467, 1380, 1104, 848, 729; 1H NMR (300 MHz,
C6D6, 25 °C): δ 1.15 (s, 9H, COC(CH3)3), 3.39 (s, 3H, OCH3), 6.38-6.43 (m, 1H, Ar-
H), 6.56 (d, 1H, 3J = 8.1 Hz, Ar-H), 6.91-6.96 (m, 1H, Ar-H), 7.09-7.13 (m, 3H, Ar-
H), 7.87-7.90 (m, 1H, Ar-H), 9.47 (dd, 1H, 3J = 8.1 Hz, 4J = 1.6 Hz, Ar-H), 11.93 (s,
1H, NH), 14.54 (s, 1H, NH); 13C NMR (75 MHz, C6D6, 25 °C): δ 27.3 (3C,
COC(CH3)3), 40.6 (COC(CH3)3), 55.5 (OCH3), 110.3, 116.8, 121.1, 121.9, 122.5,
123.0, 129.5, 138.2, 145.2, 147.6, 149.6 (Aromatic-C), 161.8 (CN3), 179.9 (C=O);
Anal. Calcd. for C18H22N4O2: (326.39); C, 66.24; H, 6.79; N, 17.17; Found: C, 66.01;
H, 6.82; N, 16.96%.
2.4.3.6 N-pivaloyl-Nʹ-( p-tolyl)-Nʺ-pyridylguanidine (b6)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.07 g (10 mmol) p-toluidine, 2.8 mL (20
mmol) triethylamine and 2.72 g (10 mmol) mercury(II)
50
chloride. Yield 2.14 g (69%); compound colorless; m. p. 67-68 ºC; FT-IR (KBr, cm-
1): 3419, 3252, 3148, 3037, 2951, 1627, 1534, 1462, 1379, 1237, 928, 769; 1H NMR
(300 MHz, C6D6, 25 ºC): δ 1.15 (s, 9H, COC(CH3)3), 2.12 (s, 3H, Ar-CH3), 6.39-6.43
(m, 1H, Ar-H), 7.01-7.11 (m, 4H, Ar-H), 7.88-7.92 (m, 3H, Ar-H), 11.36 (s, 1H, NH),
14.53 (s, 1H, NH); 13C NMR (75 MHz, C6D6, 25 °C): δ 20.9 (Ar-CH3), 27.2 (3C,
COC(CH3)3), 40.6 (COC(CH3)3), 116.8, 121.5 (2C), 122.3, 129.6 (2C), 132.8, 137.0,
138.2, 145.2, 147.6 (Aromatic-C), 161.8 (CN3), 180.6 (C=O); Anal. Calcd. for
C18H22N4O: (310.39); C, 69.65; H, 7.14; N, 18.05; Found: C, 69.34; H, 7.11; N,
18.21%.
2.4.3.7 N-pivaloyl-N′-(2-fluorophenyl)-N″-pyridylguanidine (b7)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.0 mL (10 mmol) 2-fluoroaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.20 g (70%); compound
colorless; m. p. 80-81 ºC; FT-IR (KBr, cm-1): 3428, 3243,
3140, 3062, 2957, 1617, 1564, 1454, 1363, 1055, 728; 1H NMR (400 MHz, C6D6, 25
ºC): δ 1.12 (s, 9H, COC(CH3)3), 6.39-6.42 (m, 1H, Ar-H), 6.65-6.70 (m, 1H, Ar-H),
6.83-6.88 (m, 1H, Ar-H), 7.01-7.05 (m, 2H, Ar-H), 7.07-7.12 (m, 1H, Ar-H), 7.85-
7.87 (m, 1H, Ar-H), 9.13-9.17 (m, 1H, Ar-H), 11.79 (s, 1H, NH), 14.47 (s, 1H, NH);
13C NMR (100 MHz, C6D6, 25 ºC): δ 27.2 (3C, COC(CH3)3), 40.6 (COC(CH3)3),
114.7, 117.3, 122.4, 123.2, 123.3, 123.4, 124.3, 124.4, 138.3, 145.3, 147.4 (Aromatic-
C), 161.3 (CN3), 180.5 (C=O); Anal. Calcd. for C17H19N4OF: (314.36); C, 64.95; H,
6.09; N, 17.82; Found: C, 64.77; H, 6.14; N, 17.73%.
2.4.3.8 N-pivaloyl-Nʹ-ethyl-Nʺ-pyridylguanidine (b8)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.1 mL (10 mmol) ethylamine solution,
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.01 g (81%); compound
colorless; m. p. 59-60 ºC; FT-IR (KBr, cm-1): 3432, 3252, 3139, 3052, 2973, 1628,
1547, 1454, 1374, 979, 764; 1H NMR (300 MHz, CDCl3, 25 C): δ 1.14 (s, 9H,
COC(CH3)3), 1.16 (t, 3H, 3J = 7.2 Hz, NCH2CH3), 3.36-3.38 (m, 2H, NCH2CH3),
6.17-6.21 (m, 1H, Ar-H), 6.41-6.46 (m, 1H, Ar-H), 7.14-7.19 (m, 1H, Ar-H), 7.95-
7.98 (m, 1H, Ar-H), 9.34 (s, 1H, NH), 14.58 (s, 1H, NH); 13C NMR (75 MHz, CDCl3,
51
25 ºC): δ 10.9 (NCH2CH3), 27.2 (3C, COC(CH3)3), 40.4 (COC(CH3)3), 43.3
(NCH2CH3), 117.4, 120.9, 136.2, 146.3, 148.7 (Aromatic-C), 160.2 (CN3), 180.5
(C=O); Anal. Calcd. for C13H20N4O: (248.35); C, 62.88; H, 8.12; N, 22.56; Found: C,
62.97; H, 8.08; N, 22.45%.
2,4.3.9 N-pivaloyl-Nʹ-(n-propyl)-Nʺ-pyridylguanidine (b9)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-N′-
pyridylthiourea, 0.8 mL (10 mmol) n-propylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.07 g (79%); compound
colorless; m. p. 61-62 ºC; FT-IR (KBr, cm-1): 3439, 3268, 3074, 2986, 1619, 1534,
1435, 1395, 1238, 958, 857; 1H NMR (300 MHz, C6D6, 25 °C): δ 0.86 (t, 3H, 3J =
7.4, NCH2CH2CH3), 1.22 (s, 9H, COC(CH3)3), 1.41-1.55 (m, 2H, NCH2CH2CH3),
3.37-3.47 (m, 2H, NCH2CH2CH3), 6.48-6.51 (m, 1H, Ar-H), 7.14-7.16 (m, 1H, Ar-H),
7.20-7.25 (m, 1H, Ar-H), 7.96-7.98 (m, 1H, Ar-H), 9.02 (s, 1H, NH), 14.59 (s, 1H,
NH); 13C NMR (75 MHz, C6D6, 25 ºC): δ 11.7 (NCH2CH2CH3), 22.9
(NCH2CH2CH3), 27.3 (3C, COC(CH3)3), 40.5 (COC(CH3)3), 40.5 COC(CH3)3), 42.7
(NCH2CH2CH3), 115.8, 121.7, 138.0, 145.1, 145.9 (Aromatic-C), 162.7 (CN3), 180.3
(C=O); Anal. Calcd. for C14H22N4O: (262.35); C, 64.09; H, 8.45; N, 21.36; Found: C,
63.92; H, 8.40; N, 21.27%.
2.4.3.10 N-pivaloyl-N′-(n-butyl)-N″-pyridylguanidine (b10)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.0 mL (10 mmol) n-butylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.27 g (82%); compound
colorless; m. p. 62-63 ºC; FT-IR (KBr, cm-1): 3441, 3258, 3148, 3054, 2973, 1603,
1527, 1449, 1357, 1217, 938, 792; 1H NMR (300 MHz, CDCl3, 25 °C): δ 0.76 (t, 3H,
3J = 7.2 Hz, NCH2CH2CH2CH3), 1.14 (s, 9H, COC(CH3)3), 1.24 (sex, 2H, 3J = 7.2
Hz, NCH2CH2CH2CH3), 1.41 (quin, 2H, 3J = 7.2 Hz, NCH2CH2CH2CH3), 3.45-3.49
(m, 2H, NCH2CH2CH2CH3), 6.42-6.45 (m, 1H, Ar-H), 6.64-6.68 (m, 1H, Ar-H), 7.12-
7.23 (m, 1H, Ar-H), 7.91-7.93 (m, 1H, Ar-H), 10.01 (s, 1H, NH), 14.53 (s, 1H, NH);
13C NMR (75 MHz, CDCl3, 25 ºC): δ 10.3 (NCH2CH2CH2CH3), 27.2
(NCH2CH2CH2CH3) 27.6 (3C, COC(CH3)3, 29.4 (NCH2CH2CH2CH3), 40.9
(COC(CH3)3), 45.7 NCH2CH2CH2CH3), 119.1, 120.7, 137.2, 144.7, 148.3 (Aromatic-
52
C), 160.1 (CN3), 180.2 (C=O); Anal. Calcd. for C15H24N4O: (276.38); C, 65.19; H,
8.75; N, 20.07; Found: C, 65.02; H, 8.77; N, 20.38%.
2.4.3.11 N-pivaloyl-Nʹ-(iso-propyl)-Nʺ-pyridylguanidine (b11)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 0.9 mL (10 mmol) iso-propylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.10 g (80%); compound
colorless; m. p. 65-66 ºC; FT-IR (KBr, cm-1): 3428, 3239, 3143, 3057, 2964, 1627,
1554, 1483, 1353, 1232, 927, 785; 1H NMR (300 MHz, C6D6, 25 °C): δ 1.15 (d, 6H,
3J = 6.6 Hz, NCH(CH3)2), 1.18 (s, 9H, COC(CH3)3), 4.35-4.53 (m, 1H, NCH(CH3)2),
6.18-6.27 (m, 1H, Ar-H), 6.42-6.45 (m, 1H, Ar-H), 7.12-7.16 (m, 1H, Ar-H), 7.92-
7.95 (m, 1H, Ar-H), 8.99 (s, 1H, NH), 14.57 (s, 1H, NH); 13C NMR (75 MHz, C6D6,
25 °C): δ 22.8 (2C, NCH(CH3)2), 27.3 (3C, COC(CH3)3), 40.5 (COC(CH3)3), 42.4
(NCH(CH3)2), 115.8, 121.7, 138.0, 145.1, 150.3 (Aromatic-C), 162.7 (CN3), 180.4
(C=O); Anal. Calcd. for C14H22N4O: (262.35); C, 64.09; H, 8.45; N, 21.36; Found: C,
63.87; H, 8.47; N, 21.25%.
2.4.3.12 N-pivaloyl-N′-(sec-butyl)-N″-pyridylguanidine (b12)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.1 mL (10 mmol) sec-butylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.16 g (78%); compound
colorless; m. p. 56-57 ºC; FT-IR (KBr, cm-1): 3429, 3258, 3148, 3071, 2964, 1627,
1558, 1461, 1383, 1126, 992, 843, 761; 1H NMR (300 MHz, C6D6, 25 °C): δ 0.88 (t,
3H, 3J = 7.5 Hz, NCH(CH3)CH2CH3), 1.15 (s, 9H, COC(CH3)3), 1.35-1.58 (m, 5H,
NCH(CH3)CH2CH3), 4.37-4.40 (m, 1H, NCH(CH3)CH2CH3), 6.41-6.45 (m, 1H, Ar-
H), 7.08-7.10 (m, 1H, Ar-H), 7.14-7.19 (m, 1H, Ar-H), 7.90-7.92 (m, 1H, Ar-H), 8.98
(s, 1H, NH), 14.56 (s, 1H, NH); 13C NMR (75 MHz, C6D6, 25 °C): δ 10.5
(NCH(CH3)CH2CH3), 27.3 (3C, COC(CH3)3), 28.6 (NCH(CH3)CH2CH3), 29.7
(NCH(CH3)CH2CH3), 40.6 (COC(CH3)3), 47.7 (NCH(CH3)CH2CH3), 115.8, 121.7,
138.0, 145.1, 145.9 (Aromatic-C), 162.7 (CN3), 180.4 (C=O); Anal. Calcd. for
C15H24N4O: (276.38); C, 65.19; H, 8.75; N, 20.27; Found: C, 64.91; H, 8.80; N,
20.19%.
53
2.4.3.13 N-pivaloyl-N′, N′-dipropyl-N″-pyridylguanidine (b13)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.38 mL (10 mmol) dipropylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.28 g (75%); compound
colorless; m. p. 80-81 ºC; FT-IR (KBr, cm-1): 3439, 3142, 3057, 2972, 1658, 1549,
1481, 1361, 1237, 976, 775; 1H NMR (300 MHz, C6D6, 25 °C): δ 0.86 (t, 6H, 3J = 7.3
Hz, N(CH2CH2CH3)2), 1.15 (s, 9H, COC(CH3)3), 1.61 (sex, 4H, 3J = 7.3,
N(CH2CH2CH3)2), 3.36-3.38 (m, 4H, N(CH2CH2CH3)2), 6.40-6.44 (m, 1H, Ar-H),
6.96-6.98 (m, 1H, Ar-H), 7.07-7.12 (m, 1H, Ar-H), 8.04-8.05 (m, 1H, Ar-H), 12.27 (s,
1H, NH); 13C NMR (75 MHz, C6D6, 25 °C): δ 11.6 (2C, N(CH2CH2CH3)2), 21.6 (2C,
N(CH2CH2CH3)2), 27.4 (3C, COC(CH3)3), 40.3 (COC(CH3)3), 50.6 (2C,
N(CH2CH2CH3)2), 116.4, 121.2, 137.8, 146.2, 150.4 (Aromatic-C), 161.8 (CN3),
176.7 (C=O); Anal. Calcd. for C17H28N4O: (304.43); C, 67.07; H, 9.27; N, 18.40;
Found: C, 66.89; H, 9.18; N, 18.37%.
2.4.3.14 N-pivaloyl-N′,N′-dibutyl-N″-pyridylguanidine (b14)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.7 mL (10 mmol) dibutylamine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.39 g (72%); compound
colorless; m. p. 70-71 ºC; FT-IR (KBr, cm-1): 3425, 3141,
3045, 2965, 1657, 1563, 1465, 1373, 1119, 928, 798; 1H NMR (300 MHz, CDCl3, 25
ºC): δ 0.75 (t, 6H, 3J = 7.3 Hz, N(CH2CH2CH2CH3)2), 1.14 (s, 9H, COC(CH3)3), 1.23
(sex, 4H, 3J = 7.3 Hz, N(CH2CH2CH2CH3)2), 1.41 (quin, 4H, 3J = 7.3 Hz,
N(CH2CH2CH2CH3)2), 3.44-3.47 (m, 4H, N(CH2CH2CH2CH3)2), 6.19-6.22 (m, 1H,
Ar-H), 6.43-6.47 (m, 1H, Ar-H), 7.15-7.20 (m, 1H, Ar-H), 7..91-7.96 (m, 1H, Ar-H),
14.51 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 12.7 (2C,
N(CH2CH2CH2CH3)2), 20.8 (2C, N(CH2CH2CH2CH3)2), 26.9 (3C, COC(CH3)3), 31.6
(2C, N(CH2CH2CH2CH3)2), 40.1 (COC(CH3)3), 49.2 (2C, N(CH2CH2CH2CH3)2),
116.9, 120.8, 136.4, 146.5, 148.1 (Aromatic-C), 160.1 (CN3), 179.4 (C=O); Anal.
Calcd. for C19H32N4O: (332.48); C, 68.64; H, 9.70; N, 16.85; Found: C, 68.41; H,
9.75; N, 16.72%.
54
2.4.3.15 N-pivaloyl-Nʹ-benzyl-Nʺ-pyridylguanidine (b15)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.1 mL (10 mmol) benzylamine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.20 g (71%); compound
colorless; m. p. 72-73 ºC; FT-IR (KBr, cm-1): 3439,
3262, 3138, 3041, 2955, 1616, 1556, 1465, 1379, 1208, 1073, 784; 1H NMR (300
MHz, CDCl3, 25 °C): δ 1.13 (s, 9H, COC(CH3)3), 4.27 (s, 2H, NCH2), 6.12-6.22 (m,
1H, Ar-H), 6.40-6.44 (m, 1H, Ar-H), 6.66-6.75 (m, 3H, Ar-H), 7.09-7.32 (m, 2H, Ar-
H), 7.90-7.98 (m, 2H, Ar-H), 10.79 (s, 1H, NH), 14.48 (s, 1H, NH); 13C NMR (75
MHz, CDCl3, 25 °C): δ 27.5 (3C, COC(CH3)3), 40.8 (COC(CH3)3), 52.1 (NCH2),
119.3, 120.7, 122.3 (2C), 123.2, 128.5 (2C), 131.6, 131.8, 135.9, 147.7 (Aromatic-C),
162.4 (CN3), 179.5 (C=O); Anal. Calcd. for C18H22N4O: (310.39); C, 69.65; H, 7.14;
N, 18.05; Found: C, 69.29; H, 7.19; N, 18.14%.
2.4.3.16 N-pivaloyl-Nʹ-(2,5-dichlorophenyl)-Nʺ-pyridylguanidine (b16)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-N′-
pyridylthiourea, 1.62 g (10 mmol) 2,5-dichloroaniline,
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.56 g (70%); compound
colorless; m. p. 81-82 ºC; FT-IR (KBr, cm-1): 3425, 3254,
3152, 2984, 2943, 1615, 1562, 1468, 1373, 1127, 948, 829; 1H NMR (300 MHz,
CDCl3, 25 °C): δ 1.16 (s, 9H, COC(CH3)3), 6.51-6.54 (m, 1H, Ar-H), 6.82-6.84 (m,
1H, Ar-H), 7.21-7.28 (m, 2H, Ar-H), 7.43-7.52 (m, 2H, Ar-H), 7.76-7.79 (m, 1H, Ar-
H), 11.63 (s, 1H. NH), 14.47 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 27.1
(3C, COC(CH3)3), 40.6 (COC(CH3)3), 119.7, 120.3, 121.7, 122,1, 122.9, 125.5, 135.6,
135.9, 136.8, 145.3, 147.4 (Aromatic-C), 161.3 (CN3), 180.4 (C=O); Anal. Calcd. for
C17H18Cl2N4O: (365.26); C, 55.90; H, 4.97; N, 15.34; Found: C, 55.76; H, 4.88; N,
15.43%.
2.4.3.17 N-pivaloyl-N′-(2,4-dichlorophenyl)-N″-pyridylguanidine (b17)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.62 g (10 mmol) 2,4-dichloroaniline,
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.52 g (69%); compound
55
colorless; m. p. 84-85 ºC; FT-IR (KBr, cm-1): 3448, 3239, 3148, 3038, 2957, 1634,
1567, 1481, 1353, 1217, 953, 846, 774; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.18 (s,
9H, COC(CH3)3), 6.40-6.43 (m, 1H, Ar-H), 6.73-6.77 (m, 2H, Ar-H), 7.46-7.52 (m,
3H, Ar-H), 7.81-7.83 (m, 1H, Ar-H), 11.51 (s, 1H, NH), 14.39 (s, 1H, NH); 13C NMR
(75 MHz, CDCl3, 25 °C): δ 27.2 (3C, COC(CH3)3), 40.3 (COC(CH3)3), 119.3, 120.2,
121.1, 122.8, 124.6, 124.9, 136.6, 137.1, 137.8, 146.2, 148.7 (Aromatic-C), 162.2
(CN3), 180.5 (C=O); Anal. Calcd. for C17H18Cl2N4O: (365.26); C, 55.90; H, 4.97; N,
15.34; Found: C, 55.72; H, 5.02; N, 15.23%.
2.4.3.18 N-pivaloyl-Nʹ-(3,4-dichlorophenyl)-N″-pyridylguanidine (b18)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.62 g (10 mmol) 3,4-dichloroaniline,
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.63 g 72%); compound
colorless; m. p. 90-91 ºC; FT-IR (KBr, cm-1): 3417, 3259,
3134, 3065, 2947, 1621, 1563, 1457, 1382, 1218, 952, 824; 1H NMR (300 MHz,
CDCl3, 25 °C): δ 1.16 (s, 9H, COC(CH3)3), 6.47-6.49 (m, 1H, Ar-H), 6.82-6.85 (m,
1H, Ar-H), 7.62-7.66 (m, 2H, Ar-H), 7.75-7.78 (m, 2H, Ar-H), 8.02-8.06 (m, 1H, Ar-
H), 11.74 (s, 1H, NH), 14.56 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 27.0
(3C, COC(CH3)3), 40.2 (COC(CH3)3), 118.7, 120.1, 120.8, 122.6, 123.7, 124.1, 124.7,
135.4, 137.1, 145.3, 147.9 (Aromatic-C), 161.8 (CN3), 181.1 (C=O); Anal. Calcd. for
C17H18Cl2N4O: (365.26); C, 55.90; H, 4.97; N, 15.34; Found: C, 56.07; H, 4.88; N,
15.28%.
2.4.3.19 N-pivaloyl-N′-(3,5-dichlorophenyl)-N″-pyridylguanidine (b19)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.62 g (10 mmol) 3,5-dichloroaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.70 g (74%); compound
colorless; m. p. 78-79 ºC; FT-IR (KBr, cm-1): 3417, 3243,
3133, 3052, 2967, 1614, 1554, 1456, 1374, 1243, 1029, 828,772; 1H NMR (300 MHz,
CDCl3, 25 °C): δ 1.15 (s, 9H, COC(CH3)3), 6.51-6.54 (m, 1H, Ar-H), 6.72-6.74 (m,
1H, Ar-H), 7.61 (s, 1H, Ar-H), 7.78-7.83 (m, 2H, Ar-H), 8.36 (s, 2H, Ar-H), 11.81 (s,
1H, NH), 14.59 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 ºC): δ 27.2 (3C,
COC(CH3)3), 40.5 (COC(CH3)3), 119.1, 121.6, 122.1 (2C), 123.4, 134.7, 135.2 (2C),
56
137.3, 145.2, 148.1 (Aromatic-C), 161.7 (CN3), 180.9 (C=O); Anal. Calcd. for
C17H18Cl2N4O: (365.26); C, 55.90; H, 4.97; N, 15.34; Found: C, 55.83; H, 4.90; N,
15.18%.
2.4.3.20 N-pivaloyl-N′-(2,3-dimethylphenyl)-N″-pyridylguanidine (b20)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.23 mL (10 mmol) 2,3-dimethylaniline,
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.50 g (77%); compound
colorless; m. p. 70-71 ºC; FT-IR (KBr, cm-1): 3414, 3247,
3138, 3056, 2943, 1618, 1534, 1465, 1371, 1213, 938, 835; 1H NMR (300 MHz,
CDCl3, 25 °C): δ 1.14 (s, 9H, COC(CH3)3), 2.14 (s, 3H, Ar-CH3), 2.25 (s, 3H, Ar-
CH3), 6.33-6.36 (m, 1H, Ar-H), 6.52-6.56 (m, 2H, Ar-H), 6.94-6.96 (m, 1H, Ar-H),
7.41-7.82 (m, 3H, Ar-H), 11.82 (s, 1H, NH), 14.41 (s, 1H, NH); 13C NMR (75 MHz,
CDCl3, 25 °C): δ 20.5 (Ar-CH3), 26.3 (Ar-CH3), 27.4 (3C, COC(CH3)3), 40.4
(COC(CH3)3), 118.2, 120.7, 122.3, 124.5, 125.4, 126.1, 130.7, 131.2, 137.4, 145.1,
147.3 (Aromatic-C), 161.5 (CN3), 180.5 (C=O); Anal. Calcd. for C19H24N4O:
(324.42); C, 70.34; H, 7.46; N, 17.27; Found: C, 70.09; H, 7.39; N, 17.32%.
2.4.3.21 N-pivaloyl-N′-(3-methoxyphenyl)-N″-pyridylguanidine (b21)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.2 mL (10 mmol) m-anisidine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.45 g (75%); compound
colorless; m. p. 85-86 ºC; FT-IR (KBr, cm-1): 3425, 3256,
3148, 3053, 2942, 1629, 1546, 1471, 1384, 1132, 1084, 938, 793; 1H NMR (300
MHz, CDCl3, 25 °C): δ 1.16 (s, 9H, COC(CH3)3), 3.40 (s, 3H, OCH3), 6.39-6.42 (m,
1H, Ar-H), 7.10-7.15 (m, 1H, 1H, Ar-H), 7.39-7.43 (m, 3H, Ar-H), 8.24-8.27 (m, 2H,
Ar-H), 9.35-9.38 (m, 1H, Ar-H), 11.90 (s, 1H, NH), 14.49 (s, 1H, NH); 13C NMR (75
MHz, CDCl3, 25 ºC): δ 27.1 (3C, COC(CH3)3), 40.7 (COC(CH3)3), 55.3 (OCH3),
118.7, 120.5, 121.8, 122.4, 123.8, 125.1, 125.4, 137.7, 145.5, 147.7, 149.3 (Aromatic-
C), 160.8 (CN3), 180.7 (C=O); Anal. Calcd. for C18H22N4O2: (326.39); C, 66.24; H,
6.79; N, 17.17; Found: C, 65.97; H, 6.83; N, 17.08%.
57
2.4.3.22 N-pivaloyl-Nʹ-(tert-butyl)-Nʺ-pyridylguanidine (b22)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.1 mL (10 mmol) tert-butylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.24 g (81%); compound
colorless; m. p. 56-57 ºC; FT-IR (KBr, cm-1): 3423, 3254, 3133, 3042, 2956, 1629,
1548, 1445, 1368, 1207, 924, 856; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.14 (s, 9H,
COC(CH3)3), 1.26 (s, 9H, NC(CH3)3), 6.26-6.32 (m, 1H, Ar-H), 6.58-6.61 (m, 1H,
Ar-H), 7.21-7.34 (m, 1H, Ar-H), 7.90-7.93 (m, 1H, Ar-H), 10.39 (s, 1H, NH), 14.43
(s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 26.4 (3C, NC(CH3)3), 27.7 (3C,
COC(CH3)3), 40.8 (COC(CH3)3), 50.8 (NC(CH3)3), 117.3, 121.4, 129.3, 143.5, 147.8
(Aromatic-C), 161.3 (CN3), 179.9 (C=O); Anal. Calcd. for C15H24N4O: (276.38); C,
65.19; H, 8.75; N, 20.27; Found: C, 65.32; H, 8.66; N, 20.15%.
2.4.3.23 N-pivaloyl-Nʹ,Nʹ-dimethyl-Nʺ-pyridylguanidine (b23)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.26 mL (10 mmol) dimethylamine
solution, 2.8 mL (20 mmol) triethylamine and 2.72 g (10
mmol) mercury(II) chloride. Yield 1.91 g (77%);
compound colorless; m. p. 72-73 ºC; FT-IR (KBr, cm-1): 3423, 3131, 3061, 2987,
1668, 1575, 1459, 1374, 976, 843, 729; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.13 (s,
9H, COC(CH3)3), 3.04 (s, 3H, N(CH3)2), 6.19-6.22 (m, 1H, Ar-H), 6.36-6.38 (m, 1H,
Ar-H), 7.01-7.05 (m, 1H, Ar-H), 7.83-7.88 (m, 1H, Ar-H), 14.52 (s, 1H, NH); 13C
NMR (75 MHz, CDCl3, 25 °C): δ 27.2 (3C, COC(CH3)3), 38.8 (2C, N(CH3)2), 40.4
(COC(CH3)3), 117.8, 121.7, 137.6, 146.3, 148.5 (Aromatic-C), 161.6 (CN3), 180.1
(C=O); Anal. Calcd. for C13H20N4O: (248.32); C, 62.88; H, 8.12; N, 22.56; Found: C,
62.53; H, 8.20; N, 22.37%.
2.4.3.24 N-pivaloyl-Nʹ,Nʹ-diethyl-Nʺ-pyridylguanidine (b24)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-N′-
pyridylthiourea, 1.1 mL (10 mmol) diethylamine, 2.8 mL
(20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.05 g (74%); compound
colorless; m. p. 75-76 ºC; FT-IR (KBr, cm-1): 3427, 3136, 3063, 3026, 2975, 1658,
1567, 1456, 1363, 1137, 942, 751; 1H NMR (300 MHz, CDCl3, 25 °C): δ 1.15 (s, 9H,
58
COC(CH3)3), 1.17 (t, 6H, 3J = 7.5 Hz, N(CH2CH3)2), 3.36 (m, 4H, N(CH2CH3)2),
6.18-6.20 (m, 1H, Ar-H), 6.42-6.45 (m, 1H, Ar-H), 7.13-7.21 (m, 1H, Ar-H), 7.94-
7.97 (m, 1H, Ar-H), 14.53 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 13.4
(2C, N(CH2CH3)2), 27.0 (3C, COC(CH3)3), 40.3 (COC(CH3)3), 45.7 (2C,
N(CH2CH3)2), 118.2, 121.4, 135.8, 145.8, 148.7 (Aromatic-C), 161.2 (CN3), 179.8
(C=O); Anal. Calcd. for C15H24N4O: (276.38); C, 65.19; H, 8.75; N, 20.27; Found: C,
65.31; H, 8.82; N, 20.08%.
2.4.3.25 N-pivaloyl-N′-methyl-N′-phenyl-N″-pyridylguanidine (b25)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.1 mL (10 mmol) N-methylaniline, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.17 g (70%); compound
colorless; m. p. 81-82 ºC; FT-IR (KBr, cm-1): 3427, 3134,
3056, 3052, 2978, 1652, 1534, 1461, 1367, 1264, 925, 832; 1H NMR (300 MHz,
CDCl3, 25 °C): δ 1.14 (s, 9H, COC(CH3)3), 3.06 (s, 3H, NCH3), 6.37-6.39 (m, 1H,
Ar-H), 6.88-6.92 (m, 1H, Ar-H), 7.10-7.12 (m, 2H, Ar-H), 7.16-7.25 (m, 2H, Ar-H),
7.86-7.91 (m, 1H, Ar-H), 7.96-8.01 (m, 2H, Ar-H), 14.38 (s, 1H, NH); 13C NMR (75
MHz, CDCl3, 25 °C): δ 27.6 (3C, COC(CH3)3), 37.4 (NCH3), 40.7 (COC(CH3)3),
119.4, 120.3, 121.3 (2C), 122.8, 123.9, 127.9 (2C), 136.2, 146.1, 148.2 (Aromatic-C),
161.2 (CN3), 180.9 (C=O); Anal. Calcd. for C18H22N4O: (310.39); C, 69.65; H, 7.14;
N, 18.05; Found: C, 69.39; H, 7.19; N, 18.27%.
2.4.3.26 N-pivaloyl-N′-benzyl-N′-methyl-N″-pyridylguanidine (b26)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.2 mL (10 mmol) methylbenzylamine,
2.8 mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.37 g (73%); compound
colorless; m. p. 77-78 ºC; FT-IR (KBr, cm-1): 3424,
3146, 3068, 3028, 2978, 1659, 1536, 1445, 1374, 1176, 938, 843; 1H NMR (300
MHz, CDCl3, 25 °C): δ 1.13 (s, 9H, COC(CH3)3), 3.01 (s, 3H, NCH3), 4.25 (s, 2H,
NCH2), 6.17-6.20 (m, 1H, Ar-H), 6.32-6.37 (m, 3H, Ar-H), 6.42-6.54 (m, 2H, Ar-H),
7.17-7.57 (m, 2H, Ar-H), 7.93-7.97 (m, 1H, Ar-H), 14.41 (s, 1H, NH); 13C NMR (75
MHz, CDCl3, 25 °C): δ 27.4 (3C, COC(CH3)3), 38.9 (NCH3), 40.2 (COC(CH3)3), 53.4
(NCH2), 118.3, 120.5, 121.7 (2C), 123.7, 124.2, 128.2 (2C), 135.5, 145.4, 147.7
59
(Aromatic-C), 161.4 (CN3), 180.3 (C=O); Anal. Calcd. for C19H24N4O: (324.42); C,
70.34; H, 7.46; N, 17.27; Found: C, 70.06; H, 7.57; N, 17.08%.
2.4.3.27 N-pivaloyl-Nʹ-(o-tolyl)-Nʺ-pyridylguanidine (b27)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.07 g (10 mmol) o-toluidine, 2.8 mL (20
mmol) triethylamine and 2.72 g (10 mmol) mercury(II)
chloride. Yield 2.39 g (77%); compound colorless; m. p.
71-72 ºC; FT-IR (KBr, cm-1): 3422, 3232, 3159, 3078,
2973, 1636, 1553, 1447, 1366, 1135, 972, 838, 773; 1H NMR (300 MHz, CDCl3, 25
C): δ 1.13 (s, 9H, COC(CH3)3), 2.23 (s, 3H, Ar-CH3), 6.28-6.32 (m, 1H, Ar-H), 6.46-
6.51 (m, 2H, Ar-H), 7.02-7.46 (m, 3H, Ar-H), 7.87-7.95 (m, 2H, Ar-H), 11.22 (s, 1H,
NH), 14.48 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 21.2 (Ar-CH3), 27.4
(3C, COC(CH3)3), 40.8 (COC(CH3)3), 118.7, 120.5, 121.4, 122.7, 123.4, 123.8, 132.2,
135.8, 145.6, 145.8, 147.9 (Aromatic-C), 160.5 (CN3), 180.9 (C=O); Anal. Calcd. for
C18H22N4O: (310.39); C, 69.65; H, 7.14; N, 18.05; Found: C, 69.57; H, 7.21; N,
17.95%.
2.4.3.28 N-pivaloyl-Nʹ-cyclohexyl-Nʺ-pyridylguanidine (b28)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 1.2 mL (10 mmol) cyclohexylamine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.12 g (70%); compound
colorless; m. p. 103-104 ºC; FT-IR (KBr, cm-1): 3422,
3271, 3127, 3066, 2935, 1614, 1536, 1457, 1376, 1225, 938, 834; 1H NMR (300
MHz, CDCl3, 25 °C): δ 1.15 (s, 9H, COC(CH3)3), 1.21-2.13 (m, 10H, cyclohexyl-
CH2), 4.09-4.17 (m, 1H, cyclohexyl-CH), 6.23-6.28 (m, 1H, Ar-H), 6.44-6.47 (m, 1H,
Ar-H), 7.10-7.22 (m, 1H, Ar-H), 7.92-7.95 (m, 1H, Ar-H), 9.47 (s, 1H, NH), 14.50 (s,
1H, NH); 13C NMR (75 MHz, CDCl3, 25 °C): δ 24.7 (2C, cyclohexyl), 25.6
(cyclohexyl), 27.7 (3C, COC(CH3)3), 33.7 (2C, cyclohexyl), 51.6 (cyclohexyl), 40.8
(COC(CH3)3), 119.7, 123.3, 137.7, 145.2, 147.3 (Aromatic-C), 160.5 (CN3), 180.1
(C=O); Anal. Calcd. for C17H26N4O: (302.41); C, 67.52; H, 8.67; N, 18.53; Found: C,
67.61; H, 8.62; N, 18.44%.
60
2.4.3.29 N-pivaloyl-Nʹ,Nʺ-bipyridylguanidine (b29)
Quantities used were 2.37 g (10 mmol) N-pivaloyl-Nʹ-
pyridylthiourea, 0.94 g (10 mmol) 2-aminopyridine, 2.8
mL (20 mmol) triethylamine and 2.72 g (10 mmol)
mercury(II) chloride. Yield 2.26 g (76%); compound
colorless; m. p. 90-91 ºC; FT-IR (KBr, cm-1): 3423, 3263,
3069, 2943, 1618, 1539, 1448, 1371, 1172, 937, 861; 1H NMR (300 MHz, C6D6, 25
°C): δ 1.10 (s, 9H, COC(CH3)3), 6.40-6.44 (m, 1H, Ar-H), 6.52-6.56 (m, 1H, Ar-H),
7.02-7.12 (m, 2H, Ar-H), 7.31-7.37 (m, 1H, Ar-H), 7.84-7.86 (m. 1H, Ar-H), 8.26-
8.28 (m, 1H, Ar-H), 8.96 (d, 1H, 3J = 8.4 Hz, Ar-H), 12.08 (s, 1H, NH), 14.36 (s, 1H,
NH); 13C NMR (75 MHz, C6D6, 25 ºC): δ 27.1 (3C, COC(CH3)3), 40.7 (COC(CH3)3),
115.3, 117.4, 118.8, 122.3, 137.4, 138.3, 145.3, 147.0, 148.7, 152.9 (Aromatic-C),
161.3 (CN3), 180.0 (C=O); Anal. Calcd. for C16H19N5O: (297.35); C, 64.63; H, 6.44;
N, 23.55; Found: C, 64.31; H, 6.37; N, 23.42%.
2.5 Synthesis and characterization of Cu(II) complexes of
guanidines
2.5.1 General synthetic route for Cu(II) complexes of guanidines
The guanidinatocopper(II) complexes were synthesized from N-pivaloyl-Nʹ-
(alkyl/aryl)-Nʺ-(phenyl/pyridyl) polysubstituted guanidines. The reaction scheme is
given in figure 2.5.
R1 = Phenyl (a1-a28) & Pyridyl (b1-b29)
R2 = Alkyl/aryl group
Figure 2.5: General scheme for the synthesis of guanidinatocopper(II) complexes.
Different guanidines (a1-a28 & b1-b29) were treated with copper(II)
acetate/chloride in methanol/ethanol. The products, guanidinato Cu(II) complexes
61
precipitated which were filtered and washed with methanol/ethanol. The complexes
were purified by recrystallization in dichloromethane. The synthesized complexes
were characterized by elemental analysis, IR spectroscopy, single crystal XRD and
magnetic susceptibility measurements.
2.5.2 Synthesis and characterization of Bis(N-pivaloyl-N΄-(alkyl/aryl)-N˝-
phenylguanidinato)copper(II) complexes (A1-A28)
One equivalent of methanolic solution of copper(II) acetate was mixed with two
equivalent of a methanolic solution of N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-phenylguanidine
(a1-a28) with constant stirring at room temperature. The reaction mixture was stirred
for 3-4 hours at room temperature. The Bis(N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-
phenylguanidinato)copper(II) complexes (A1-A28) were formed as precipitate which
were filtered and washed with methanol. The complexes were further purified by
recrystallization in dichloromethane. The reaction scheme is given in figure 2.6.
Figure 2.6: Synthesis scheme for bis(N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-phenylguani-
dinato)copper(II) complexes.
2.5.2.1 Bis(N-pivaloyl-N′,N″-diphenylguanidinato)copper(II) (A1)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.48 g
(5.0 mmol) N-pivaloyl-Nʹ,Nʺ-diphenylguanidine (1a). Yield 1.32 g (81%); blue solid;
m. p. 170-171 °C; FT-IR (KBr, cm-1): 3427, 3108, 3042, 2983, 1650, 1530, 1368,
1225, 702, 534, 429; Anal. Calcd. for CuC36H40N6O2: (652.29); Cu, 9.74; C, 66.29; H,
6.18; N, 12.88; Found: Cu, 9.51; C, 65.98; H, 6.01; N, 12.82%; µ eff. 1.61 BM.
62
2.5.2.2 Bis(N-pivaloyl-N′-(2-chlorophenyl)-N″-phenylguanidinato)copper(II)
(A2)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.65 g
(5.0 mmol) N-pivaloyl-Nʹ-(2-chlorophenyl)-Nʺ-phenylguanidine (2a). Yield 1.39 g
(77%); blue solid; m. p. 181-182 °C; FT-IR (KBr, cm-1): 3408, 3127, 3056, 2985,
1594, 1463, 1380, 1154, 972, 759, 532, 439; Anal. Calcd. for CuC36H38N6O2Cl2:
(721.18); Cu, 8.81; C, 59.96; H, 5.31; N, 11.65; Found: Cu, 8.58; C, 59.58; H, 5.24;
N, 11.36%; µ eff. 1.58 BM.
2.5.2.3 Bis(N-pivaloyl-N′-(3-chlorophenyl)-N″-phenylguanidinato)copper(II)
(A3)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.65 g
(5.0 mmol) N-pivaloyl-Nʹ-(3-chlorophenyl)-Nʺ-phenylguanidine (3a). Yield 1.42 g
(79%); blue solid; m. p. 178-179 °C; FT-IR (KBr, cm-1): 3394, 2954, 2926, 2864,
1590, 1560, 1511, 1457, 1419, 1352, 1248, 945, 698, 542, 444; Anal. Calcd. for
CuC36H38N6O2Cl2: (721.18); Cu, 8.81; C, 59.96; H, 5.31; N, 11.65; Found: Cu, 9.01;
C, 59.52; H, 5.22; N, 11.37%. µ eff. 1.54 BM.
2.5.2.4 Bis(N-pivaloyl-N′-(4-chlorophenyl)-N″-phenylguanidinato)copper(II)
(A4)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.65 g
(5.0 mmol) N-pivaloyl-Nʹ-(4-chlorophenyl)-Nʺ-phenylguanidine (a4). Yield 1.32 g
(73%); blue solid; m. p. 185-186 ºC; FT-IR (KBr, cm-1): 3384, 3134, 3057, 2981,
1597, 1552, 1461, 1368, 846, 538, 451; Anal. Calcd. for CuC36H38N6O2Cl2: (721.18);
Cu, 8.81; C, 59.96; H, 5.31; N, 11.65; Found: Cu, 8.71; C, 59.54; H, 5.09; N, 11.31%;
µ eff. 1.48 BM.
2.5.2.5 Bis(N-pivaloyl-N′-(2-methoxyphenyl)-N″-phenylguanidinato)copper(II)
(A5)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.63 g
(5.0 mmol) N-pivaloyl-Nʹ-(2-methoxyphenyl)-Nʺ-phenylguanidine (a5). Yield 1.42 g
(80%); blue solid; m. p. 171-172 °C; FT-IR (KBr, cm-1): 3362, 3056, 2962, 2945,
1556, 1483, 1422, 1347, 950, 752, 548, 438; Anal. Calcd. for CuC38H44N6O4:
(712.34); Cu, 8.92; C, 64.07; H, 6.23; N, 11.80; Found: Cu, 8.61; C, 63.79; H, 6.31;
N, 11.72%; µ eff. 1.64 BM.
63
2.5.2.6 Bis(N-pivaloyl-N′-(p-tolyl)-N″-phenylguanidinato)cpper(II) (A6)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.55 g
(5.0 mmol) N-pivaloyl-Nʹ-(p-tolyl)-Nʺ-phenylguanidine (a6). Yield 1.33 g (78%);
blue solid; m. p. 189-190 °C; FT-IR (KBr, cm-1): 3397, 3025, 2953, 2925, 1595, 1561,
1494, 1351, 947, 752, 691, 559, 494; Anal. Calcd. for CuC38H44N6O2: (680.34); Cu,
9.34; C, 67.08; H, 6.52; N, 12.35; Found: Cu, 9.02; C, 67.12; H, 6.57; N, 12.61%; µ
eff. 1.72 BM.
2.5.2.7 Bis(N-pivaloyl-N′-(2-fluorophenyl)-N″-phenylguanidinato)copper(II) (A7)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.56 g
(5.0 mmol) N-pivaloyl-Nʹ-(2-fluorophenyl)-Nʺ-phenylguanidine (a7). Yield 1.31 g
(76%); light blue solid; m. p. 183-184 ºC; FT-IR (KBr, cm-1): 3391, 3119, 3075,
2980, 1602, 1552, 1457, 1369, 936, 762, 530, 437; Anal. Calcd. for CuC36H38N6O2F2:
(688.27); Cu, 9.23; C, 62.82; H, 5.56; N, 21.21; Found: Cu, 8.97; C, 62.61; H, 5.42;
N, 21.09%; µ eff. 1.68 BM.
2.5.2.8 Bis(N-pivaloyl-N′-ethyl-N″-phenylguanidinato)copper(II) (A8)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.24 g
(5.0 mmol) N-pivaloyl-Nʹ-ethyl-Nʺ-phenylguanidine (a8). Yield 1.08 g (78%); light
blue solid; m. p. 162-163 °C; FT-IR (KBr, cm-1): 3389, 3152, 3056, 2973, 1592, 1577,
1460, 1367, 1072, 742, 540, 437; Anal. Calcd. for CuC28H40N6O2: (556.20); Cu,
11.42; C, 60.46; H, 7.25; N, 15.11; Found: Cu, 11.13; C, 60.21; H, 7.28; N, 15.03%; µ
eff. 1.73 BM.
2.5.2.9 Bis(N-pivaloyl-N′-(n-propyl)-N″-phenylguanidinato)copper(II) (A9)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.31 g
(5.0 mmol) N-pivaloyl-Nʹ-(n-propyl)-Nʺ-phenylguanidine (a9). Yield 1.10 g (75%);
light blue solid; m. p. 157-158 °C; FT-IR (KBr, cm-1): 3389, 3141, 3057, 2987, 1618,
1558, 1451, 1369, 1058, 849, 529, 437; Anal. Calcd. for CuC30H44N6O2: (584.26); Cu,
10.88; C, 61.67; H, 7.59; N, 14.38; Found: Cu, 10.62; C, 61.39; H, 7.45; N, 14.42%; µ
eff. 1.72 BM.
2.5.2.10 Bis(N-pivaloyl-N′-(n-butyl)-N″-phenylguanidinato)copper(II) (A10)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.38 g
(5.0 mmol) N′-pivaloyl-N′-(n-butyl)-N″-phenylguanidine (a10). Yield 1.21 g (79%);
light blue solid; m. p. 177-178 ºC; FT-IR (KBr, cm-1): 3441, 3059, 2959, 2937, 2868,
64
1561, 1524, 1461, 1341, 1229, 918, 543, 490; Anal. Calcd. for CuC32H48N6O2:
(612.31); Cu, 10.38; C, 62.77; H, 7.90; N, 13.73; Found: Cu, 10.15; C, 62.37; H, 7.73;
N, 13.52%; µ eff. 1.78 BM.
2.5.2.11 Bis(N-pivaloyl-N′-(iso-propyl)-N″-phenylguanidinato)copper(II) (A11)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.31 g
(5.0 mmol) N-pivaloyl-Nʹ-(iso-propyl)-Nʺ-phenylguanidine (a11). Yield 1.14 g
(78%); blue solid; m. p. 150-151 °C; FT-IR (KBr, cm-1): 3409, 3132, 3058, 2964,
1629, 1571, 1462, 1379, 1205, 838, 528, 437; Anal. Calcd. for CuC30H44N6O2:
(584.26); Cu, 10.88; C, 61.67; H, 7.59; N, 14.38; Found: Cu, 10.56; C, 61.58; H, 7.62;
N, 14.47%; µ eff. 1.66 BM.
2.5.2.12 Bis(N-pivaloyl-N′-(sec-butyl)-N″-phenylguanidinato)copper(II) (A12)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.38 g
(5.0 mmol) N-pivaloyl-N′-(sec-butyl)-N″-phenylguanidine (a12). Yield 1.24 g (81%);
light blue solid; m. p. 169-170 °C; FT-IR (KBr, cm-1): 3391, 3153, 3057, 2981, 1613,
1553, 1369, 1267, 759, 531, 437; Anal. Calcd. for CuC32H48N6O2: (612.31); Cu,
10.38; C, 62.77; H, 7.90; N, 13.73; Found: Cu, 10.02; C, 62.56; H, 7.87; N, 13.51%; µ
eff. 1.63 BM.
2.5.2.13 Bis(N-pivaloyl-N′-benzyl-N″-phenylguanidinato)copper(II) (A15)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.55 g
(5.0 mmol) N-pivaloyl-Nʹ-benzyl-Nʺ-phenylguanidine (a15). Yield 1.28 g (75%); blue
solid; m. p. 167-168 °C; FT-IR (KBr, cm-1): 3431, 3057, 2956, 2924, 2865, 1558,
1523, 1462, 1344, 926, 731, 529, 455; Anal. Calcd. for CuC38H44N6O2: (680.34); Cu,
9.34; C, 67.08; H, 6.52; N, 12.35; Found: Cu, 9.13; C, 66.84; H, 6.38; N, 12.41%; µ
eff. 1.54 BM.
2.5.2.14 Bis(N-pivaloyl-N′-(2,5-dichlorophenyl)-N″-phenylguanidinato)copper
(II) (A16)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.82 g
(5.0 mmol) N-pivaloyl-N′-(2,5-dichlorophenyl)-N″-phenylguanidine (a16). Yield 1.36
g (69%); light blue solid; m. p. 204-205 °C; FT-IR (KBr, cm-1): 3372, 3121, 2956,
2928, 2866, 1585, 1551, 1514, 1462, 1391, 1228, 948, 698, 532, 444; Anal. Calcd. for
CuC36H36N6O2Cl4: (790.07); Cu, 8.04; C, 54.73; H, 4.59; N, 10.64; Found: Cu, 8.21;
C, 54.36; H, 4.52; N, 10.71%; µ eff. 1.43 BM.
65
2.5.2.15 Bis(N-pivaloyl-N′-(2,4-dichlorophenyl)-N″-phenylguanidinato)copper
(II) (A17)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.82 g
(5.0 mmol) N-pivaloyl-N′-(2,4-dichlorophenyl-N″-phenylguanidine (a17). Yield 1.40
g (71%); blue solid; m. p. 210-211 °C; FT-IR (KBr, cm-1): 3381, 2955, 2932, 1585,
1553, 1466, 1350, 1298, 943, 699, 509, 443; Anal. Calcd. for CuC36H36N6O2Cl4:
(790.07); Cu, 8.04; C, 54.73; H, 4.59; N, 10.64; Found: Cu,8.23; C, 54.38; H, 4.57; N,
10.75%; µ eff. 1.48 BM.
2.5.2.16 Bis(N-pivaloyl-N′-(3,4-dichlorophenyl)-N″-phenylguanidinato)copper
(II) (A18)
Quantities used were 0.5 g (2.5 mmol) copper(II) acetate monohydrate and 1.82 g (5.0
mmol) N-pivaloyl-N′-(3,4-dichlorophenyl)-N″-phenylguanidine (a18). Yield 1.38 g
(70%); blue solid; m. p. 217-218 ºC; FT-IR (KBr, cm-1): 3372, 3047, 2958, 2943,
1592, 1561, 1457, 1369, 1191, 848, 521, 432; Anal. Calcd. for CuC36H36N6O2Cl4:
(790.07); Cu, 8.04; C, 54.73; H, 4.59; N, 10.64; Found: Cu, 7.96; C, 54.41; H, 4.52;
N, 10.51%; µ eff. 1.59 BM.
2.5.2.17 Bis(N-pivaloyl-N′-(3,5-dichlorophenyl)-N″-phenylguanidinato)copper
(II) (A19)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.82 g
(5.0 mmol) N-pivaloyl-N′-(3,5-dichlorophenyl)-N″-phenylguanidine (a19). Yield 1.42
g (72%); blue solid; m. p. 197-198 °C; FT-IR (KBr, cm-1): 3389, 3128, 3062, 2983,
1587, 1545, 1453, 1368, 1192, 983, 773; 515, 424; Anal. Calcd. for
CuC36H36N6O2Cl4: (790.07); Cu, 8.04; C, 54.73; H, 4.59; N, 10.64; Found: Cu, 8.26;
C, 54.38; H, 4.56; N, 10.72%; µ eff. 1.51 BM.
2.5.2.18 Bis(N-pivaloyl-N′-(2,3-dimethylphenyl)-N″-phenylguanidinato)copper
(II) (A20)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.62 g
(5.0 mmol) N-pivaloyl-Nʹ-(2,3-dimethylphenyl)-Nʺ-phenylguanidine (a20). Yield
1.24 g (70%); light blue solid; m. p. 171-172 °C; FT-IR (KBr, cm-1): 3388, 2951,
2923, 2862, 1592, 1555, 1492, 1426, 1350, 948, 695, 546, 489; Anal. Calcd. for
CuC40H48N6O2: (708.39); Cu, 8.97; C, 67.82; H, 6.83; N, 11.86; Found: Cu, 8.85; C,
67.74; H, 6.74;N, 11.78%; µ eff. 1.65 BM.
66
2.5.2.19 Bis(N-pivaloyl-N′-(3-methoxyphenyl)-N″-phenylguanidinato)copper(II)
(A21)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.63 g
(5.0 mmol) N-pivaloyl-Nʹ-(3-methoxyphenyl)-Nʺ-phenylguanidine (a21). Yield 1.35 g
(76%); light blue solid; m. p. 169-170 °C; FT-IR (KBr, cm-1): 3391, 3019, 2961,
2948, 1578, 1543, 1460, 1382, 963, 708, 529, 453; Anal. Calcd. for CuC38H44N6O4:
(712.34); Cu, 8.92; C, 64.07; H, 6.23; N, 11.80; Found: Cu, 8.71; C, 63.93; H, 6.16;
N, 11.67%; µ eff. 1.64 BM.
2.5.2.20 Bis(N-pivaloyl-N′-(tert-butyl)-N″-phenylguanidinato)copper(II) (A22)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.38 g
(5.0 mmol) N-pivaloyl-Nʹ-(tert-butyl)-Nʺ-phenylguanidine (a22). Yield 1.13 g (74%);
light blue solid; m. p. 156-157 °C; FT-IR (KBr, cm-1): 3387, 3137, 3034, 2976, 1608,
1562, 1452, 1369, 1187, 958, 721, 528, 431; Anal. Calcd. for CuC32H48N6O2:
(612.31); Cu, 10.38; C, 62.77; H, 7.90; N, 13.73; Found: Cu, 10.05; C, 62.36; H, 7.83;
N, 13.80%; µ eff. 1.71 BM.
2.5.2.21 Bis(N-pivaloyl-N′-(o-tolyl)-N″-phenylguanidinato)copper(II) (A27)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.55 g
(5.0 mmol) N-pivaloyl-Nʹ-(o-tolyl)-Nʺ-phenylguanidine (a27). Yield 1.26 g (74%);
blue solid; m. p. 177-178 °C; FT-IR (KBr, cm-1): 3407, 3157, 3079, 2986, 1618, 1538,
1449, 1365, 1043, 857, 529, 438; Anal. Calcd. for CuC38H44N6O2: (680.34); Cu, 9.34;
C, 67.08; H, 6.52; N, 12.35; Found: Cu, 9.45; C, 66.81; H, 6.55; N, 12.28%; µ eff.
1.66 BM.
2.5.2.22 Bis(N-pivaloyl-N′-cyclohexyl-N″-phenylguanidinato)copper(II) (A28)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.51 g
(5.0 mmol) N-pivaloyl-Nʹ-cyclohexyl-Nʺ-phenylguanidine (a28). Yield 1.13 g (68%);
blue solid; m. p. 205-206 °C; FT-IR (KBr, cm-1): 3416, 2929, 2853, 1561, 1522, 1447,
1393, 1358, 1210, 936, 540, 504; Anal. Calcd. for CuC36H52N6O2: (664.38); Cu, 9.56;
C, 65.08; H, 7.89; N, 12.65; Found: Cu, 9.27; C, 64.84; H, 7.78; N, 12.79%; µ eff.
1.63 BM.
2.5.3 Synthesis and characterization of Bis(N-pivaloyl-N′-(alkyl/aryl)-N″-
pyridylguanidinato)copper(II) complexes (B1-B29)
One equivalent of methanolic solution of copper(II) acetate was mixed with two
equivalent of methanolic solution of N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-pyridylguanidine
67
(b1-b29) with constant stirring at room temperature for 3-4 hours. The Bis(N-
pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-pyridylguanidinato)copper(II) complexes (B1-B29) were
formed as precipitate which were filtered and washed with methanol. The synthesized
complexes were further purified by recrystallization in dichloromethane. The reaction
scheme is given in figure 2.7.
Figure 2.7: Synthesis scheme for bis(N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-pyridylguani-
dinato)copper(II) complexes.
2.5.3.1 Bis(N-pivaloyl-N′-phenyl-N″-pyridylguanidinato)copper(II) (B1)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.48 g
(5.0 mmol) N-pivaloyl-Nʹ-phenyl-Nʺ-pyridylguanidine (b1). Yield 1.28 g (78%); blue
solid; m. p. 156-157 °C; FT-IR (KBr, cm-1): 3398, 3132, 2991, 1602, 1519, 1448,
1382, 1186, 836, 509, 422; Anal. Calcd. for CuC34H38N8O2: (654.26); Cu, 9.71; C,
62.42; H, 5.85; N, 17.13; Found: Cu, 9.84; C, 62.09; H, 5.81; N, 17.25%. µ eff. 1.49
BM.
2.5.3.2 Bis(N-pivaloyl-N′-(2-chlorophenyl)-N″-pyridylguanidinato)copper(II)
(B2)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.66 g
(5.0 mmol) N-pivaloyl-Nʹ-(2-chlorophenyl)-Nʺ-pyridylguanidine (b2). Yield 1.34 g
(74%); blue solid; m. p. 163-164 °C; FT-IR (KBr, cm-1): 3422, 3162, 3047, 2956,
1601, 1528, 1461, 1392, 928, 872, 511, 429; Anal. Calcd. for CuC34H36N8O2Cl2:
(723.15); Cu, 8.79; C, 56.47; H, 5.02; N, 15.50; Found: Cu, 8.63; C, 56.16; H, 5.12;
N, 15.31%; µ eff. 1.52 BM.
2.5.3.3 Bis(N-pivaloyl-N′-(3-chlorophenyl-N″-pyridylguanidinato)copper(II)
(B3)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.66 g
(5.0 mmol) N-pivaloyl-Nʹ-(3-chlorophenyl)-Nʺ-pyridylguanidine (b3). Yield 1.39 g
68
(77%); blue solid; m. p. 170-171 °C; FT-IR (KBr, cm-1): 3413, 3137, 3064, 2957,
1595, 1549, 1456, 1381, 1189, 926, 825, 523, 431; Anal. Calcd. for
CuC34H36N8O2Cl2: (723.15); Cu, 8.79; C, 56.47; H, 5.02; N, 15.50; Found: Cu, 8.57;
C, 56.02; H, 5.13; N, 15.42%; µ eff. 1.50 BM.
2.5.3.4 Bis(N-pivaloyl-N′-(4-chlorophenyl)-N″-pyridylguanidinato)copper(II)
(B4)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.66 g
(5.0 mmol) N-pivaloyl-Nʹ-(4-chlorophenyl)-Nʺ-pyridylguanidine (b4). Yield 1.36 g
(75%); blue solid; m. p. 169-170 °C, FT-IR (KBr, cm-1): 3405, 3125, 3062, 2949,
1590, 1556, 1459, 1372, 1028, 851, 520, 437; Anal. Calcd. for CuC34H36N8O2Cl2:
(723.15); Cu, 8.79; C, 56.47; H, 5.02; N, 15.50; Found: Cu, 8.83; C, 56.28; H, 4.96;
N, 15.61%; µ eff. 1.54 BM.
2.5.3.5 Bis(N-pivaloyl-N′-(2-methoxyphenyl)-N″-pyridylguanidinato)copper(II)
(B5)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.63 g
(5.0 mmol) N-pivaloyl-Nʹ-(2-methoxyphenyl)-Nʺ-pyridylguanidine (b5). Yield 1.29 g
(72%); blue solid; m. p. 175-176 ºC; FT-IR (KBr, cm-1): 3399, 3156, 3047, 2968,
1604, 1539, 1472, 1377, 1098, 852, 525, 429; Anal. Calcd. for CuC36H42N8O4:
(714.32); Cu, 8.90; C, 60.53; H, 5.93; N, 15.69; Found: Cu, 8.57; C, 60.12; H, 5.97;
N, 15.37%; µ eff. 1.59 BM.
2.5.3.6 Bis(N-pivaloyl-N′-( p-tolyl)-N″-pyridylguanidinato)copper(II) (B6)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.55 g
(5.0 mmol) N-pivaloyl-Nʹ-(p-tolyl)-Nʺ-pyridylguanidine (b6). Yield 1.30 g (76%);
blue solid; m. p. 151-152 °C; FT-IR (KBr, cm-1): 3397, 3153, 3031, 2948, 1593, 1551,
1468, 1368, 1187, 934, 847, 518, 436; Anal. Calcd. for CuC36H42N8O2: (682.32); Cu,
9.31; C, 63.37; H, 6.20; N, 16.42; Found: Cu, 9.68; C, 63.02; H, 6.15; N, 16.53%; µ
eff. 1.61 BM.
2.5.3.7 Bis(N-pivaloyl-N′-(2-fluorophenyl)-N″-pyridylguanidinato)copper(II)
(B7)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.57 g
(5.0 mmol) N-pivaloyl-Nʹ-(2-fluorophenyl)-Nʺ-pyridylguanidine (b7). Yield 1.21 g
(70%); blue solid; m. p. 161-162 °C; FT-IR (KBr, cm-1): 3399, 3149, 3054, 2948,
69
1585, 1567, 1460, 1371, 1087, 882, 538, 419; Anal. Calcd. for CuC34H36N8O2F2:
(690.24); Cu, 9.21; C, 59.16; H, 5.26; N, 16.23; Found: Cu, 9.42; C, 58.85; H, 5.30;
N, 16.04%; µ eff. 1.47 BM.
2.5.3.8 Bis(N-pivaloyl-N′-ethyl-N″-pyridylguanidinato)copper(II) (B8)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.24 g
(5.0 mmol) N-pivaloyl-Nʹ-ethyl-Nʺ-pyridylguanidine (b8). Yield 1.09 g (78%); light
blue solid; m. p. 140-141 °C; FT-IR (KBr, cm-1): 3403, 3145, 3050, 2967, 1594, 1553,
1461, 1365, 1007, 858, 516, 430; Anal. Calcd. for CuC26H38N8O2: (558.18); Cu,
11.38; C, 55.95; H, 6.86; N, 20.07; Found: Cu, 11.07; C, 55.63; H, 6.75; N,19.94%; µ
eff. 1.60 BM.
2.5.3.9 Bis(N-pivaloyl-N′-(n-propyl)-N″-pyridylguanidinato)copper(II) (B9)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.31 g
(5.0 mmol) N-pivaloyl-Nʹ-(n-propyl)-Nʺ-pyridylguanidine (b9). Yield 1.13 g (77%);
light blue solid; m. p. 138-139 °C; FT-IR (KBr, cm-1): 3408, 3067, 2977, 1584, 1547,
1432, 1380, 1207, 1049, 827, 510, 438; Anal. Calcd. for CuC28H42N8O2: (586.23); Cu,
10.84; C, 57.37; H, 7.22; N, 19.11; Found: Cu, 10.62; C, 57.01; H, 7.27; N, 19.22%; µ
eff. 1.72 BM.
2.5.3.10 Bis(N-pivaloyl-N′-(n-butyl)-N″-pyridylguanidinato)copper(II) (B10)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.38 g
(5.0 mmol) N-pivaloyl-N′-(n-butyl)-N″-pyridylguanidine (b10). Yield 1.14 g (74%);
light blue solid; m. p. 141-142 ºC; FT-IR (KBr, cm-1): 3396, 3152, 3058, 2968, 1582,
1549, 1456, 1361, 1187, 954, 527, 437; Anal. Calcd. for CuC30H46N8O2: (614.28); Cu,
10.34; C, 58.66; H, 7.55; N, 18.24; Found: Cu, 10.67; C, 58.23; H, 7.51; N, 18.01%; µ
eff. 1.73 BM.
2.5.3.11 Bis(N-pivaloyl-N′-(iso-propyl)-N″-pyridylguanidinato)copper(II) (B11)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.31 g
(5.0 mmol) N-pivaloyl-Nʹ-(iso-propyl)-Nʺ-pyridylguanidine (b11). Yield 1.13 g
(77%); light blue solid; m. p. 152-153 °C; FT-IR (KBr, cm-1): 3396, 3144, 3048,
2970, 1591, 1560, 1467, 1369, 1153, 839, 519, 422; Anal. Calcd. for CuC28H42N8O2:
(586.23); Cu, 10.84; C, 57.37; H, 7.22; N, 19.11; Found: Cu, 11.04; C, 57.01; H, 7.33;
N, 19.32%; µ eff. 1.63BM.
70
2.5.3.12 Bis(N-pivaloyl-N′-(sec-butyl)-N″-pyridylguanidinato)copper(II) (B12)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.38 g
(5.0 mmol) N-pivaloyl-N′-(sec-butyl)-N″-pyridylguanidine (b12). Yield 1.21 g (79%);
light blue solid; m. p. 144-145 ºC; FT-IR (KBr, cm-1): 3408, 3145, 3063, 2959, 1593,
1554, 1453, 1378, 1147, 1024, 864, 531, 424; Anal. Calcd. for CuC30H46N8O2:
(614.28); Cu, 10.34; C, 58.66; H, 7.55; N, 18.24; Found: Cu, 10.81; C, 58.29; H, 7.67;
N, 18.03%; µ eff .1.66 BM.
2.5.3.13 Bis(N-pivaloyl-N′-benzyl-N″-pyridylguanidinato)copper(II) (B15)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.55 g
(5.0 mmol) N-pivaloyl-Nʹ-benzyl-Nʺ-pyridylguanidine (b15). Yield 1.26 g (74%);
blue solid; m. p. 147-148 °C; FT-IR (KBr, cm-1): 3418, 3141, 3057, 2949, 1596, 1553,
1458, 1372, 1147, 953, 764, 513, 427; Anal. Calcd. for CuC36H42N8O2: (682.32); Cu,
9.31; C, 63.37; H, 6.20; N, 16.42; Found: Cu, 9.52; C, 63.13; H, 6.23; N, 16.31%; µ
eff. 1.54BM.
2.5.3.14 Bis(N-pivaloyl-N′-(2,5-dichlorophenyl)-N″-pyridylguanidinato)copper
(II) (B16)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.83 g
(5.0 mmol) N-pivaloyl-N′-(2,5-dichlorophenyl)-N″-pyridylguanidine (b16). Yield
1.45 g (73%); blue solid; m. p. 177-178 °C; FT-IR (KBr, cm-1): 3398, 3147, 2978,
2952, 1583, 1539, 1463, 1377, 1148, 959, 774, 508, 425; Anal. Calcd. for
CuC34H34N8O2Cl4: (792.04); Cu, 8.02; C, 51.56; H, 4.33; N, 14.15; Found: Cu, 8.41;
C, 51.23; H, 4.40; N, 14.26%; µ eff. 1.51 BM.
2.5.3.15 Bis(N-pivaloyl-N′-(2,4-dichloropheny)-N″-pyridylguanidinato)copper
(II) (B17)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.83 g
(5.0 mmol) N-pivaloyl-N′-(2,4-dichlorophenyl)-N″-pyridylguanidine (b17). Yield
1.37 g (69%); blue solid; m. p. 164-165 °C; FT-IR (KBr, cm-1): 3417, 3153, 3047,
2939, 1605, 1559, 1471, 1367, 1228, 1126, 929, 878, 512, 428; Anal. Calcd. for
CuC34H34N8O2Cl4: (792.04); Cu, 8.02; C, 51.56; H, 4.33; N, 14.15; Found: Cu, 8.37;
C, 51.32; H, 4.29; N, 14.35%; µ eff. 1.57 BM.
71
2.5.3.16 Bis(N-pivaloyl-N′-(3,4-dichlorophenyl)-N″-pyridylguanidinato)copper
(II) (B18)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.83 g
(5.0 mmol) N-pivaloyl-N′-(3,4-dichlorophenyl)-N″-pyridylguanidine (b18). Yield
1.39 g (70%); blue solid; m. p. 173-174 °C; FT-IR (KBr, cm-1): 3408, 3143, 3058,
2942, 1586, 1549, 1453, 1378, 1237, 948, 858, 518, 423; Anal. Calcd. for
CuC34H34N8O2Cl4: (792.04); Cu, 8.02; C, 51.56; H, 4.33; N, 14.15; Found: Cu, 7.92;
C, 51.34; H, 4.38; N, 14.01%; µ fee. 1.63 BM.
2.5.3.17 Bis(N-pivaloyl-N′-(3,5-dichlorophenyl)-N″-pyridylguanidinato)copper
(II) (B19)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.83 g
(5.0 mmol) N-pivaloyl-N′-(3,5-dichlorophenyl)-N″-pyridylguanidine (b19). Yield
1.35 g (68%); blue solid; m. p. 170-171 °C; FT-IR (KBr, cm-1): 3412, 3152, 3061,
2959, 1586, 1538, 1452, 1377, 1237, 1052, 863, 507, 427; Anal. Calcd. for
CuC34H34N8O2Cl4: (792.04); Cu, 8.02; C, 51.56; H, 4.33; N, 14.15; Found: Cu, 8.17;
C, 51.63; H, 4.22; N, 14.24%; µ eff. 1.66 BM.
2.5.3.18 Bis(N-pivaloyl-N′-(2,3-dimethylphenyl)-N″-pyridylguanidinato)copper
(II) (B20)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.62 g
(5.0 mmol) N-pivaloyl-Nʹ-(2,3-dimethylphenyl)-Nʺ-pyridylguanidine (b20). Yield
1.33 g (75%); blue solid; m. p. 157-158 °C; FT-IR (KBr, cm-1): 3407, 3148, 3039,
2958, 1594, 1562, 1458, 1379, 1228, 1067, 874, 523, 417; Anal. Calcd. for
CuC38H46N8O2: (710.37); Cu, 8.95; C, 64.25; H, 6.53; N, 15.77; Found: Cu, 9.12; C,
63.83; H, 6.60; N, 15.51%; µ eff. 1.69 BM.
2.5.3.19 Bis(N-pivaloyl-N′-(3-methoxyphenyl)-N″-pyridylguanidinato)copper(II)
(B21)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.63 g
(5.0 mmol) N-pivaloyl-Nʹ-(3-methoxyphenyl)-Nʺ-pyridylguanidine (b21). Yield 1.30
g (73%); blue solid; m. p. 181-182 °C; FT-IR (KBr, cm-1): 3417, 3152, 3048, 2957,
1596, 1543, 1467, 1371, 1137, 1058, 837, 510, 434; Anal. Calcd. for CuC36H42N8O4:
(714.32); Cu, 8.90; C, 60.53; H, 5.93; N, 15.69; Found: Cu, 8.52; C, 60.28; H, 5.99;
N, 15.74%; µ eff. 1.49 BM.
72
2.5.3.20 Bis(N-pivaloyl-N′-(tert-butyl)-N″-pyridylguanidinato)copper(II) (B22)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.38 g
(5.0 mmol) N-pivaloyl-Nʹ-(tert-butyl)-Nʺ-pyridylguanidine (b22). Yield 1.18 g (77%);
light blue solid; m. p. 145-146 ºC; FT-IR (KBr, cm-1): 3407, 3147, 3061, 2953, 1604,
1543, 1457, 1360, 1127, 842, 505, 418; Anal. Calcd. for CuC30H46N8O2: (614.28); Cu,
10.34; C, 58.66; H, 7.55; N, 18.24; Found: Cu, 10.60; C, 58.32; H, 7.60; N, 18.11%; µ
eff. 1.71 BM.
2.5.3.21 Bis(N-pivaloyl-N′-(o-tolyl)-N″-pyridylguanidinato)copper(II) (B27)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.55 g
(5.0 mmol) N-pivaloyl-Nʹ-(o-tolyl)-Nʺ-pyridylguanidine (b27). Yield 1.26 g (74%);
blue solid; m. p. 152-153 °C; FT-IR (KBr, cm-1): 3415, 3153, 3064, 2957, 1608, 1548,
1444, 1368, 1149, 956, 842, 508, 418; Anal. Calcd. for CuC36H42N8O2: (682.32); Cu,
9.31; C, 63.37; H, 6.20; N, 16.42; Found: Cu, 9.02; C, 63.21; H, 6.27; N, 16.57%; µ
eff. 1.68 BM.
2.5.3.22 Bis(N-pivaloyl-N′-cyclohexyl-N″-pyridylguanidinato)copper(II) (B28)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.51 g
(5.0 mmol) N-pivaloyl-Nʹ-cyclohexyl-Nʺ-pyridylguanidine (b28). Yield 1.17 g (70%);
blue solid; m. p. 170-171 °C; FT-IR (KBr, cm-1): 3407, 3148, 3061, 2953, 1597, 1548,
1463, 1370, 1178, 929, 516, 422; Anal. Calcd. for CuC34H50N8O2: (666.36); Cu, 9.54;
C, 61.28; H, 7.56; N, 16.82; Found: Cu, 9.72; C, 61.39; H, 7.51; N, 16.59% µ eff.
1.53 BM.
2.5.3.23 Bis(N-pivaloyl-N′,N″-bipyridylguanidinato)copper(II) (B29)
Quantities used were 0.50 g (2.5 mmol) copper(II) acetate monohydrate and 1.49 g
(5.0 mmol) N-pivaloyl-Nʹ,Nʺ-bipyridylguanidine (b29). Yield 1.23 g (75%); blue
solid; m. p. 156-157 °C; FT-IR (KBr, cm-1): 3411, 3054, 2959, 1593, 1537, 1445,
1376, 1167, 942, 511, 425; Anal. Calcd. for CuC32H36N10O2: (656.24); Cu, 9.68; C,
58.57; H, 5.53; N, 21.34; Found: Cu, 9.37; C, 58.60; H, 5.46; N, 21.22%; µ eff. 1.43
BM.
73
2.6 Synthesis and characterization of Ni(II) complexes of
guanidines
2.6.1 Synthesis and characterization of Bis(N-pivaloyl-N′-(alkyl/aryl)-N˝-
phenylguanidinato)nickel(II) complexes (Nia1-Nia9)
One equivalent of ethanolic solution of nickel(II) chloride was mixed with two
equivalents of an ethanolic solution of N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-phenylguanidine
(a1-a9) with constant stirring at room temperature. The reaction mixture was refluxed
for 72 hours under inert atmosphere. The Bis(N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-
phenylguanidinato)nickel(II) complexes (Nia1-Nia9) were formed as pink
precipitates which were filtered and washed with ethanol. The reaction scheme is
given in figure 2.8:
Figure 2.8: Synthesis scheme for bis(N-pivaloyl-Nʹ-(alkyl/aryl)-Nʺ-
phenylguanidinato)nickel(II) complexes.
2.6.1.1 Bis(N-pivaloyl-N′,N″-diphenylguanidinato)nickel(II) (Nia1)
Quantities used were 0.32 g (2.5 mmol) nickel(II) chloride anhydrous and 1.48 g (5.0
mmol) N-pivaloyl-Nʹ,Nʺ-diphenylguanidine (1a). Yield 0.91 g (56%); pink solid; m.
p. 261-262 °C; FT-IR (KBr, cm-1): 3438, 3126, 2965, 1665, 1542, 1349, 876, 512,
445; Anal. Calcd. for NiC36H40N6O2: (647.44); Ni, 9.07; C, 66.78; H, 6.23; N, 12.98;
Found: Ni, 9.13; C, 66.72; H, 6.19; N, 12.87%.
2.6.1.2 Bis(N-pivaloyl-Nʹ-(2-chlorophenyl)-Nʺ-phenylguanidinato)nickel(II)
(Nia2)
Quantities used were 0.32 g (2.5 mmol) nickel(II) chloride anhydrous and 1.65 g (5.0
mmol) N-pivaloyl-N′-(2-chlorophenyl)-N″-phenylguanidine (2a). Yield 0.86 g (48%);
pink solid; m. p. 209-210 ºC; FT-IR (KBr, cm-1): 3424, 3136, 2967, 1649, 1420, 1352,
74
871, 747, 525, 455; Anal. Calcd. for NiC36H38N6O2Cl2: (716.33); Ni, 8.19; C, 60.36;
H, 5.35; N, 11.73; Found: Ni, 8.25; C, 59.97; H, 5.27; N, 11.68%.
2.6.1.3 Bis(N-pivaloyl-Nʹ-(3-chlorophenyl)-Nʺ-phenylguanidinato)nickel(II)
(Nia3)
Quantities used were 0.32 g (2.5 mmol) nickel(II) chloride anhydrous and 1.65 g (5.0
mmol) N-pivaloyl-N′-(3-chlorophenyl)-N″-phenylguanidine (3a). Yield 0.93 g (52%);
pink solid; m. p. 245-246 °C; FT-IR (KBr, cm-1): 3387, 3089, 2962, 1605, 1503,
1445, 1357, 1253, 881, 753, 532, 439; Anal. Calcd. for NiC36H38N6O2Cl2: (716.33);
Ni, 8.19 ; C, 60.36; H, 5.35; N, 11.73; Found: Ni, 8.13; C, 59.99; H, 5.29; N, 11.32%.
2.6.1.4 Bis(N-pivaloyl-Nʹ-(4-chlorophenyl)-Nʺ-phenylguanidinato)nickel(II)
(Nia4)
Quantities used were 0.32 g (2.5 mmol) nickel(II) chloride anhydrous and 1.65 g (5.0
mmol) N-pivaloyl-Nʹ-(4-chlorophenyl)-Nʺ-phenylguanidine (a4). Yield 0.95 g (53%);
pink solid; m. p. 212-213 °C; FT-IR (KBr, cm-1): 3373, 3071, 2968, 1606, 1533,
1452, 851, 541, 437; Anal. Calcd. for NiC36H38N6O2Cl2: (716.33); Ni, 8.19 ; C, 60.36;
H, 5.35; N, 11.73; Found: Ni, 8.23; C, 60.01; H, 5.32; N, 11.67%.
2.6.1.5 Bis(N-pivaloyl-Nʹ-(2-methoxyphenyl)-Nʺ-phenylguanidinato)nickel(II)
(Nia5)
Quantities used were 0.32 g (2.5 mmol) nickel(II) chloride anhydrous and 1.63 g (5.0
mmol) N-pivaloyl-Nʹ-(2-methoxyphenyl)-Nʺ-phenylguanidine (a5). Yield 0.80 g
(45%); pink solid; m. p. 241-242 °C; FT-IR (KBr, cm-1): 3351, 3067, 2958, 1571,
1465, 1387, 882, 546, 432; Anal. Calcd. for NiC38H44N6O4: (707.49); Ni, 8.30; C,
64.51; H, 6.27; N, 11.88; Found: Ni, 8.25; C, 64.34; H, 6.23; N, 11.79%.
2.6.1.6 Bis(N-pivaloyl-Nʹ-ethyl-Nʺ-phenylguanidinato)nickel(II) (Nia8)
Quantities used were 0.32 g (2.5 mmol) nickel(II) chloride anhydrous and 1.24 g (5.0
mmol) N-pivaloyl-Nʹ-ethyl-Nʺ-phenylguanidine (a8). Yield 0.65 g (47%); pink solid;
m. p. 243-244 °C; FT-IR (KBr, cm-1): 3376, 3062, 2967, 1608, 1548, 1455, 1372,
871, 551, 442; Anal. Calcd. for NiC28H40N6O2: (551.35); Ni, 10.65; C, 61.00; H, 7.31;
N, 15.24; Found: Ni, 10.58; C, 60.89; H, 7.25; N, 15.18%.
2.6.1.7 Bis(N-pivaloyl-N′-(n-propyl)-N″-phenylguanidinato)nickel(II) (Nia9)
Quantities used were 0.32 g (2.5 mmol) nickel(II) chloride anhydrous and 1.31 g (5.0
mmol) N-pivaloyl-Nʹ-(n-propyl)-Nʺ-phenylguanidine (a9). Yield 0.74 g (51%); pink
75
solid; m. p. 231-232 °C; FT-IR (KBr, cm-1): 3374, 3068, 2972, 1609, 1534, 1462,
1345, 871, 548, 446; Anal. Calcd. for NiC30H44N6O2: (579.40); Ni, 10.13; C, 62.19;
H, 7.65; N, 14.50; Found: Ni, 10.01; C, 61.97; H, 7.53; N, 14,39%.
References
1. Armarego, W.L.F.; Chai, C.L.L., Purification of Laboratory Chemicals, 5th Ed.,
Butterworth Heinemann, London, New York, 2003.
2. Gottlieb, H.E.; Kotlyar, V.; Nudelman, A., J. Org. Chem. 1997, 62, 7512.
3. Rauf, M. K.; Imtiaz-ud-Din; Badshah, A.; Gielen, M.; Ebihara, M.; de Vos, D.;
Ahmed, S., J. Inorg. Biochem. 2009, 103, 1135.
4. Murtaza, G.; Badshah, A.; Said, M.; Khan, H.; Khan, A.; Khan, S.; Siddiq, S.;
Choudhary, M.I.; Boudreau, J.; Fontaine, F-G., Dalton Trans. 2011, 40, 9202.
5. Said, M.; Murtaza, G.; Freisinger, E.; Anwar, S.; Rauf, A., Acta Cryst. 2009, E65,
o2073.
76
Chapter-3
Results and Discussion
3.1 Elemental analysis
The percentages of carbon, hydrogen and nitrogen in the synthesized compounds were
determined with a Fisons EA1108 CHNS analyzer and an LECO-183 CHNS analyzer
while the percentage of copper in the complexes was determined by atomic absorption
spectroscopy using a Perkin Elmer 2380 Atomic Absorption Spectrophotometer. The
close agreement of the results between calculated values and experimental values,
confirmed the composition of the desired products. The elemental analysis was
particularly useful for the characterization of complexes which confirmed that the
ligand to metal ratio in the complexes as 2:1.
3.2 FT-IR spectroscopy
The FT-IR spectra were recorded for all the free ligands and complexes using
different IR spectrophotometers. The significant FT-IR bands recorded for all
synthesized compounds are given in chapter-2, along with other characterization data
of respective compounds. The tentative assignments of different FT-IR bands with
different functional groups were made according to the literature [1].
The synthesized guanidines can be classified into two types; i.e. tri-substituted
guanidines and tetra-substituted guanidines as given below:
Type-1; Tri-substituted guanidines
synthesized from the reaction of
primary amines with thiourea
Type-2; Tetra-substituted guanidines
synthesized from the reaction of
secondary amines with thiourea
Type-1 guanidines have two NH groups in a molecule while type-2 guanidines
have only one NH group per molecule. The presence of an Nʹ-H group in type-1 and
its absence in type-2 guanidines is very interesting. It was observed that only type-1
guanidines can form complexes with Cu(II) while type-2 guanidines do not form
complexes. The stereo-chemistry of both types will be discussed in the single crystal
X-ray diffraction analysis.
There are two NH bands in the FT-IR spectra for type-1 guanidines while only
one NH band for type-2 guanidines. For all guanidines, a sharp NH band appears in
77
the range of 3372 – 3447 cm-1 while a second medium and broader Nʹ-H band appears
in the range of 3203 – 3278 cm-1 in type-1 guanidines only. The Nʹ-H band appears at
lower frequency as compared to the NH band, which may be attributed to the
formation of intramolecular hydrogen boding between Nʹ-H and the oxygen atom of
the carbonyl group. As already stated, only type-1 guanidines can form complexes
with Cu(II), and the complexes have only one NH band in the range of 3362 – 3431
cm-1. The disappearance of other Nʹ-H bands after complexation indicate that
guanidines (type-1) undergo deprotonation and act as monoanionic ligands
(guanidinates (1-)) coordinating through the deprotonated nitrogen atom of the
guanidine moiety.
The stretching frequency for the C=O group in the ligands appears in the range
of 1583 – 1690 cm-1 which is at relatively lower frequency to normal amide groups
indicating the conjugation of the carbonyl group with the guanidine moiety and the
involvement of the C=O function in hydrogen bonding. The intramolecular hydrogen
bonding between the Nʹ-H group and the oxygen atom of the carbonyl group in the
ligands is confirmed by single crystal XRD technique as well. In the complexes, the
C=O band appears in the range of 1556 – 1650 cm-1 which is at relatively lower
frequency than in the free ligands. This decrease in frequency is an indication of the
involvement of the carbonyl group in complexation. From the IR data it is confirmed
that our ligands behave as bidentate ligands coordinating through one nitrogen atom
of the guanidine moiety and the oxygen of the carbonyl group.
A band in the range of 2932 – 2995 cm-1 is observed in all ligands and
complexes which is due to CH stretching frequencies of the tertiary butyl group. The
CH3 bending is observed at 1334 – 1370 cm-1 in all synthesized compounds.
3.3 Multi-nuclear (1H, 13C) NMR spectroscopy
The multinuclear (1H, 13C) NMR spectra were recorded only for the guanidine
compounds as all the Cu(II) complexes were paramagnetic in nature. The 1H and 13C
NMR data for the synthesized compounds is given in chapter-2, along with other
characterization data for each compound. The signals in the 1H and 13C NMR spectra
were assigned to different hydrogen and carbon atoms in relevant compounds
according to the literature.
There are two NH signals observed in the 1H NMR spectra of type-1
guanidines while only one NH signal is observed in type-2 guanidines. In the first
78
series of guanidines (a1-a28), one NH signal is observed in the range of δ = 10.18 –
12.83 ppm for all compounds while the second NH signal is observed at δ = 7.27 –
8.64 ppm in the type-1 guanidines. In the second series of guanidines (b1-b29), one
NH signal is observed in the range of δ = 14.35 – 14.59 ppm for all compounds while
the second NH signal is observed at δ = 8.48 – 12.27 ppm in the type-1 guanidines.
The NH protons are highly deshielded due to the conjugation of the guanidine moiety
with electron withdrawing carbonyl groups and also their involvement in
intramolecular hydrogen bonding. All NH signals are observed as broad singlets. The
NH signals are broad due to the quadrupole effect of nitrogen (S =1) [2] . In most of
the synthesized compounds, the aromatic protons give multiplet signals in the range
of δ = 6.17 – 7.98 ppm with few exceptions which are given in chapter 2. A large
singlet is observed at δ = 1.09 – 1.51 ppm for all guanidines representing nine protons
of the pivaloyl group.
13C NMR spectroscopy is an important technique used for structural
elucidation of synthesized compounds. In the 13C NMR spectra, the carbonyl carbon
atom was observed in the range of δ = 177.7 – 192.3 ppm for all synthesized
guanidines. This carbon atom is highly deshielded due to its attachment with the
highly electronegative oxygen atom on one side and the electron withdrawing
guanidine moiety on the other side. The central carbon atom of the CN3 group gives a
signal in the range of δ = 156.5 – 162.7 ppm in all synthesized free ligands which is
specific for the guanidine moiety [3]. The aromatic carbon atoms resonate in the range
of δ = 110.3 – 149.3 ppm which is very much comparable with literature reported
values [4]. There is a strong signal in the range of δ = 26.3 – 28.6 ppm representing
three magnetically equivalent carbon atoms of the tertiary butyl group of the pivaloyl
moiety in all free ligands. A signal for the central carbon atom of the tertiary butyl
group of the pivaloyl moiety is observed at δ = 40.0 – 42.0 ppm in all synthesized
guanidines. All the carbon atoms of aliphatic and aromatic groups are observed in
normal regions.
3.4 Magnetic susceptibility
In order to check the magnetic behavior of the synthesized complexes, their magnetic
susceptibility was determined by using magnetic susceptibility balance Auto MSB.
The instrument measured the mass susceptibility (χg) from which the effective
magnetic moment (μeff) was calculated using the following formula:
79
µeff = 2.828 x (χg x M.wt. x T)1/2
Where M.wt is the molecular weight of the compound and T is the absolute
temperature (K).
All copper(II) complexes were paramagnetic in nature. The values of the
effective magnetic moments (μeff) for all copper(II) complexes were found in the
range of 1.43 to 1.78 BM, which represents the presence of one unpaired electron in
each complex [5].
3.5 Single crystal X-ray diffraction analysis
Single crystal X-ray diffraction technique was used to find out the exact molecular
geometries of the synthesized compounds. Different diffractometers were used for
data collection and the structures were solved using different methods such as
SHELXS-97, SIR 92 [6] etc. which are mentioned along each crystal structure in the
coming pages.
3.5.1 Crystal structures of guanidines (ligands)
Crystals of various guanidines were grown in methanol/ethanol and suitable crystals
were used for solid state X-ray diffraction studies. The diagrams for molecular
structures of guanidines are given in figure 3.1 to 3.6. The crystallographic parameters
are given in tables 3.1 to 3.2 while the selected bond lengths, bond angles and torsion
angles are given in table 3.3
3.5.1.1 N-pivaloyl-N′,N″-diphenylguanidine (a1)
Colorless rod shaped crystal of a1 were grown in ethanol. The crystallographic data
for the compound was collected on a Bruker Microstar generator equipped with a
Kappa Nonius goniometer and platinum 135 detector. Cell refinement and data
reduction were done using SAINT [7]. The space group was confirmed by XPREP
routine [8] in the program SHELXTL [9]. The structure was solved by direct methods
and refined by full-matrix least-squares on F2 with SHELX-97 [10]. The molecular
structure is given in figure 3.1.
80
a b
Figure 3.1: (a) Diagram of a1 with atomic numbering scheme. (b) Diagram of a1
showing intramolecular hydrogen bondings.
The single crystal X-ray results show that a1 crystallizes in the triclinic P-1
space group with Z = 2. The guanidine core (NHC(=N)NH) in the molecule is
perfectly planar and the sum of angles around the central carbon atom is 360°. The Y-
aromaticity of the guanidine moiety can be observed from the C-N bond lengths
which are 1.281(2) A, 1.359(2) A and 1.415(2) A (Table 3.3). The C-N bond lengths
are longer than double bonds, C=N (1.25 – 1.28 A) [11] and smaller than single
bonds, C-N (1.45 – 1.47 A) [12]. Furthermore, the torsion angles O1-C5-N1-C6 (-2.6
(3)), C5-N1-C6-N2 (11.4(2)), and C5-N1-C6-N3 (-171.14(17)) indicate that the
carbonyl group and the guanidine moiety are almost coplanar (Table 3.3). This
planarity is very important for complexation because in case of the presence of the
carbonyl group and the guanidine group in a plane will make it suitable to act as
bidentate ligand coordinating through a de-protonated nitrogen atom of guanidine
moiety and oxygen atom of the carbonyl group. The single crystal X-ray results also
indicate the presence of intramolecular hydrogen bonding between the N2-H and the
oxygen atom of the carbonyl group forming a six membered ring.
3.5.1.2 N-Pivaloyl-Nʹ-(4-chlorophenyl)-Nʺ-phenylguanidine (a4)
A colorless block shaped crystal of a4 was analyzed with the same instrument used
for a1. The data collection, data reduction and structure refinement were done by
methods described for a1. The molecular structure of a4 is given in figure 3.2. Crystal
data and structure refinement parameters for a4 are given in table 3.1.
81
a b
Figure 3.2: (a) Diagram of a4 with atomic numbering scheme. (b) Diagram of a4
showing intramolecular hydrogen bondings.
The single crystal X-ray structure of a4 shows that the guanidine moiety is
resonance stabilized and perfectly planar. The sum of angles around the central
carbon atom in the guanidine group is 360°. The important bond angles are given in
table 3.3. The resonance in the guanidine moiety can be observed from the C-N bond
lengths given in table 3.3 which are an intermediate between a double bond (C=N)
and a single bond (C-N). Furthermore, the torsion angles O1-C5-N1-C6 (1.3˚), C5-
N1-C6-N2 (-13.5°), and C5-N1-C6-N3(170.3°) indicate that the carbonyl group and
the guanidine moiety are almost coplanar. Due to the presence of the carbonyl group
and the guanidine unit in a plane a4 behaves as a bidentate ligand coordinating
through a de-protonated nitrogen atom of the guanidine moiety and the oxygen atom
of the carbonyl group forming a six membered ring with a metal center. It is observed
from XRD results that the 4-chlorophenyl ring is slightly out of plane of the guanidine
unit while the phenyl ring is almost perpendicular to the guanidine group. The single
crystal X-ray results also indicate that the molecule is stabilized by the intramolecular
hydrogen bonding between N′-H and the oxygen atom of the carbonyl group.
3.5.1.3 N-pivaloyl-Nʹ-(2-methoxyphenyl)-Nʺ-phenylguanidine (a5)
The crystals of a5 grown in methanol were block shaped and colorless. A suitable
crystal was selected for X-ray diffraction studies and the crystallographic data was
collected on an Oxford diffraction Xcalibur R diffractometer equipped with an
Enhance (Mo) X-ray source and a graphite monochromator. The data collection and
data reduction were done using CrysAlis CCD [13] and CrysAlis RED [14]
82
respectively. The structure was solved by direct methods and refined by full-matrix
least-squares on F2 with SHELX-97. The molecular diagram for a5 is given in figure
3.3.
a b
Figure 3.3: (a) Diagram of a5 with atomic numbering scheme. (b) Diagram of a5
showing intramolecular hydrogen bondings.
The single crystal XRD results of a5 show the presence of a carbonyl group,
the guanidine moiety and an o-methoxyphenyl group attached to N1 in the same
plane. There is a strong resonance in the molecule due to the occurrence of the above
mentioned unsaturated groups in a plane. The delocalization of π electrons in the
compound is evident from bond lengths and bond angles which are given in table 3.3.
The phenyl ring present at N2 is almost perpendicular to the guanidine plane which is
obvious from the torsion angles given in table 3.3. In the solid state the molecule is
stabilized by an intramolecular hydrogen bond between N1-H and the oxygen atom of
the carbonyl group.
3.5.1.4 N-pivaloyl-Nʹ, Nʹ-dipropyl-Nʺ-phenylguanidine (a13)
The colorless block shaped crystals of a13 were grown in ethanol. The
crystallographic data was collected on the same instrument used for the analysis of a5.
The data collection and data reduction were done suing CrysAlis CCD and CrysAlis
RED. The structure was solved by direct methods and refined by full-matrix least
squares on F2 with SHELX-97. The molecular diagram for a13 is given in figure 3.4.
83
Figure 3.4: Diagram of a13 with atomic numbering scheme.
The single crystal X-ray results indicate that the guanidine core (NHC(=N)N)
in the molecule is planar and the sum of the angles around the central carbon atom is
359.9°. The values of bond lengths and angles around the central carbon atom in the
guanidine unit are given in table 3.3 which represents the Y-aromaticity in this
moiety. The steric repulsion of two propyl groups present at N11 rotates the guanidine
unit bringing the carbonyl group and guanidine unit at mutually perpendicular
positions. The importance of co-planarity for the complexation of this class of
compounds was discussed in previous pages. Due to the perpendicular arrangement of
the carbonyl group and the guanidine plane in a13, the molecule cannot behave as
bidentate ligand and hence no complexation occurs with metal ions. The important
torsion angles in a13 are given in table 3.3.
3.5.1.5 N-pivaloyl-Nʹ-(2-fluorophenyl)-Nʺ-pyridylguanidine (b7)
The rod shaped colorless crystals of b7 were grown by slow evaporation of its
methanolic solution. The crystallographic data for the compound was collected on a
Bruker Microstar generator equipped with a Kappa Nonius goniometer and platinum
135 detector. Cell refinement and data reduction were done using SAINT. The space
group was confirmed by SHELXTL. The structure was solved by the direct methods
and refined by full-matrix least-squares on F2 with SHELX-97. The molecular
diagram of b7 is given in figure 3.5.
84
a b
Figure 3.5: (a) Diagram of b7 with atomic numbering scheme. (b) Diagram of b7
showing intramolecular hydrogen bondings.
The single crystal XRD results of b7 show the planarity of the guanidine
moiety due to the strong electron delocalization in the CN3 unit. The bond lengths and
bond angles of the guanidine functionality are given in table 3.3. The C-N bond
lengths in the CN3 unit are between a double bond (C=N) and a single bond (C-N)
while the sum of bond angles is 360°. The carbonyl group and the guanidine moiety
are almost in a plane making the molecule perfect to act as bidentate ligand. The 2-
fluorophenyl group present at N2 and pyridyl ring attached at N3 are also coplanar to
the guanidine moiety creating a strong resonance in the molecule. The X-ray results
also indicate two intramolecular hydrogen bondings in the molecule. One between
N2-H and the oxygen atom of the carbonyl group while the other one between N1-H
and N4 of the pyridyl group. These intramolecular hydrogen bondings are responsible
for keeping the carbonyl group, the guanidine unit and the two aryl rings in a plane in
the solid crystal.
3.5.1.6 N-pivaloyl-Nʹ,Nʺ-bipyridylguanidine (b29)
Block shaped colorless crystals of b29 were grown in methanol. The single crystal
XRD data was collected on the same instrument used for b7. Cell refinement and data
reduction were done by the same programs. The molecular sketch of b29 is given in
figure 3.6.
85
a b
Figure 3.6: (a) Diagram of b29 with atomic numbering scheme. (b) Diagram of b29
showing intramolecular hydrogen bondings.
The X-ray diffraction studies of b29 indicate that the two pyridyl rings, the
guanidine unit and the carbonyl group are in a plane making a strong resonance in the
molecule. The important bond lengths and bond angles are given in table 3.3. The
presence of the carbonyl group and the guanidine unit in a plane make b29 suitable to
be a bidentate ligand. The two pyridyl rings are crystallographically different from
each other because one ring is closer in the space to the carbonyl group than the other.
There are two strong intramolecular hydrogen bonds in the molecule. One between
N1-H and N5 of the pyridyl group while the other one is between N3-H and the
oxygen atom of the carbonyl group. These hydrogen bonds keep the pyridyl rings in a
plane with the guanidine moiety.
86
Table 3.1: Crystal data and structure refinement parameters for a1, a4, a5, and a13.
Crystal
parameters
a1 a4 a5 a13
Empirical formula C18H21N3O C18H20N3OCl C19H23N3O2 C18H29N3O
Formula weight 295.38 329.82 325.40 303.44
Temperature (K) 100 150 296 183
Wavelength (A) 1.54178 1.54178 0.71073 0.71073
Crystal system Triclinic Monoclinic Monoclinic Orthorhombic
Space group P-1 P2(1)/c P2(1)/n P212121
Unit cell
dimensions
a(A) 9.6845(2) 9.3976(4) 11.7426(5) 9.898 (5)
b(A) 9.9027(2) 16.1570(7) 9.9844(4) 12.648 (5)
c(A) 9.9897(2) 11.5324(5) 15.9115(7) 15.126 (5)
α(°) 66.175(1) 90 90 90
β(°) 66.538(1) 104.478(2) 92.049(2) 90
γ(°) 87.681(1) 90 90 90
V (A3),
Z
795.63(3),
2
1695.44(13),
4
1864.32(14),
4
1893.6(14),
4
Density (calcd)
(Mg/m3)
1.233 1.292 1.159 1.064
Crystal size(mm3) 0.08 x 0.06 x
0.04
0.11 x 0.11 x
0.11
0.10 x 0.11 x
0.11
0.42 x 0.42 x
0.32
Index ranges -10<=h<=11
-12˂=k<=12
-12<=I<=12
-11<=h<=11
-19<=k<=17
-14<=l<=13
-14<=h<=15
-11<=k<=13
-21<=l<=12
-14<=h<=15
-19<=k<=19
-23<=l<=23
F(000) 316 696 696 664
Reflections
collected
15240 34715 20589 31051
Refinement
method
Full-matrix
least-squares
on F2
Full-matrix
least-squares
on F2
Full-matrix
least-squares
on F2
Full-matrix
least-squares
on F2
Independent
reflections
2883 3176 2367 5107
R indices (all data) 0.0456 0.0600 0.0477 0.056
Final R indices
[I˃2σ(I)]
R1 = 0.0418,
wR2=0.1393
R1 = 0.0588,
wR2=0.1694
R1 = 0.0312
wR2=0.1449
R1 = 0.029
wR2=0.134
Goodness-of-fit on
F2
1.260 1.051 1.015 0.97
Theta range for
data collection (°)
4.93 to
70.71
4.81 to 69.58 2.19 to 28.31 2.5 to 33.1
87
Table 3.2: Crystal data and structure refinement parameters for b7 and b29
Crystal parameters b7 b29
Empirical formula C17H19N4OF C16H19N5O
Formula weight 314.36 297.35
Temperature (K) 296 200
Wavelength (A) 1.54178 1.54178
Crystal system Monoclinic Monoclinic
Space group P2(1)/n P2(1)/n
Unit cell
dimensions
a(A) 10.7110(2) 6.00430(10)
b(A) 9.9954(2) 16.9550(2)
c(A) 15.2679(4) 15.2900(2)
α(°) 90 90
β(°) 91.0430(10) 92.4800(10)
γ(°) 90 90
V (A3), Z 1634.32(6),4 1555.11(4),4
Density (calcd) (Mg/m3) 1.278 1.270
Crystal size(mm3) 0.10 x 0.08 x 0.08 0.14 x 0.12 x 0.10
Index ranges -13<=h<=12
-12<=k<=12
-18<=l<=17
-7<=h<=7
-20<=k<=20
-18<=l<=18
F(000) 664 632
Total reflections 21339 20265
Refinement method Full-matrix least-
squares on F2
Full-matrix least-
squares on F2
Independent reflections 3214 [Rint = 0.045] 3032[Rint = 0.036]
R indices (all data) R1 = 0.0516
wR2 = 0.1220
R1 = 0.0464,
wR2 = 0.1154
Final R indices [I>2σ(I)] R1 = 0.0445,
wR2 = 0.1141
R1 = 0.0402,
wR2 = 0.1093
Goodness-of-fit 1.048 1.042
Theta range for data collection (°) 5.00 to 72.64 3.89 to 72.53
88
Table 3.3: Selected bond lengths, bond angles and torsion angles for guanidines
Bond lengths (A) Bond angles (°) Torsion angles (°)
a1
C5-O1
1.225(2)
C5-N1
1.369(2)
N1-C6-N2
114.26(14)
O1-C5-N1-C6
-2.6(3)
C6-N1
1.415(2)
C6-N2
1.359(2)
N1-C6-N3
122.35(15)
C5-N1-C6-N2
11.4(2)
C6-N3
1.281(2)
C7-N3
1.359(2)
N2-C6-N3
123.34(15)
C5-N1-C6-N3
-171.14(17)
C13-N2
1.416(2)
C2-C5
1.537(2)
C5-N1-C6
129.81(14)
C6-N2-C13-C14
24.1(3)
a4
O1-C5
1.225(3)
C5-N1
1.372(3)
N1-C6-N2
113.8(2)
O1-C5-N1-C6
1.3(4)
C6-N1
1.412(3)
C6-N2
1.360(3)
N1-C6-N3
123.2(2)
C5-N1-C6-N2
-13.5(3)
C6-N3
1.284(3)
C7-N3
1.408(3)
N2-C6-N3
122.8(2)
C5-N1-C6.N3
170.3(2)
C2-C5
1.530(3)
C13-N2
1.404(3)
C5-N1-C6
129.1(2)
C6-N2-C13-C14
161.7(2)
a5
C14-O2
1.2126(18)
C14-N3
1.362(2)
N1-C7-N2
124.10(15)
O2-C14-N3-C7
-1.8(3)
C7-N1
1.3557(19)
C7-N2
1.2764(19)
N1-C7-N3
114.31(14)
C14-N3-C7-N1
-1.7(3)
C7-N3
1.405(2)
N2-C8
1.417(2)
N2-C7-N3
121.58(14)
C7-N2-C8-C9
-107.0(2)
C1-N1
1.402(2)
C14-C15
1.519(2)
C7-N3-C14
131.27(14)
C7-N1-C1-C2
-0.6(3)
a13
C3-O1
1.2243 (15)
C2-N1
1.4348 (15)
N1-C2-N3
122.72 (10)
O1-C3-N1-C2
−7.40 (18)
C2-N3
1.2812 (16)
C2-N11
1.3548 (15)
N1-C2-N11
115.16 (10)
C3-N1-C2-N3
−97.25 (15)
C3-N1
1.3510 (14)
C31-N3
1.4140 (17)
N3-C2-N11
122.01 (10)
C3-N1-C2-N11
86.36 (13)
89
C11A-N11
1.4656 (16)
C11B-N11
1.4590 (17)
C3-N1-C2
121.47 (9)
C2-N3-C31-C32
−116.74 (15)
b7
C5-O1
1.2306(17)
C6-N1
1.4034(18)
N1-C6-N2
114.25(12)
O1-C5-N1-C6
1.0(2)
C6-N2
1.3613(17)
C6-N3
1.2929(18)
N1-C6-N3
123.83(12)
C5-N1-C6-N2
4.8(2)
C5-N1
1.3644(18)
C7-N3
1.3985(17)
N2-C6-N3
121.92(13)
C5-N1-C6-N3
-175.45(14)
C12-N2
1.4027(17)
C2-C5
1.526(2)
C5-N1-C6
128.79(12)
C6-N3-C7-N4
-5.5(2)
b29
C5-O1
1.2263(15)
C5-N1
1.3653(15)
N1-C6-N2
123.91(11)
O1-C5-N1-C6
0.2(2)
C6-N1
1.4017(15)
C6-N2
1.2918(15)
N1-C6-N3
114.67(10)
C5-N1-C6-N2
175.27(12)
C6-N3
1.3623(15)
C7-N3
1.4003(15)
N2-C6-N3
121.42(11)
C5-N1-C6-N3
-5.09(18)
C12-N2
1.3925(15)
C2-C5
1.5309(16)
C5-N1-C6
129.02(10)
C6-N3-C7-N4
177.02(12)
3.5.2 Single crystal X-ray studies of copper(II) complexes
The crystals of copper(II) complexes with guanidines were grown in a mixture of
chloroform and n-hexane. Suitable crystals of some complexes were analyzed by
single crystal X-ray diffraction technique. The molecular diagrams of copper(II)
complexes are given in figures 3.7 to 3.9. The crystallographic parameters are given
in table 3.4 while some important bond lengths, bond angles and torsion angles are
given in table 3.5.
3.5.2.1 Bis(N-pivaloyl-N′-(p-tolyl)-N″-phenylguanidinato)copper(II) (A6)
Blue colored block shaped crystals of A6 were grown in a mixture of chloroform and
n-hexane (30:70 v/v). The crystallographic data for the complex was collected on a
Bruker Microstar generator equipped with a Kappa Nonius goniometer and a platinum
135 detector. Cell refinement and data reduction were done using SAINT. The space
group was confirmed by XPREP routine in the program SHELXTL. The structure
90
was solved by the direct methods and refined by full-matrix least-squares on F2 with
SHELX-97. The molecular diagram of A6 is given in figure 3.7.
Figure 3.7: Diagram of A6 with atomic numbering scheme.
The XRD studies indicate that A6 crystallizes in the triclinic P-1 space group
with Z = 1. It also confirmed that the ligand to metal ratio in the complex is 2:1 and
the attachment of both ligands to the metal center is homoliptic. The geometry around
the metal center is pseudo square planar and the sum of the angles around the metal
center is 360°. The molecule is centerosymmetrical having an inversion center on the
copper atom. The Cu-N bonds are longer than the Cu-O bonds (1.990(2) A vs
1.899(2) A) but are comparable with literature reported values for guanidine
copper(II) complexes [15]. It is obvious from the torsion angles that the carbonyl
group and the guanidine moiety are still in a plane like the free ligand while the p-
tolyl group attached to N1 is almost perpendicular to the core plane of the molecule.
The phenyl ring attached to N3 is slightly deviated from the central plane of the
molecule having a torsion angle of 173.37(18)° (Table 3.5).
3.5.2.2 Bis(N-pivaloyl-N′-benzyl-N″-phenylguanidinato)copper(II) (A15)
The block shaped blue crystals of A15 were grown from the slow diffusion of hexanes
into the saturated solution of the complex in chloroform. The crystal data was
collected and solved by methods as discussed earlier. The molecular diagram of A15
is given in figure 3.8.
91
Figure 3.8: Diagram of A15 with atomic numbering scheme.
The XRD results show that the ligands are coordinated to the metal in the
same way as A6 having the pseudo square planar geometry around the metal center
and the sum of angles around the copper is 360°. The compound crystallizes in
triclinic P-1 space group with a Z =1. The metal to ligand ratio in the complex is 1:2
and both ligands are crystallographically identical. The molecule has an inversion
center Cu-N bonds are longer than the Cu-O bonds (1.9827(13) A vs 1.8969(12) A).
The torsion angles indicate that the central copper atom, the carbonyl groups and the
guanidine moieties of both ligands are in a plane while the benzyl group attached to
N3 and the phenyl ring attached to N2 are almost perpendicular to the central plane of
molecule.
3.5.2.3 Bis(N-pivaloyl-N′-(2,3-dimethylphenyl)-N″-phenylguanidinato)copper(II)
(A20)
The blue colored crystals of A20 were grown in a mixture of chloroform and hexanes
(40:60 v/v). The crystallographic data was collected on a Bruker Microstar generator
(micro source) equipped with a Helios optics, a Kappa Nonius goniometer and a
platinum 135 detector. Cell refinement and data reduction were done using SAINT.
The space group was confirmed by XPREP routine in the program SHELXTL. The
structure was solved by the direct methods and refined by full-matrix least-squares on
F2 with SHELX-97. The molecular diagram of A20 is given in figure 3.9.
92
Figure 3.9: Diagram of A20 with selected atomic numbering scheme.
The single crystal XRD results have verified that the metal to ligand ratio in
A20 is 1:2 like in the previous complexes. The crystal system is triclinic having a
space group of P-1 with Z = 1. The geometry around the copper atom is pseudo
square planar having an inversion center on copper making both ligands
crystallographically identical. Again, the ligand is bidentate coordinating through a
nitrogen and an oxygen atom. The Cu-O bond length is 1.904(3) A while the Cu-N2
bond length is 1.989(3) A. The phenyl ring attached to N3 is almost in a plane with
the square planar core of the complex while the 2,3-dimethylphenyl group attached to
N2 is perpendicular to it.
93
Table 3.4: Crystal data and structure refinement parameters for A6, A15 and A20.
Crystal parameters A6 A15 A20
Empirical formula C38H44CuN6O2 C38H44CuN6O2 C40H46CuN6O2
Formula weight 680.33 680.33 706.37
Temperature (K) 150 100 150
Wavelength (A) 1.54178 1.54178 1.54178
Crystal system Triclinic Triclinic Triclinic
Space group P-1 P-1 P-1
Unit cell
dimensions
a(A) 8.3699(3) 6.2096(1) 8.4578(3)
b(A) 9.1922(3) 10.4567(2) 9.6925(4)
c(A) 13.1967(4) 13.7729(3) 11.6549(4)
α(°) 108.829(1) 82.180(1) 94.458(2)
β(°) 94.377(2) 87.212(1) 99.7540(10)
γ(°) 110.757(2) 82.840(1) 102.993(2)
V (A3), Z 877.51(5),1 878.62(3),1 910.82(6),1
Density (calcd)
(Mg/m3)
1.287 1.286 1.288
Crystal size(mm3) 0.18 x 0.15 x 0.08 0.08 x 0.06 x 0.02 0.14 x 0.12 x 0.08
Index ranges -10<=h<=7
-11<=k<=11
-15<=l<=15
-7<=h<=7
-12<=k<=12
-16<=l<=16
-10<=h<=10
-10<=k<=11
-14<=l<=14
F(000) 359 359 373
Total reflections 17851 25871 8227
Refinement method Full-matrix least-
squares on F2
Full-matrix least-
squares on F2
Full-matrix least-
squares on F2
Independent
reflections
3224 [Rint =
0.040]
3090[Rint =
0.030]
1897[Rint =
0.0394]
R indices (all data) R1 = 0.0596,
wR2 = 0.1709
R1 = 0.0389,
wR2 = 0.1034
R1 = 0.0676,
wR2 = 0.2349
Final R indices
[I>2σ(I)]
R1 = 0.0580,
wR2 = 0.1688
R1 = 0.0374,
wR2 = 0.1020
R1 = 0.0671,
wR2 = 0.2334
Goodness-of-fit 1.077 1.061 1.259
Theta range for data
collection (°)
5.37 to 69.68 3.24 to 71.12 5.74 to 69.55
94
Table 3.5: Selected bond lengths, bond angles and torsion angles for Cu(II)
complexes
Bond lengths (A) Bond angles (°) Torsion angles (°)
A6
Cu1-N1
1.990(2)
Cu1-O1
1.899(2)
N1-Cu1-O1
90.19(9)
Cu1-O1-C5-N2
-0.4(4)
C5-O1
1.269(4)
C5-N2
1.318(4)
N1-Cu1-O1*
89.81(9)
Cu1-N1-C6-C7
-88.8(3)
C13-N2
1.363(3)
C13-N1
1.323(4)
Cu1-O1-C5
128.04(18)
Cu1-N1-C13-N3
-173.37(18)
A15
Cu1-O1
1.8969(12)
Cu1-N2
1.9827(13)
N2-Cu1-O1
90.61(6)
Cu1-O1-C5-N1
0.1(3)
C5-O1
1.276(2)
C5-N1
1.309(2)
N2-Cu1-O1*
89.39(6)
Cu1-N2-C6-N3
179.12(11)
C6-N1
1.360(2)
C6-N2
1.326(2)
Cu1-O1-C5
127.50(11)
Cu1-N2-C14-C15
-90.26(17)
A20
Cu-O
1.904(3)
Cu-N2
1.989(3)
N2-Cu-O
89.93(15)
Cu-O-C1-N1
0.32(4)
C1-O
1.282(5)
C1-N1
1.302(5)
N2-Cu-O*
90.07(15)
Cu-N2-C6-N3
179.54(12)
C6-N1
1.347(6)
C6-N2
1.317(5)
Cu-O-C1
127.3(3)
Cu-N2-C7-C8
-88.79(13)
3.5.3 Single crystal X-ray studies of bis(N-pivaloyl-Nʹ,Nʺ-
diphenylguanidinato)nickel(II) (Nia1)
A number of nickel(II) complexes was synthesized but unfortunately they were
insoluble in common solvents and hence their crystals were not grown properly.
Luckily, bis(N-pivaloyl-Nʹ,Nʺ-diphenylguanidinato)nickel(II) (Nia1) was a crystalline
solid having pink color. Some crystals of suitable size were separated from the
product and were analyzed by the single crystal X-ray diffraction method. The
molecular diagram of Nia1 is given in figure 3.10. The crystallographic parameters
are given in table 3.6 while some important bond lengths, bond angles and torsion
angles are given in table 3.7.
95
Figure 3.10: Diagram of Nia1 with atomic numbering scheme.
Bis(N-pivaloyl-Nʹ,Nʺ-diphenylguanidinato)nickel(II) crystallized in the
triclinic P-1 space group with Z = 1. The metal to ligand ratio in the complex is 1:2
which is complimentary to the elemental analysis. The ligand is bidentate,
coordinating through the oxygen atom of the carbonyl group and a de-protonated
nitrogen of the guanidine unit. The complex is pseudo square planar with a sum of
angles around the nickel center of 360°. The molecule has an inversion center located
on the nickel atom. The two ligands are crystallographically identical. The Ni-O bond
length is 1.8474(12) A while the Ni-N1 bond length is 1.9129(15) A. These bond
lengths are shorter than in the copper(II) complexes already discussed. It is obvious
from the single crystal XRD results that the phenyl ring attached to N3 is almost
coplanar to the complex center while the plane of the phenyl ring attached to N1 is
perpendicular.
Table 3.6: Crystal data and structure refinement parameters for Nia1
Crystal parameters
Empirical formula C36H40N6NiO2 Formula weight 647.45
Temperature (K) 150 Wavelength (A) 1.54178
Crystal system Triclinic Space group P-1
Unit cell
dimensions
a(A) 8.1365(1) V (A3) 806.341(19)
b(A) 9.2929(1) Z 1
96
c(A) 11.7562(2) Density (calcd)
(Mg/m3)
1.333
α(°) 95.463(1) Index ranges -9<=h<=9
-11<=k<=11
-14<=l<=14
β(°) 101.452(1)
γ(°) 109.894(1)
Crystal size(mm3) 0.08 x 0.06 x 0.04 F(000) 342
Total reflections 47122 Goodness-of-fit 1.055
Refinement
method
Full-matrix least-
squares on F2
R indices (all
data)
R1 = 0.0408,
wR2 = 0.1073
Independent
reflections
3007 [Rint =
0.020]
Final R indices
[I>2σ(I)]
R1 = 0.0399,
wR2 = 0.1066
Theta range for
data collection (°)
5.14 to 71.08
Table 3.7: Selected bond lengths, bond angles and torsion angles for Nia1
Bond lengths (A)
Bond angles (°) Torsion angles (°)
Ni1-O1
1.8474(12)
Ni1-N1
1.9129(15)
N1-Ni1-O1
91.01(6)
Ni1-O1-C5-N2
0.2(3)
C5-O1
1.276(2)
C5-N2
1.307(2)
N1-Ni1-O1*
88.99(6)
Ni1-N1-C6-N3
172.60(13)
C6-N2
1.359(2)
C6-N1
1.325(2)
Ni1-O1-C5
127.95(12)
Ni1-N1-C13-C14
-92.78(18)
References
1. Murtaza, G.; Rauf, M.K.; Badshah, A.; Ebihara, M.; Said, M.; Gielen, M.; De
Vos, D.; Dilshad, E.; Mirza, B., Eur. J. Med. Chem. 2012, 48, 26. (b) Fregona, D.;
Giovagnini, L.; Ronconi, L.; Marzano, C.; Treevisan, A.; Sitran S.; Bordin, B., J.
Inorg. Biochem. 2003, 93, 181.
2. Atta-ur-Rehman Nuclear Magnatic Resonance Spectroscopy, National Academy
of Higher Education, Pakistan, 1989, pp 23.
97
3. Cunha, S.; Rodrigues, M.T.; De Silva, C.C.; Napolitano, H.B.; Vencato, I.;
Laricci, C., Tetrahedron 2005, 61, 10536.
4. Kolinowski, H.O.; Berger, S.; Brown, S., 13C NMR Spectroscopy, Thieme-Verlag,
Stuttgart, Germany, 1984.
5. Murtaza, G.; Badshah, A.; Said, M.; Khan, H.; Khan, A.; Khan, S.; Siddiq, S.;
Choudhary, M.I.; Boudreau, J.; Fontaine, F-G., Dalton Trans. 2011, 40, 9202.
6. (a) Sheldrick, G.M., Acta Cryst. 2008, A64, 112. (b) Altomare, A.; Burla, M.C.;
Camalli, M.; Cascarano, G.L.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A.G.G.;
Polidori, G.; Spagna, R., J. Appl. Cryst. 1999, 32, 115.
7. SAINT, Release 6.06; Integration Software for Single Crystal Data; Bruker AXS
Inc.: Madison, WI, 1999.
8. XPREP, Release 5.10; X-ray Data Preparation and Reciprocal Space Exploration
Program; Bruker AXS Inc.: Madison, WI, 1997.
9. SHELXTL, Release 5.10; The Complete Software Package for Single Crystal
Structure Determination; Bruker AXS Inc.: Madison, WI, 1997.
10. (a) Sheldrick, G.M. SHELXS97, Program for the Solution of Crystal Structures;
Univ. of Gottingen, Germany, 1997. (b) Sheldrick, G.M. SHELXL97, Program for
the Refinement of Crystal Structures; University of Gottingen, Germany, 1997.
11. Allen, F.H.; Kennard, O.; Watson, D.G.; Brammer, L.; Orpen, A.G., J. Chem. Soc.
Perkin Trans. II, 1987, S1.
12. Faraglia, G.; Fregona, D.; Sitranb, S.; Giovagninia, L.; Marzano, C.; Baccichetti,
F.; Casellato, U.; Graziani, R., J. Inorg. Biochem. 2001, 83, 31.
13. CrysAlis CCD, Oxford Diffraction Ltd., Version 1.171.31.8
14. CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.31.8
15. (a) Schroder, U.; Beyer, L.; Richter, R.; Angulo-Cornejo, J.; Castillo-Montoya,
M.; Lino-Pacheco, M., Inorg. Chim. Acta 2003, 353, 59. (b) Beyer, L.; Richter,
R.; Wolf, R.; Zaumseil, J.; Lino-Pacheco, M.; Angulo-Cornejo, J.; Inorg. Chem.
Comm. 1999, 2, 184. (c) Begley, M.J.; Hubberstey, P.; Moore, C.H.M., J. Chem.
Res. 1986, 5, 172. (d) Tomas, A.; Viossat, B.; Charlot, M.F., Girerd, J.J.; Huy,
D.N., Inorg. Chim. Acta 2005, 358, 3253.
98
Chapter-4
Biological Screening
4.1 Biological assay
The chemists are always interested in the exploration of novel means to facilitate
human life. The development of new pharmaceuticals, to overcome human medical
problems and enhance health facilities, is an imperative field of chemistry. Substituted
guanidines are known for their broad spectrum of physiological activities including
anticancer, antimicrobial, antileishmanial, antihypertensive and antiviral activities. On
the other hand, copper being an essential metal for the body and non-toxic in
controlled quantity, is implicated in many diseases [1]. The synthesized guanidines
and copper(II) complexes were scrutinized for their anticancer, antioxidant, antifungal
and antibiotic activities as discussed below.
4.2 Cytotoxicity
The cytotoxic activity of metals is due to the generation of reactive oxygen species
(ROS) by redox-active metal ions which damage the DNA and other biomolecules via
Haber-Weiss or Fenton-like reactions [2]. Metal-based drugs are being used
effectively for the treatment of cancer as the metal ions are capable of binding stereo-
specifically to nucleic acids [3]. There are many organic-metal compounds which
actively and specifically inhibit the chymotrypsin like activity of the proteasome in
vitro and in human tumor-cell cultures [4]. The anticancer activity of certain platinum
and palladium complexes is promising but these metals are nonessential to the human
body and there is no effective mechanism for their removal from the body as for the
other metals like copper and iron. Due to the selective permeability of cancer cell
membranes to copper compounds, copper accumulates in tumors, as observed in
many types of human cancers [5]. The compounds containing guanidine are reported
as inhibitor of urokinase that plays a vital role in tumor metastasis and is implicated in
a large number of malignancies [6]. The different tests applied to determine the
cytotoxicity of synthesized compounds are as follows.
4.2.1 Brine shrimps (Artemia salina) lethality assay
Cytotoxicity was studied by the brine-shrimp lethality assay using a literature reported
method [7] with little modifications.
99
i) Preparation of the culture
Brine-shrimp (Artemia salina) eggs were hatched in artificial sea water (sea salt 38 g/L
in dist. H2O) at room temperature (22-28 °C).
ii) Preparation of stock solutions
The stock solutions of test compounds were prepared in DMSO (12 mg/mL).
iii) Lethality test
After two days, saline water with brine-shrimp (10 shrimps per vial) was added to
vials containing sea water and the final concentration of the test compound was
adjusted to 10, 100, and 1000 µg/mL. After 24 hours, the number of surviving
shrimps was counted and ED50 values determined by analysing the data with a biostat
2009 computer programme (Probit analysis).
Table 4.1: Brine shrimps lethality assay for selected guanidines and their copper(II)
complexes
Ligands ED50 ppm Complexes ED50 ppm
a1 210.41 A1 178.49
a2 78.34 A2 03.37
a3 128.75 A3 93.92
a4 140.74 A4 62.25
a5 103.81 A5 98.72
a6 -- A6 106.07
a10 380.27 A10 363.95
a15 154.38 A15 174.74
a16 261.52 A16 556.51
a17 145.20 A17 152.40
a19 320.27 A19 205.35
a20 172.39 A20 142.73
The ED50 values for some selected guanidines and their Cu(II) complexes are given in
table 4.1. The results indicated that most of the compounds have high cytotoxic
activities. Among all the free ligands tested, a2 is the most cytotoxic with ED50 value
78.34 ppm, while among the Cu(II) complexes, A2 is the most active (ED50 value
3.37 ppm). The rest of the compounds have shown the activities with ED50 ranging
from 62.25- 556.51 ppm. It is evident from the results that the cytotoxicity of active
100
compounds is concentration dependent. Among the tested compounds those having
chloro-aryl substituents have lower ED50 values than compounds having simple aryl
and alkyl substituents. The results also indicated that in most cases copper(II)
complexes are more cytotoxic than free ligands.
4.2.2 Potato disc anti-tumor assay
Potato disc anti-tumor assay (Crown gall tumor inhibition assay) was conducted to
test the cytotoxic behaviour of the synthesized compounds. Agrobacterium
tumefaciens (strain AT10) by its tumor inducing plasmids induces the plant tumor
known as crown gall tumor.
The protocol reported by McLaughlin et al. was followed for the estimation of
potato disc anti-tumor assay [8] which includes the following steps.
i) Preparation of bacterial culture
Luria broth 2.5% was prepared by dissolving 2.5 g of LB (Luria broth) in 100 mL of
distilled water, autoclaved and then added 20 µL of rifampicin stock solution (50
mg/mL) to make the final volume having a concentration of rifampicin 10 µg/mL. A
single colony from the culture plate of Agrobacterium tumefaciens (AT10) was
inoculated in it and allowed to grow for 48 hours at 28 °C in a shaking incubator.
ii) Preparation of stock solutions
All samples for assay were prepared by dissolving 10 mg of the samples compound in
1 mL of DMSO to prepare 10,000 μg/mL stock solutions. Work solutions of 5000
μg/mL were prepared in DMSO from already prepared stock solutions.
iii) Preparation of inoculums
In order to attain the 500 μg/mL final concentrations of test sample in the inoculums,
1500 µL of the inoculums were prepared by taking 150 µL of the test sample stock
solution (5000 μg/mL) in each of three autoclaved eppendorfs. Then 750 µL of the
autoclaved distilled water and 600 µl of bacterial culture were added to each
eppendorf.
iv) Preparation of control solutions
Three controls were used in the assay:
a. Positive control; prepared by taking 150 µL of DMSO in autoclaved eppendorfs
and then adding 1350 µL of autoclaved distilled water in it.
101
b. Negative control; prepared by taking 150 µL of DMSO in autoclaved eppendorfs,
then adding 750 µL of autoclaved distilled water and 600 µL of bacterial culture
in it.
c. Blank potato discs used as control;
All the solutions were prepared in a laminar flow hood by considering all
precautionary measures to avoid contamination.
v) Preparation of agar plates
The agar solution (1.5% in distilled water) was prepared, autoclaved, poured in
autoclaved petri plates and allowed to solidify. 25 mL of the agar solution was needed
for each petri plate. The petri plates were prepared in triplicate for each concentration
of test sample and control.
vi) Preparation of potato discs
Red skinned potatoes were soaked in a 0.1% mercuric chloride solution for 10
minutes and then taken out with the help of a large size sterilized forceps in a large
petri plate (autoclaved). Cylinders were made with the help of a sterilized borer (8
mm), washed with autoclaved distilled water and cut 1 cm on both ends with the help
of a sterilized blade. Potato discs of a thickness of 5 mm were cut from these
cylinders. Discs were washed with autoclaved distilled water and placed on solidified
agar plates (12 discs per plate). 50 µL of the inoculum was added on the surface of
each disc of respective concentration as well as controls. Inoculums were allowed to
diffuse for 10-20 min. The edge of each petri plate was sealed with para film strips to
make air tight and prevent moisture loss during the incubation period. A dish level
was kept all the time to keep the inoculums on the top of the discs. Petri plates were
placed in the dark at 28 °C for 21 days.
vii) Staining procedure
Discs were covered with Lugol’s solution (10% KI and 5% I2 in distilled water) for
staining purpose. After 30 min discs were observed under a dissecting microscope
with a side illumination of light. Distained portions of the discs were tumors. Number
of tumors per disc was counted and the percentage of inhibition for each
concentration was determined as follows:
%age inhibition = 100 - (average number of tumors of sample) × 100
(average number of tumors of –ve control)
102
Table 4.2: Potato disc antitumor assay of selected guanidines and their copper(II)
complexes
Compound Average
number of
tumors
Percentage
inhibition of
tumors
Compound Average
number of
tumors
Percentage
inhibition
of tumors
b1 3 60 B1 2 73
b2 3 60 B2 1 87
b3 4.5 40 B3 3 60
b4 4 47 B4 3 60
b5 4 47 B5 2 73
b6 4 47 B6 1.5 80
b7 3 60 B7 2 73
b8 3.5 53 B8 2 73
b9 --- --- B9 3 60
b10 4 47 B10 2 73
b11 3 60 B11 2 73
b12 4.5 40 B12 2 73
b29 4 47 B29 3 60
Vincristine 0.0 ± 0.0 100 AT10 7.5
BLANK 0 100
Note: i) More than 20% inhibition was considered significant
ii) Data represents mean value of 3 replicates
The percentage inhibition of tumor by some selected test compounds is given
in table 4.2. The results indicated that most of the compounds have shown good to
excellent anti-tumor activity. Among all the compounds tested, B2 has shown the
highest activity, 87% compared to the standard vincristine taken as 100%. It is
observed that complexes are more active as compared to free guanidines which may
be attributed to the presence of Cu(II) as well as to the increased lipophilicity of
complexes.
103
4.3 Anti-oxidant study
The anti-oxidant behaviour of synthesized compounds was investigated by a reported
method of Brand-Williams et al. [9] with few modifications. For the modified
procedure, stock solutions of DPPH and samples were prepared in 80% methanol.
Using 80% methanol had the advantage of lower evaporation losses. Test samples
were prepared by mixing a calculated volume of samples, stock solutions and DPPH
stock solution. The final concentration of samples in samples tubes was kept in the
range of 14-1000 μg while a fixed amount of DPPH was added to all samples in such
a way that the mixture had an absorbance around 0.99 at 517 nm at the time of
mixing. Samples were prepared in triplicate for each concentration used and at least
seven different concentrations were used for each sample. The sample tubes were
covered with aluminium foils and left in the incubator at 37 °C. After 1, 24, 48 and
72 hours, the absorbance at 517 nm was recorded by UV-Vis spectrophotometer.
DPPH solution was used as a control. The scavenging activity was estimated which is
based on the percentage of DPPH radical scavenged, using the following equation:
Scavenging effect (%) = (control absorbance – sample absorbance)
× 100
(control absorbance)
1000 50
025
012
562
.5 28 14
DPP
H
0
10
20
30
40
501hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
1000 50
025
012
562
.5 28 14
DPP
H
0
10
20
30
40
501hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
(b1) ( B1 )
1000 50
025
012
562
.5 28 14
DPP
H
0
20
40
601hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
1000 50
025
012
562
.5 28 14
DPP
H
0
5
10
15
20
251hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
(b2) (B2)
Figure 4.1: Graphical presentation showing the percent scavenging of DPPH by some
guanidines and their copper(II) complexes (continued......).
104
1000
.0
500.
0
250.
0
125.
062
.528
.014
.0
DPP
H
0
20
40
601hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
(b4)
1000
.0
500.
0
250.
0
125.
062
.528
.014
.0
DPP
H
0
20
40
60
80
1001hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
1000 50
025
012
562
.5 28 14
DPP
H
0
10
20
30
40
501hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
(b6) (B6)
1000 50
025
012
562
.5 28 14
DPP
H
0
20
40
60
801hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
1000 50
025
012
562
.5 28 14
DPP
H
0
20
40
60
801hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
(b7) (B7)
1000 50
025
012
562
.5 28 14
DPP
H
0
20
40
60
801hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
1000 50
025
012
562
.5 28 14
DPP
H
0
20
40
60
801hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
(b10) (B10)
Figure 4.1: Graphical presentation showing the percent scavenging of DPPH by some
guanidines and their copper(II) complexes (continued......).
105
1000 50
025
012
562
.5 28 14
DPP
H
0
20
40
60
801hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
1000 50
025
012
562
.5 28 14
DPP
H
0
10
20
30
40
501hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
(b12) (B12)
1000 50
025
012
562
.5 28 14
DPP
H
0
20
40
60
801hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
1000 50
025
012
562
.5 28 14
DPP
H
0
20
40
60
801hr
24hr
48hr
72hr
Concentration(ug/mL)
Perc
en
t In
hib
itio
n
(b13) (b14)
Figure 4.1: Graphical presentation showing the percent scavenging of DPPH by some
guanidines and their copper(II) complexes at various concentrations and
time intervals.
The percent scavenging of DPPH by some selected guanidines and their
copper(II) complexes is shown in figure 4.1. The results indicate that the scavenging
of DPPH by the tested compounds is a time dependent and relatively slow process. It
is also obvious from the results that the antioxidant property of free guanidines is
suppressed by the complexation with copper(II). The percent scavenging of DPPH by
guanidines can also be correlated to the substituent attached at the Nʹ position.
Generally, the presence of an electron donor substituent such as an alkyl group
enhances the antioxidant property of guanidine while an electron withdrawing group
suppresses the DPPH scavenging ability. Few exceptions to this general trend are b6
and b7.
4.4 Antifungal activity
The selected synthesized guanidines and their copper(II) complexes were investigated
for their antifungal activity against four fungal strains: Aspergillus niger, Fusarium
106
solanai, Aspergillus fumagatus and Aspergillus flaves. The susceptibility test was
performed by using the agar tube dilution method [10] with some modifications [11]
using terbinafine as reference drug. Scew caped test tubes containing a sabouraud
dextrose agar (SDA) medium (4 mL) were autoclaved at 121 °C for 15 minutes.
Tubes were allowed to cool at 50 °C and non-solidified SDA was loaded with 66.6 µL
of the test compound from the stock solution (12 mg/mL in DMSO) to make final
concentration of 200 µg/mL. Tubes were then allowed to solidify in a slanting
position at room temperature. Each tube was inoculated with a 4 mm diameter piece
of inoculum from seven days old fungal culture. The media supplemented with
DMSO and terbinafine (200 µg/mL) were used as negative and positive control. The
tubes were incubated at 28 °C for 7 days and the growth in the media was determined
by measuring the linear growth (mm). Growth inhibition was calculated with the
reference to growth in vehicle control as shown in the equation.
Percentage growth inhibition = 100 -Linear growth in test (mm)
Linear growth in control (mm) ×100
Table 4.3: Antifungal activity of selected guanidines and their copper(II) complexes
Compound Percentage inhibition in linear growth (in mm)
A. Niger F. Solanai A. Fumigatus A. Flaves
a1 32.29 40.31 20.67 25.02
a2 39.74 38.71 50.12 41.47
a3 29.56 14.80 31.82 42.18
a6 32.4 26.14 43.23 37.61
a10 25.78 20.72 37.01 34.70
a15 21.32 17.26 31.65 19.14
a16 38.71 19.45 11.31 41.73
a17 ---- 32.83 39.28 30.51
a20 28.39 20.42 31.40 37.76
a28 11.24 13.61 39.31 16.83
A1 46.78 62.96 24.75 23.21
A2 46.78 35.18 52.37 40.60
A3 24.77 35.18 55.44 45.53
A6 17.43 11.85 57.42 20.53
A10 22.01 22.77 64.35 37.50
107
Compound Percentage inhibition in linear growth (in mm)
A. Niger F. Solanai A. Fumigatus A. Flaves
A15 26.60 7.40 41.58 22.32
A16 41.28 6.48 51.48 39.28
A17 15.59 72.22 20.79 39.28
A20 27.33 25.92 50.49 30.35
A28 18.25 32.40 64.35 32.14
Terbinafine 100 100 100 100
Linear
growth in –
ve control
54.5 54 50.5 56
The results are summarized in table 4.3. Activity was measured on the basis of
percent growth inhibition. More than 70% inhibition was considered as significant,
60-70% as good, 50-60% as moderate and below 50% as insignificant activity. The
complexes A3, A10 and A28 showed good activity against A. Fumigatus while A1
has good activity against F. Solanai. The over all results indicated that guanidine
ligands have moderate/insignificant antifungal activities. In most cases, the copper(II)
complexes are slightly more active as compared to the free ligands.
4.5 Antibacterial activity
The synthesized compounds were tested against six bacterial strains; two gram-
positive [Micrococcus luteus (ATCC10240) and Staphylococcus aureus
(ATCC6538)] and four gram-negative [Escherichia coli (ATCC15224),
Enterobactor aerogenes (ATCC13048), Bordetella bronchiseptica (ATCC4617) and
Klebsiella pneumoniae (MTCC618)]. The agar well-diffusion method was used for
the determination of antibacterial activity. Broth culture (0.75 mL) containing ca. 106
colony forming units (CFU) per mL of the test strain was added to 75 mL of t h e
n u t r i e n t a g a r m e d i u m a t 4 5 ° C , m i x e d w e l l , a n d t h e n p o u r e d
i n t o a 1 4 c m diameter sterile petri plate. The media was allowed to solidify and 8
mm wells were dug with a sterile metallic borer. Then a DMSO solution of test
samples (100 µL) at 1 mg/mL was added to the respective wells. DMSO served as
negative control, and the standard antibacterial drug cefixime (1 mg/mL) was used as
positive control. Triplicate plates of each bacterial strain were prepared which were
incubated aerobically at 37 °C for 24 hours. The activity was determined by
108
measuring the diameter of zone showing complete inhibition (mm).
Table 4.4: Antibactrial activity of selected guanidines and their copper(II) complexes
Comp
ound
Mean zone of inhibition (mm) S.
Aureus (ATCC 6538)
K.
Pneumoniae (MTCC618)
M.
Luteus (ATCC10240)
E.
Aerogenase (ATCC13048)
E.
Coli (ATCC5224)
B.
Brochiseptica (ATCC4617)
b2 12 --- 15 --- 15 16
b3 --- 9 --- --- --- ---
b4 --- --- --- --- --- ---
b6 --- --- --- --- 18 ---
b8 12 --- 12 --- 18 ---
b9 15 --- 15 --- --- 13
b10 15 --- 20 --- 13 13
b11 13 --- 14 12 12 ---
b12 15 13 15 14 17 15
b13 12 12 12 --- 16 ---
b14 12 --- 12 9 --- ---
b29 --- --- --- --- --- ---
B2 9 10 12 --- 13 10
B3 --- --- 11 --- --- ---
B4 --- --- --- --- --- ---
B6 --- --- --- 9 --- ---
B8 --- --- --- --- --- 9
B9 12 --- 10 12 10 ---
B10 --- --- --- --- 16 ---
B11 15 9 --- 17 14 9
B12 10 --- 13 15 11 16
B29 --- --- --- --- --- ---
Cefi
xime 33.3 32.6 51 36 41 34.3
Note: Mean zone of inhibition less than 9 mm is considered as no activity represented
as “----”.
109
The results for antibacterial assay for some selected guanidines and their
copper(II) complexes are given in table 4.4. The antibacterial activity is measured on
the basis of zone of inhibition compared with standard drug Cefixime. The activity of
compounds having a zone of inhibition less than 8 mm is considered as nil. The
results indicate that the overall activity of tested guanidines is non-significant which is
further suppressed by the complexation with copper(II). The decrease in antibacterial
activity of the complexes may be due to non polar nature of the synthesized
complexes which do not interact with the bacterial cell membrane. Among the tested
compounds b6 and b8 have moderate activity against E. Coli while b10 shows
activity against M. Luteus.
110
References
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111
Conclusions
1. Two series of pivaloyl substituted guanidines (containing 57 compounds) were
synthesized and fully characterized by elemental analysis, IR spectroscopy,
multinuclear NMR (1H, 13C) and single crystal X-ray diffraction techniques.
2. Generally, the crystalline packing of synthesized guanidines has been
stabilized by intermolecular as well as intramolecular H-bonding.
3. Copper(II) complexes of these guanidines were also synthesized and
characterized. Coordination chemistry of pivaloyl substituted guanidines
depends on the substituents attached to the CN3 moiety, the inductive effect
and the steric hindrance created by the substituents.
4. Pivaloylguanidines act as bidentate chelating ligands which coordinate with
Cu(II) through the oxygen atom of the carbonyl group and the nitrogen atoms
of the guanidine moiety.
5. The geometry around the metal center is square planar with a metal-ligand
ratio of 1:2.
6. The anticancer assay using the potato disc method has shown that guanidines
have significant activities which is further enhanced by complexation with
Cu(II).
7. Antifungal and antibiotic activities of synthesized guanidines are insignificant.
The antibacterial properties of the free ligands are further suppressed by
complexation.
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Future plans
1. As the free ligands and their Cu(II) complexes show significant activities
against potato tumors, the future plan is to test these compounds on other cell
lines specially human cell lines for their anticancer behavior.
2. It is in our pipeline to synthesize complexes of pivaloyl substituted guanidines
with other transition metals and screen their biological activities.
3. We are interested to find out the anti-oxidant behavior of synthesized
compounds on other vitro and vivo models to decide whether this class of
compounds can be used as anti-oxidant or not.
4. In future we are planning to study the effects of the synthesized compounds on
various body tissues to take further steps to use them as drugs especially
against cancer.
5. As the tested synthesized compounds have shown good antifungal activities,
so we are interested to screen all the compounds for their antifungal behavior.