research article open access thermal decomposition of …iii 3.3 ii 0.7 [feii(cn) 6] 3.3 ·13h 2o...

Traacutevniacuteček et al Chemistry Central Journal 2013 728httpjournalchemistrycentralcomcontent7128

RESEARCH ARTICLE Open Access

Thermal decomposition of [Co(en)3][Fe(CN)6]∙2H2O Topotactic dehydration process valenceand spin exchange mechanism elucidationZdeněk Traacutevniacuteček1 Radek Zbořil2 Miroslava Matikovaacute-Maľarovaacute1 Bohuslav Drahoš1 and Juraj Černaacutek3

Abstract

Background The Prussian blue analogues represent well-known and extensively studied group of coordinationspecies which has many remarkable applications due to their ion-exchange electron transfer or magneticproperties Among them Co-Fe Prussian blue analogues have been extensively studied due to the photoinducedmagnetization Surprisingly their suitability as precursors for solid-state synthesis of magnetic nanoparticles isalmost unexploredIn this paper the mechanism of thermal decomposition of [Co(en)3][Fe(CN)6] ∙ 2H2O (1a) is elucidated including thetopotactic dehydration valence and spins exchange mechanisms suggestion and the formation of a mixture ofCoFe2O4-Co3O4 (31) as final products of thermal degradation

Results The course of thermal decomposition of 1a in air atmosphere up to 600degC was monitored by TGDSCtechniques 57Fe Moumlssbauer and IR spectroscopy As first the topotactic dehydration of 1a to the hemihydrate [Co(en)3][Fe(CN)6] ∙ 12H2O (1b) occurred with preserving the single-crystal character as was confirmed by the X-raydiffraction analysis The consequent thermal decomposition proceeded in further four stages includingintermediates varying in valence and spin states of both transition metal ions in their structures ie [FeII(en)2(μ-NC)CoIII(CN)4] Fe

III(NH2CH2CH3)2(μ-NC)2CoII(CN)3] and FeIII[CoII(CN)5] which were suggested mainly from 57FeMoumlssbauer IR spectral and elemental analyses data Thermal decomposition was completed at 400degC whensuperparamagnetic phases of CoFe2O4 and Co3O4 in the molar ratio of 31 were formed During furthertemperature increase (450 and 600degC) the ongoing crystallization process gave a new ferromagnetic phaseattributed to the CoFe2O4-Co3O4 nanocomposite particles Their formation was confirmed by XRD and TEManalyses In-field (5 K 5 T) Moumlssbauer spectrum revealed canting of Fe(III) spin in almost fully inverse spinelstructure of CoFe2O4

Conclusions It has been found that the thermal decomposition of [Co(en)3][Fe(CN)6] ∙ 2H2O in air atmosphere is agradual multiple process accompanied by the formation of intermediates with different compositionstereochemistry oxidation as well as spin states of both the central transition metals The decomposition is finishedabove 400degC and the ongoing heating to 600degC results in the formation of CoFe2O4-Co3O4 nanocomposite particlesas the final decomposition product

Keywords Hexacyanidoferrate Crystal structure Thermal behavior Moumlssbauer spectroscopy Topotacticdehydration Nanocomposite particles CoFe2O4

Correspondence zdenektravnicekupolcz1Regional Centre of Advanced Technologies and Materials amp Department ofInorganic Chemistry Palackyacute University Tř 17 listopadu 12 OlomoucCZ-77146 Czech RepublicFull list of author information is available at the end of the article

copy 2013 Travnicek et al licensee Chemistry Central Ltd This is an Open Access article distributed under the terms of theCreative Commons Attribution License (httpcreativecommonsorglicensesby20) which permits unrestricted usedistribution and reproduction in any medium provided the original work is properly cited

Traacutevniacuteček et al Chemistry Central Journal 2013 728 Page 2 of 18httpjournalchemistrycentralcomcontent7128

BackgroundTransition metal hexacyanido complexes represent anenormous and well-known group of coordination spe-cies The Prussian blue with the idealized formula Fe4[Fe(CN)6]3 middot nH2O is one of the oldest examples of ahexacyanido complex combining interesting structuralfeatures and magnetic properties Therefore manyPrussian blue analogues [1] eg MxA[B(CN)6]z middot nH2O(M is alkali metal A and B are different divalenttriva-lent transition metals x le 1 z le 1 if z lt 1 B-sites are frac-tionally occupied and B-vacancies are present) have beenextensively studied due to their sorption ion-exchangeelectron transfer or magnetic properties and in recentyears many applications using PBAs usually in form ofthin films or nanoparticles have been developed [23]The reversible intercalation of alkali metal cations due

to the zeolite-like structure of PBAs [4] has beenemployed in still active development of the selective ad-sorbent of 137Cs from radioactive waste waters [5] or morerecently in construction of a new active electrode materialfor Li-ion batteries (AxMny[Fe(CN)6] where A = K Rbx lt 1 1 lt y lt 15) [6] The electrochemical coating ofelectrodes with thin film of PBAs or deposition withcoordinated PBAs nanoparticles [278] gave rise a largenumber of amperometric and potentiometric sensors fornon-electroactive ions or H2O2 [39] electrochromicsensors [10] or biosensors [11] The electrochromic orthermochromic behavior of electrochemically preparedPBAs thin films was further applied in the construction ofdifferent devices including electrochromic displays andpattering devices thermal probes or photoelectrochem-icalphotocatalytical solar energy convertors [12]PBAs also represent an enormous and important

group of molecular magnets [113-15] which play im-portant roles in many applications mainly in molecularelectronics and magneticelectronic devices [1617] Dur-ing the experimental race to enhance the Curietemperatures of molecular magnets based on PBAs thesystems incorporating V(II) gave the most promisingresults and KV[Cr(CN)6]middot2H2O was found to possess thehighest Tc even above the boiling point of water (376 K)[18] This invention of room temperature molecule-based magnets opens interesting applications as mag-netic switches oscillators or magneto-optical datastorage devices The cyanido-bridged networks servingas a platform for the preparation of coordinationnanoparticles based on Prussian blue has also beenemployed for the controllingtuning of magnetism bytemperature (eg AI[MIIMIII(CN)6] A = alkali metal ion)[2] or light irradiation (with a general formula of AxCoy[Fe(CN)6]z middot nH2O x y z are independent) [8]An important feature of especially Co-Fe Prussian blue

systems is the phenomenon of photoinduced magnetiza-tion or photoreversible enhancement of magnetization

[19-21] which has been observed in eg Rb18CoIII33Co

II07

[FeII(CN)6]33 middot 13H2O [2223] Na034Co133[Fe(CN)6] middot45H2O [19] or K04Co14[Fe(CN)6] middot 5H2O [20] Thesecompounds are efficient 3D-ferrimagnets at lowtemperatures (Tc lt 30 K) due to the presence of majorityof FeIIndashCNndashCoIII diamagnetic pairs which undergo uponirradiation photoinduced electron transfer resulting inparamagnetic FeIIIndashCNndashCoII species Such transform-ation is accompanied by elongation of the CondashN bondlengths (015ndash020 Aring) which is possible only in the caseof flexible inorganic network provided by the existenceof hexacyanidoferrate vacancies occupied by watermoleculesTransition metal hexacyanido complexes have been

also successfully utilized as building blocks for con-structing oligo- and polynuclear assemblies derived fromthe Prussian blue and a large number of such organicndashinorganic hybrid materials containing various organicligands mainly N-donor linear or macrocyclic ligandshave been extensively studied [24-28] These compoundswere also found to behave as molecular magnets [29]with potential applications as molecular devices ormemory devices Some of them also revealed very spe-cific optical properties including ion pair charge-transfer(IPCT) [30] transitions corresponding to the transfer ofelectrons from the complex anions to the complex cationsin the visible and near-ultraviolet spectral regions Thisphenomenon was confirmed for ionic pair compoundsinvolving both [Co(en)3]

3+ and [M(CN)x]4ndash (for x = 6

M = Fe Ru Os for x = 8 M =Mo W) complex ions [31]An irradiation of solutions containing these species intothe IPCT absorption band (λirr = 405 or 510 nm) leads to astructure re-arrangement and the formation of bi- ortrinuclear species For the ionic pairs [M(NH3)5L]

3+ and[Fe(CN)6]

3ndash (M = Ru Os L =NH3 or H2O) an inverse dir-ection of the electron transfer of the IPCT transition(from the cation to the anion) was found [32]Only eleven X-ray structures of discrete dinuclear

Co-Fecyanido-bridged complexes have been reported upto now whereas about ninety hits corresponding to poly-or oligomeric Co-Fe cyanido-bridged complexes have beendeposited within the Cambridge Structural Database upto now [33] Most of the dinuclear complexes have thegeneral formula of [LnCo

IIIndashNCndashFeII(CN)5]ndash where

Ln stands for a macrocyclic ligand and they have beensystematically studied by Bernhardt et al [34-36] Up todate similar number of ionic pair Co(III)-Fe(III)complexes have been structurally characterized Theyalways contain hexacyanidoferrate(III) anion and Co(III)complexed by ammonia [37] en [38-41] bipy [42-45] terpy[46] or other suitable ligands [47] Despite Co(III)-Fe(III)hexacyanidoferrates represent very important groupof compounds bearing a broad spectrum of importantphysico-chemical properties surprisingly only a little


attention has been paid to the monitoring of the thermalbehavior of these compounds [4849] Especially the factthat they can serve as suitable precursors for thermallyinduced solid-state synthesis of magnetic nanoparticles[5051] is almost unexploredThe dehydration process of the monohydrate [Co(en)3]

[Fe(CN)6]∙ H2O was previously described in details by ourworking group [40] and recently thermal decomposition of[Co(en)3][Fe(CN)6]∙ 2H2O in different atmospheres hasbeen published as well [52] In the present work we also re-port the thermal degradation of [Co(en)3][Fe(CN)6]∙2H2O(1a) which was obtained upon recrystallization from waterat 60degC But furthermore we concentrate on the progressof thermal decomposition of [Co(en)3][Fe(CN)6]∙2H2Ounder dynamic heating in air which includes the topotactic[53] dehydration process of the starting complex andgradual ligand liberationdecomposition resulting inthe formation of CoFe2O4-Co3O4 nanocomposite particlesas a final product of the thermal conversion Basedon the elemental and TGDSC analyses IR and 57FeMoumlssbauer spectra we suggest and discuss the uniquedecomposition mechanism accompanied by changesin the valence and spin states of both transitionmetal ions

Results and discussionSynthesis X-ray structure and spectral characterization of[Co(en)3][Fe(CN)6]middot 2H2O (1a)In contrast to our previous study which described atopotactic dehydration process of [Co(en)3][Fe(CN)6]∙H2O into [Co(en)3][Fe(CN)6] by means of single crystalX-ray analysis and Moumlssbauer spectroscopy [40] hereinwe strive to elucidate the mechanism of the thermaldecomposition of [Co(en)3][Fe(CN)6]∙ 2H2O based ona complete characterization of the decompositionintermediates The ionic pair [Co(en)3][Fe(CN)6]∙ 2H2Ocomplex was prepared by the straightforward reactionbetween [Co(en)3]

3+ and [Fe(CN)6]3ndash used as building

blocks in DMF [38] The efforts to prepare the titlecompound by an one-pot redox reaction in water usingCoCl2sdot 6H2O instead of [Co(en)3]Cl3∙ 3H2O were unsuc-cessful probably due to the incomplete coordination ofen and formation of Co(II)-involving PBA [23] Thesynthesis following the Bokrsquos published procedure led tothe formation of the dihydrated complex however twoproducts ie the dihydrated and monohydrated com-plexes can be obtained after the product recrys-tallization from hot water in dependence on the rate ofcooling of the solution Concretely the monohydrate isformed in the case of fast cooling of the solution heatedup to 90degC while the dihydrate is formed in the case ofslow cooling of the 60degC warm solutionAs first the molecular and crystal structures of 1a have

been determined by using single crystal X-ray analysis

(Figure 1 Table 1) The crystallographically independentpart of the molecule consists of the [Co(en)3]

3+

cation two halves of the [Fe(CN)6]3ndash moiety with the

iron(III) atoms lying on special positions (inversioncenters) and two crystal water molecules (Figure 1) Asthe structure posses an inversion center both Λδδδ (lel3)and Λλλλ (ob3) conformations of the [Co(en)3]

3+ cationsare present [54] The Co(III) atom is coordinated by sixnitrogen atoms from three chelating molecules of en in adistorted octahedral geometry The CondashN bond lengthsranges from 1955(2) to 1981(2) Aring (Table 2) and surpris-ingly these values are significantly shorter than thosedetermined for the same structure by Bok [1996(3)ndash2035(4) Aring] [38] For comparison very similar valueswere found for [Co(en)3]I3 middot H2O (1950(4)ndash1981(4) Aring)[55] and for [Co(en)3]Cl3 (1967(11) Aring) [56] while theyare much more distributed in [Co(en)3]3[FeCl6]Cl6middotH2O(1919(5)ndash2002(5) Aring) [57] The differences may becaused by the counter-ion that significantly influencesnon-bonding interactions within the crystal structureand thus a distortion in the vicinity of the central Co(III)atom can be found as a consequence of these inter-actionsIn the crystal structure the Fe(III) atoms are

coordinated by six carbon atoms originating from ter-minal cyanide groups While the Fe1C6 octahedron isalmost regular (the FendashC distances range from 1944(3)to 1951(3) Aring) the Fe1AC6 octahedron is slightlycompressed with the shorter axial Fe1AndashC2A distances(1932(3) Aring) as compared to the equatorial ones (1941(3) and 1946(3) Aring) (Table 2) Such type of deformationof the hexacyanidoferrate(III) anions was alreadyobserved eg in [(aed)2Cu2ClFe(CN)6]n middot 2H2O wherethe FendashC bond lengths range from 1931(4) to 1953(4)Aring [58] The remaining geometric parameters determinedfor [Fe(CN)6]

3ndash in 1a are comparable to those found forthe same complex anions in other compounds eg in[Ni(tren)]3[Fe(CN)6]2middot6H2O [59] or [Ni(en)2]3[Fe(CN)6]

2middot2H2O [60]The secondary structure of 1a is further stabilized by

the OndashH⋯O OndashH⋯N and NndashH⋯N hydrogen bondstogether with the CndashH⋯N and NndashH⋯C non-covalentcontacts connecting the complex ions and crystal watermolecules (Figure 2 Table 3)The information on the local electronic state of the

iron atom can be quantitatively obtained from 57FeMoumlssbauer spectra Concretely the isomer shift δwhich is related to the s-electron density at the nucleusand quadrupole splitting Δ related to the electric fieldgradient are crucial parameters sensitive to the oxida-tion and spin states of iron atom as well as its coordin-ation number Thus room temperature Moumlssbauerspectrum of 1a confirmed the presence of Fe(III) ions inlow-spin state because it consists a symmetrical doublet

Figure 1 Molecular structure of [Co(en)3][Fe(CN)6]sdot 2H2O (1a) The thermal ellipsoids are drawn at the 50 probability level


with isomer shift δ = minus017 mms and quadrupole split-ting ΔEQ = 085 mms (Figure 3) The values of theseparameters are typical for the hexacyanidoferrate(III)anion [61] In measured IR spectra typical sharp andstrong absorption bands at 2117 and 2107 cmndash1

corresponding to the υ(CequivN) stretching vibration wereidentified (Figure 4) They well document the presenceof terminal coordinated cyanide groups because the vi-bration frequency of free CNndash anion (about 2080 cmndash1)is blue shifted due to a coordination (removing electronsfrom weakly antibonding 5σ orbital during metal-carbonσ bond formation) like in K3[Fe(CN)6] which displaysone sharp absorption band at 2118 cmndash1 [4162] Incomparison with K3[Fe(CN)6] there is a splitting of theabsorption band that can be explained by loweringof the Oh site symmetry of the hexacyanidoferrate(III) anion Otherwise broad absorption bands due tothe OndashH (~3380 cmndash1) NndashH (~3234 cmndash1) or CndashH(~3095 cmndash1) stretching as well as deformationvibrations (NH2 1630ndash1578 cmndash1) are present togetherwith the pattern of fingerprint region corresponding tothe three coordinated molecules of en (the full IRspectrum is available in Additional file 1 Figure S1)The temperature dependence of the effective magnetic

moment (for details see Additional file 1 Figure S2)revealed weak antiferromagnetic interactions The effect-ive magnetic moment of 1a at room temperature was 223BM and it is gradually decreased to 184 BM as thetemperature was reduced to 2 K Its value was higher thanexpected for the spin-only value of 173 BM for S = 12but similar to the value of 225 BM obtained for K3

[Fe(CN)6] [63] Fitting of the reciprocal susceptibility(see Additional file 1 Figure S3) above 50 K byCurie-Weiss law gave g = 267 and Θ = minus19 K for S = 0 and

S = 12 for CoIII and FeIII respectively The higher valuesof g-factors have been previously observed for other low-spin FeIII complexes as well [64]

Thermal behavior of [Co(en)3][Fe(CN)6]∙ 2H2O (1a) ndash ageneral overviewThe TG and DSC curves of 1a are displayed in Figure 5TG curve of 1a reveals two separable steps of the ther-mal decomposition The first weight loss occurs in thetemperature range of 50ndash80degC and it is accompanied byendothermic effect with the minimum at 80degC as can beseen on DSC curve (Figure 5) Experimental weight loss(56) is in good agreement with the calculated one(55) corresponding to the release of 15 crystal watermolecules from the formula unit of 1a and thus yieldingthe complex [Co(en)3][Fe(CN)6]∙ 12H2O (1b) asconfirmed by chemical and single crystal X-ray analysesThe hemihydrate 1b is thermally stable within thetemperature interval of 72ndash187degC The second step ofthe thermal decay is observed in the temperature rangeof 187ndash420degC and involves continual and complete sam-ple decomposition Based on the course of DSC curve itcan be stated that at least three processes take place (i)a weak exothermic process with the maximum at 208degC(ii) an endothermic process with the minimum at 214degCand (iii) a strong exothermic effect with the maximumat 354degC The sample weight loss corresponding to thesecond step was found to be 617 It can be assigned toelimination of the remaining water content allmolecules of ethylenediamine as well as all CNndash ligandsandor oxidation of the transition metal ions yielding aspinel-type phase with the general chemical compositionof Co15Fe15O4 (calculated weight loss 621) Incomparison with the thermal decomposition of 1a

Table 1 Crystal data and structure refinements for 1aand 1b

1a 1b

Formula C12H28CoFeN12O2 C24H50Co2Fe2N24O

Formula weight 48724 92044

Crystal system monoclinic monoclinic

Space group P21n P21c

Unit cell dimension

a [Aring] 82822(2) 150448(3)

b [Aring] 165364(3) 84631(2)

c [Aring] 145365(3) 149812(3)

β [deg] 91988(2) 90160(2)

Z 4 2

V[Aring3] 198969(7) 190748(7)

Dcalc [gcmndash3] 1627 1603

T [K] 100 100

μ [mmndash1] 1599 1658

Index ranges minus9le h le 9ndash16 le kle 19

minus17 le h le 17ndash8le k le 10

minus17 le l le 17 minus17 le lle 17

θ-range for data collection 275ndash2510 271ndash250

Reflection collected 13225 9451

Independent reflections 3533 [Rint = 00286] 3348 [Rint = 00164]

Datarestrainsparameters 3533 4 250 3348 2 247

Goodness-of-fit on F2 1169 1246

Final R indices R1 = 00265wR2 = 00807

R1 = 00263wR2 = 00796

R indices (all data) R1 = 00354wR2 = 00976

R1 = 00333wR2 = 00949

Largest diff peak and hole 0444 and minus0424 0465 and minus0627

Table 2 Selected bond lengths (Aring) and angles (deg) for 1aand 1b

1a 1b

Co1ndashN7 1955(2) Co1ndashN4 1964(2)






Fe1AndashC1A 1941(3) Fe1AndashC1A 1947(3)



Fe1ndashC1 1951(3) Fe1ndashC1 1941(3)



N7ndashCondashN8 8559(9) N4ndashCondashN5 8540(9)




recently published in Ref [52] the decomposition of 1aoccurs at lower temperature in our case which can beassociated to different experimental conditions andmoreover CoFe2O4 only was determined as the finaldecomposition product [56] Unstable intermediates[FeII(en)2(μ-NC)CoIII(CN)5] [Fe

III(H2NCH2CH3)2(μ-NC)

2CoII(CN)5] and FeIII[CoII(CN)5] were identified during

this complicated decomposition The detailed descrip-tion of the above-mentioned processes with identifica-tion of the intermediates by XRD method Moumlssbauerand IR spectroscopy and transmission electron micros-copy (TEM) will be discussed below mainly from thechemical point of view (vide infra)

Chemical structural and spectral characterization of[Co(en)3][Fe(CN)6]∙12H2O (1b) formed in the firstdecomposition stepThe complex [Co(en)3][Fe(CN)6]∙ 12H2O (1b) as it wasalready mentioned can be obtained as a stable

intermediate by both dynamic or static heating of thedihydrate 1a up to 130degC (Table 4) The empirical for-mula of 1b was deduced from the elemental analysisresults and well corresponds to the weight loss on theTG curve (Figure 5) The parameters of Moumlssbauerspectrum of 1b (δ = minus015 mms and ΔEQ = 098 mms)exhibit small changes as compared to the correspondingvalues of 1a (δ = minus017 mms and ΔEQ = 085 mms)Generally the found hyperfine parameters refer to thepresence of Fe(III) cations in the low-spin state in bothcomplexes Small increase in the quadrupole splittingvalue is evidently related to a small decrease in the sym-metry of the iron atom surroundings as a consequenceof the topotactic dehydration process Similar findingsconnecting with the variations in Moumlssbauer parametersdepending on a number of crystal water moleculespresented in the structure were previously observed fora series of M3[Fe(CN)6]2 middot nH2O complexes (M =Ni MnCo Cu Cd n can rise up to 14) [61] There is only verysmall difference in measured IR spectra between 1a and1b because all above described absorption bands for 1aare also present in the spectrum of 1b (Figure 4)The single crystal character is preserved during the

dehydration process of 1a to 1b what is generally a veryrare phenomenon among coordination compoundsalthough it is quite common for simple salts egK035CoO2middot 04H2O [65] manganese(II) formate [66] orFePO4 [67] To our knowledge the single crystal dehy-dration process was reported only for a series ofpolymeric compounds [M(H2O)2(C4O4)(bipy2)]∙ H2On(M = Co Ni Fe) [68] and [Ni(en)3]3[Fe(CN)6]2 middot 2H2O[60] up to date

Figure 2 Part of the crystal structure of [Co(en)3][Fe(CN)6]sdot 2H2O (1a) showing selected non-covalent contacts (dashed lines) The CH2

groups of the ethylenediamine ligands are omitted for clarity The thermal ellipsoids are drawn at the 50 probability level


The molecular structure of the hemihydrate 1b(Figure 1 Tables 1 and 2) is analogous to that of the ori-ginal dihydrate 1a since it is composed of the samecomplex cations and anions Main but not significantstructural variances between 1a and 1b are caused bythe presence of different number of crystal watermolecules Thus the dehydration process is accompan-ied by small shifts only in the positions of the respective[Co(en)3]

3+ and [Fe(CN)6]3ndash ions as can be deduced

from the mean values of the Co⋯Fe distances to the sixnearest neighbors which were found to be 632(4) and622(4) Aring in the crystal structures of 1a and 1b respect-ively Both 1a and 1b crystallize in the monoclinic sys-tem in related space groups (ie P21n for the dihydrateand P21c for the hemihydrate) but with the differentunit cell orientations towards the presented moleculesThe relationship between two unit cell settings can beexpressed by the equation (aH bH cH) = (010100 00ndash1)(aD bD cD) where aD bD cD and aH bH cH stand forcell parameters of the hemihydrate (H) and dihydrate(D) respectively It should be noted that the monoclinicangles in both unit cells [βD = 91982(4)deg and βH = 9015(1)deg] display only minor deviation from the right angleAs expected the unit cell dimensions of the hemihydrate1b are somewhat shorter in lengths as compared to thedihydrate 1a Therefore the dehydration process fromthe dihydrate (1a) to the hemihydrate (1b) can beconsidered as topotactic because of minimal geometricchanges (less than 4) and minimal atomic and molecu-lar movements (change of each intra-intermoleculardistances lt 42 Aring) [53]

Despite considerable similarity between both struc-tures also some differences can be found The partialdehydration caused conformational change within the[Co(en)3]

3+ cations While the Λδδδ (and Δλλλ) con-formation was observed in 1a the Λλδδ (and Δδλλ) con-formation was found in 1b (Figure 6) It can be assumedthat these conformational variations are induced bychanges in the hydrogen bonding interactions (seebelow) as was previously suggested in conformation ana-lysis of [M(en)3]

3+ (M = CoIII CrIII) [54] Moreover to-gether with the conformational changes within the [Co(en)3]

3+ cations the shortening in the CondashN bondlengths in the hemihydrate 1b (1956(2)ndash1968(2) Aring)were found as compared to those in 1a (1955(2)ndash1981(2) Aring) However all these values are comparable to thosedetermined for the same cation in similar systems (197(7) Aring) [33]Two crystallographically independent centrosymmetric

[Fe(CN)6]3ndash moieties (both iron(III) atoms occupy spe-

cial positions ndash the inversion centers) are present in thestructure of 1b similarly as in the structure of 1aBoth Fe1C6 and Fe1AC6 octahedra in 1b are slightlydeformed The octahedron around the Fe1A atom iscompressed (Table 2) with the axial Fe1AndashC2Adistances (1927(3) Aring) being shorter than the equatorialones (1947(3) and 1943(3) Aring) Similar compression wasfound in the vicinity of the Fe1 atom with the axialFe1ndashC3 distance (1928(3) Aring) and longer equatorialdistances (1946(3) and 1941(3) Aring) All these FendashC bondlengths as well as other interatomic parameters are fromthe range of typical values for [Fe(CN)6]

3ndash anions

Table 3 Selected hydrogen bonds for 1a and 1b (Aring deg)

DndashH A d(DndashH) d(H A) ang DHA d(D A)

1a

O1ndashH1V O2 092 199 1768 2905(2)

O1ndashH1W N3 100 208 1638 3050(3)

O2ndashH2V N3Ai 101 183 1616 2807(3)

O2ndashH2W N2i 077 212 1639 2862(3)

N7ndashH7D O2 092 200 1592 2882(3)

N7ndashH7C N1 092 208 1591 2960(3)

N8ndashH8C N1Aiii 092 235 1368 3083(3)

N9ndashH9D N2Aiii 092 255 1303 3227(3)

N9ndashH9D N2i 092 244 1406 3205(3)

N10ndashH10C N3ii 092 235 1532 3203(3)

N10ndashH10D N2A 092 242 1455 3226(3)

N11ndashH11C N3ii 092 215 1580 3019(3)

N11ndashH11D N2i 092 235 1453 3153(3)

N12ndashH12C N1 092 239 1510 3227(3)

N12ndashH12D N2A 092 208 1653 2976(3)

1b

O1ndashH1W N3i 120 167 1393 2695(7)

N4ndashH4C N2Aiii 092 212 1594 2997(3)

N5ndashH5C N1Aiv 092 220 1514 3039(3)

N5ndashH5D O1 092 193 1467 2742(7)

N6ndashH6C N1 092 232 1431 3108(3)

N6ndashH6D N1A 092 243 1371 3168(3)

N7ndashH7C N2Aiii 092 219 1459 2996(3)

N7ndashH7D N3i 092 220 1569 3069(4)

N8ndashH8D N3 092 219 1480 3015(4)

N9ndashH9C N1v 092 231 1437 3102(3)

N9ndashH9D N2ii 092 206 1488 2887(3)

Symmetry codes (1a) i x + 12 ndashy + 12 zndash12 ii xndash12 ndashy + 12 zndash12 iiix + 12 y zSymmetry codes (1b) i x y + 1 z ii x ndashy + 12 z + 1 iii ndashx + 1 ndashy + 1 ndashziv ndashx + 1 y + 12 ndashz + 12 v ndashx + 2 ndashy + 1 ndashz


Generally it can be anticipated that the topotactic de-hydration may influence significantly an extent of hydro-gen bonds and other non-covalent contacts presentedwithin the crystal structures Thus as a consequence ofthis general statement the number of the above-mentioned non-bonding interactions is slightly lowerand moreover they are moderately shorter than those inthe crystal structure of 1a While in the crystal structureof the dihydrate 1a the water molecules are connectedwith [Fe(CN)6]

3ndash anions via hydrogen bonds of the typeOndashH⋯N and OndashH⋯O the OndashH⋯O hydrogen bondis absent in the crystal structure of 1b (Table 3Figure 7)The magnetic properties of the hemihydrate 1b (see

Additional file 1 Figure S2 and S3) are similar compared

to those for the dihydrate 1a Fitting of the temperaturedependence of reciprocal susceptibility above 50 K byCurie-Weiss law gave g = 277 and Θ = minus18 K indicatingslightly weaker antiferromagnetic interaction in compari-son with 1a The effective magnetic moment of 1b atroom temperature is similar to the value for 1a but asmall difference becomes visible when the temperaturedeclines below 50 K (Additional file 1 Figure S2) wherethe values of μeff for 1b are slightly higher than those for1a and thus indicating weaker antiferromagneticinteractions Such observation is in accordance with thetopotactic dehydration process which reduces the num-ber of intra-molecular interactions as was observed inthe crystal structure of 1b The completed CIF files for1a and 1b can be found as Additional files 2 and 3respectively

Chemical structural and spectral characterization of theintermediates formed during the second and thirddecomposition stepsTo explain the unexpected exothermic effects in DSCcurves accompanying the evolution of molecules of en athigher temperatures and generally to understand thestructure and chemical composition of intermediatesformed during the appropriate stage of the thermal treat-ment the complex 1a was heated dynamically inconditions of the DSC experiment up to the selectedtemperatures and the samples were analyzed consequentlyby Moumlssbauer and IR spectroscopy and elemental analysisThe results obtained from these measurements togetherwith the proposed composition of conversion inter-mediates are summarized in Table 4 The suggested de-composition model for 1a is depicted in Scheme 1When 1a was heated up to 240degC (sample 2) the color

of sample turned from orange to green It wasdemonstrated by DSC that this solid underwent an exo-effect with the maximum at 208degC followed by an endo-effect with the minimum at 214degC The Moumlssbauerspectrum of 2 consists of four doublets which corres-pond to iron-containing species in two different oxida-tion states (see Figure 3 and Table 4) Three doubletswith δ values ranging from 102 to 131 mms corres-pond clearly to the high spin Fe(II) atoms [6970] Thehigh values of quadrupole splitting parameters (195ndash253 mms) manifest a very low symmetry of the Fe(II)environment as expected for the coordination number 5[69] The presence of three broadened Fe(II) doubletsvarying in the values of ΔEQ is probably related to thevarious degrees of the deformation of the iron(II) envir-onment The most populated doublet (δ = 022 mmsΔEQ = 060 mms) can be ascribed to a high spin Fe(III)environment in tetrahedral coordination [70] The in-crease of the isomer shift in comparison with 1a or 1bcan be attributed to the iron spin transition from low to

Figure 3 A representative Moumlssbauer spectrum of [Co(en)3][Fe(CN)6]sdot 2H2O (1a) at 25degC and spectra of the convertedintermediates formed by heating of 1a up to 240 300and 350degC

Figure 4 Part of the room temperature IR spectrum of [Co(en)3][Fe(CN)6]sdot 2H2O (1a 25degC) and its comparison with the IRspectra of the corresponding decomposition intermediates atthe temperatures of 150 230 265 and 450degC


high spin as well as to the different coordination modeof cyanide ion to Fe(III) (FeIIIndashCN in 1ab FeIIIndashNC in2) [50] The results of Moumlssbauer spectroscopy give anevidence for the surprising change of the spin state of alliron atoms between 130 and 240degC as all the spectralcomponents correspond to the high-spin states More-over the presence of divalent iron indicates a centralatom reduction which accompanies oxidation of CNndash to(CN)2 The formed cyanogen can react with twomolecules of en which are also liberated during thisthermolytic step and one bicyclic molecule of bis(Δ2-2-imidazolinyl) [71] could be formed as a potential prod-uct of the decomposition (see Scheme 1) All thementioned experimental results can be explained by theformation of the bridging [FeII(en)2(μ-NC)CoIII(CN)4]complex from the hemihydrate 1b (see step II inScheme 1) what is in accordance with the preference ofHS Fe(II) to be coordinated in weaker ligand fieldprovided by N-donor atoms rather than C-donor atomsIt seems that the complete dehydration induces a drastic

rearrangement of the environments of both centralatoms related to the evolution of half molecule of cyano-gen and one molecule of en from the formula unit of 1bwhich is probably reflected on the DSC curve by thementioned exo-effect at 208degC Nevetheless similarprocess of deamination has been described previously on

Figure 5 TG (dotted) and DSC (full) curves of complex [Co(en)3][Fe(CN)6]sdot 2H2O (1a) Data were recorded in the temperature interval of 20ndash500 and 20ndash400degC respectively and with the heating rate of 5degCmin


other systems containing [Co(en)3]3+ and it was always

accompanied by a strong endo-effect above 200degC onthe DSC curve [72] Thus the following endo-effect at214degC on the DSC curve could be ascribed to the liber-ation of en as wellThe simultaneous presence of the high spin Fe(II)

and Fe(III) species in sample 2 can be related to thepartial transformation of [FeII(en)2(μ-NC)CoIII(CN)4] to

Table 4 Room temperature Moumlssbauer parameters and the cothe samples prepared by its dynamic heating up to 130ndash600deg

Sample number T [degC] phase δ [mms] ΔEQ [mms] Hhyp [T]

1a 25 LS Fe(III) minus017 085 ndash

1b 130 LS Fe(III) minus015 098 ndash

2 240 HS Fe(II) 117 225 ndash

HS Fe(II) 131 253 ndash


HS Fe(III) 022 060 ndash

3 300 HS Fe(II) 114 249 ndash


4 350 HS Fe(III) 026 043 ndash




HS Fe(III) 029 minus001 426




(LS) low-spin state (HS) high-spin state (SP) superparamagnetic particles (RA) relat

[FeIII(NH2CH2CH3)2(μ-NC)2CoII(CN)3] (see step III in

Scheme 1) This charge transfer process has been previ-ously observed and confirmed in many FeIIndashCNndashCoIII

species (light-induced magnetization changes) [19-23] andhere it is more pronounced at higher temperature asclearly seen from the comparison of the Fe(II)ΣFe ratio of034 found in sample 2 heated up to 240degC with thatobserved in sample 3 heated up to 300degC (018 see Table 4

rresponding elemental analyses of complex 1a as well asC

RA [] Elemental analyses [] Assignment

N C H

100 344 298 55 [CoIII(en)3][FeIII(CN)6]sdot 2H2O

100 360 312 54 [CoIII(en)3][FeIII(CN)6]sdot frac12H2O

130 313 332 39 [FeII(en)2(μ-NC) CoIII(CN)4]

114

100

656 [FeIII(NH2CH2CH3)2(μ-NC)2 CoII(CN)3]



557 199 228 20 [FeIII(NH2CH2CH3)2(μ-NC)2 CoII(CN)3]

443 FeIII[CoII(CN)5]

100 0 0 0 CoFe2O4 (SP)

468 0 0 0 CoFe2O4 (SP)

532 CoFe2O4

34 0 0 0 CoFe2O4 (SP)

791 CoFe2O4

175 CoFe2O4

ive abundance

Figure 6 Molecular structure of [Co(en)3][Fe(CN)6]sdot 12H2O (1b) The thermal ellipsoids are drawn at the 50 probability level

Traacutevniacuteček et al Chemistry Central Journal 2013 728 0 of 18httpjournalchemistrycentralcomcontent7128

and Figure 3) In this third decomposition step we assumethe participation of atmospheric oxygen and gradual evo-lution of NOX This assumption is in an accordance withthe NC ratio decrease between 240 (094) and 300degC(084 see Table 4) The step III is manifested in DSC curvethrough a long endo-effect with the minimum at 214degC or

Figure 7 Part of the crystal structure of [Co(en)3][Fe(CN)6]sdot 12H2O (1bHydrogen atoms of the CH2 groups of the en ligands are omitted for clarit

rather long exo-effect in the temperature range of 220ndash300degC without specified maximum (see Figure 5) It isworth to mention that both samples 2 and 3 revealed adrastic lowering of conductivity compared to hemihydrate1b which is in line with the presence of bridging ligandsbetween Co and Fe central atoms in the dinuclear species

) showing selected non-covalent contacts (dashed lines)y The thermal ellipsoids are drawn at the 50 probability level

[CoIII(en)3][FeIII(CN)6]times2H2O


[FeII(en)2(micro -NC)CoIII(CN)4]

[FeIII(NH2CH2CH3)2(micro -NC)2CoII(CN)3]

FeIII[CoII(CN)5]

12 CoFe2O4 + 16 Co3O4

-32 H2O

-12 H2O

-(en + CN)

en + 12 (CN)2

NH

N HN

N Exo (max 208degC)

Endo (min 214degC)

Exo (max 354degC)

Exo (max 354degC)

Endo (min 80degC)

+ O2 -(NH2) NOx + H2O

-2 H2NCH2CH3

+ O2 -5 (CN)

step I

step II

step III

step IV

step V

Fe

N

N

N

N

Co

CN

CN

CN

CN

Fe CoH2N

H2N

CN

CN

CN

CO2NOxH2O

+ O2

CO2 + N2

(1a)

(1b)

NC

NC

NC

Scheme 1 Suggested scheme of thermal decomposition of [CoIII(en)3][FeIII(CN)6]sdot 2H2O (1a) during dynamic heating in air atmosphere

(Endo stands for endo-effects while Exo for exo-effects)


IR spectra recorded for the intermediates in sample 2and 3 (230 and 265degC Figure 4) confirmed proposed ther-mal decomposition mechanism The υ(CequivN) stretching vi-bration is significantly governed by the electronegativityoxidation state and coordination number of the metal cen-tral atom directly bonded to the cyanide group Thus theformation of cyanido-bridged species is accompanied by asignificant broadening of the υ(CequivN) bands observed inIR spectra Furthermore the shift of the peak at 2113 cmndash1

toward higher wave numbers with increasing temperature(2113rarr 2127rarr 2132 cmndash1 for 150rarr 230rarr 265degC)documents the oxidation state changes and could beassigned to υ(FeIIndashCNndashCoIII) The intensity of this vibra-tion band decreases with higher temperature whichindicates absence of such type of coordination above265degC On the other hand the shift of the peak at2104 cmndash1 toward lower wave numbers with increasingtemperature (2104rarr 2062rarr 2066 cmndash1 for 150rarr 230rarr265degC) corresponds to υ(CoIIndashCNndashFeIII) [50] This obser-vation confirms the proposed decomposition mechanism

concerning increasing amount of [FeIII(NH2CH2CH3)

2(μ-NC)2CoII(CN)3] at higher temperature (see step III in

Scheme 1 and Table 4) and it indicates that CoIIndashCNndashFeIII

is the most probable coordination bridge in [FeIII

(NH2CH2CH3)2(μ-NC)2CoII(CN)3] Although non-linear

coordination mode of bridging cyanide in dipolynuclearcomplexes is known the suggested structure of [FeIII

(NH2CH2CH3)2(μ-NC)2CoII(CN)3] requires two cyanide

bridges of that type Such coordination tension could bereduced if the formation of a structure with the cyclictetranuclear Fe2Co2(CN)4 core is considered Moreovercompounds with similar core-structure have beendescribed recently [73] Another possibility is the forma-tion of a polymeric structure with μ3-CN coordinationmode found in the case of several Cu(I)ndashZn(II) complexes

Chemical structural and spectral characterizations of theintermediates formed in the fourth decomposition stepAlthough the samples 2 and 3 differ in quantitativecharacteristics mainly in the C and N contents and in

Figure 8 Room temperature Moumlssbauer spectra of thedecomposition products prepared by dynamic heating of 1a upto 450degC (sample 6) and 600degC (sample 7)


the percentage of Fe(II) and Fe(III) species their phasecomposition is similar from the qualitative viewpoint asevident from hyperfine parameters of Moumlssbauerspectra The next principal chemical change in thechemical composition of the samples takes place afterheating up to 350degC (sample 4) This fourth reactionstep is reflected on the DSC curve at 335degC by a shoul-der of exo-effect at 354degC and documented also by aconsiderable diminution of both C and N contents (seeTable 4) In Moumlssbauer spectrum of the sample 4 (seeFigure 3) heated up to 350degC there are no indications ofthe divalent iron species in contrast to the roomtemperature spectra of samples 2 and 3 On the otherhand a new high-spin Fe(III) phase with δ = 046 mmsand quadrupole splitting ΔEQ = 122 mms appears inthe spectrum along with the residual doublet ascribed to[FeIII(NH2CH2CH3)2(μ-NC)2Co

II(CN)3] as its hyperfineparameters are almost unchanged compared to thespectrum of sample 3 The hyperfine parameters of theformer species are in a very good accordance with thoseobserved for iron complexes with pentacoordinated highspin Fe(III) environments [74] Thus this new phasewith the low symmetry of iron environment which ismanifested by a high value of quadrupole splitting canbe ascribed to FeIII[CoII(CN)5] As for the expectedchemical nature of the gases evolved during the fourthdecomposition step leading from [FeIII(NH2CH2CH3)2(μ-NC)2Co

II(CN)3] to FeIII[CoII(CN)5] (see step IV inScheme 1) their experimental identification usingevolved gas analysis (EGA) may be ambiguous due tothe negative role of atmospheric nitrogen and oxygenNevertheless previous decomposition studies of othercomplexes with en eg [Ni(en)3](ox) [75] using EGAshowed that en is decomposed to a mixture of H2COCO2 N2 and CH2 = CH2 in an inert atmosphereThus the decomposition of ethylamine in air may in-volve similar or more oxygen containing species such asH2O CO CO2 N2 or NOx

Characterization of the final decomposition product ndash thefifth decomposition stepIn accordance with TG data decomposition process iscompleted in dynamic conditions at 420degC As men-tioned above the overall weight loss corresponds wellwith the final formation of the M3O4 (M = Fe Co) phase(s) which is in accordance with the absence of υ(C equivN)stretching vibration bands in IR spectrum (Figure 4450degC) Taking into account the starting molar ratio ofFeCo = 11 various combinations of several oxides(CoFe2O4 Fe3O4 Fe2O3 polymorphs Co3O4 FeCo2O4)come on force to express the phase composition of thefinal product The isomer shift values in roomtemperature Moumlssbauer spectra of the final decompos-ition products formed after dynamic heating of 1a up to

450 and 600degC (samples 5 6 and 7 see Table 4 andFigure 8) unambiguously exclude the presence of diva-lent iron (Fe3O4 FeCo2O4) in the iron oxide phase [76]The spectra of the samples 5 and 6 heated up to 400and 450degC display a broadened doublet as a prevailingcomponent which can be ascribed to superparamagneticnanoparticles Superparamagnetic character of the spec-tra disallows the identification of iron(III) oxide phase(CoFe2O4 vs γ-Fe2O3 vs α-Fe2O3) in all samples In thespectrum of sample 6 heated to 450degC the prevailingdublet is accompanied by a completely magnetically splitsextet which becomes the major signal observed in thespectrum of sample 7 prepared by heating of 1a up to600degC (see Figure 8) This reduction of the ratio betweenthe intensity of the dublet (superparamagnetic particles)and sextet manifests the formation of larger particles(~50 nm) due to the proceeding crystallization processThe room temperature spectrum of sample 7 can be fit-ted by two six-line hyperfine patterns with the nearly thesame isomer shift (029 and 037 mms) and hyperfinemagnetic fields of 486 and 514 Generally the isomershift parameters are closed to those reported forCoFe2O4 [77] and γ-Fe2O3 (027 mms) [78] orhematite α-Fe2O3 (038 mms) [78] Two sextetsdiffering in isomer shift and hyperfine magnetic fieldcan be ascribed to Fe(III) ions located at the tetrahe-dral (Td) δ = 037 mms Hhyp = 514 T and octahedral


(Oh) δ = 029 mms Hhyp = 486 T sites of the partially in-verse spinel structure of CoFe2O4 In comparison withbulk CoFe2O4 (512 T for Td-site 550 T for Oh-site) thevalues of Hhyp of prepared CoFe2O4 nanoparticles (426 Tfor sample 6 486 and 514 T for sample 7) are smallerdue to their lower crystallinity [79]In Figure 9 the XRD spectrum of sample 7 is shown

which consists of two sets of peaks corresponding to twospinel phases The presence of γ-Fe2O3 or α-Fe2O3 isclearly excluded because the first set of peaks correspondsto CoFe2O4 phase [77] (marked with asterisks) and the sec-ond pattern belongs to Co3O4 (labeled with short verticallines) According to the XRD data the molar ratio betweenthese two phases was found to be 244 1 (CoFe2O4 Co3O4) what is in accordance with the proposed stoichi-ometry of both phasesTo confirm the inverse spinel phase formed during the

heating of 1a up to 600degC and reveal the magnetic struc-ture the in-field Moumlssbauer spectrum of sample 7 wasrecorded (Figure 10 Table 5) It consists of two overlap-ping six-line hyperfine patterns corresponding to Fe(III)in Td- and Oh-sites of spinel lattice (partial separation ofboth patterns) The data were successfully fitted withtwo sextets having the δ = 038 mms ΔEQ = minus002 mmsand Hhyp = 526 T corresponding to Fe(III) in Td-site andδ = 054 mms ΔEQ = minus008 mms and Hhyp = 490 T forFe(III) in Oh-sites respectively The degree of conversionfor inverse spinel x which identifies its formula Fe(III)xCo(II)1ndashx[Co(II)xFe(III)2ndashx]O4 (brackets indicate ions atOh-site) can be calculated on the basis of the relativecontribution of individual Td- and Oh-site sextets Thevalue of x was obtained from the equation x = 2 k(1 + k)where k is the ratio between Fe(III) ions in the tetrahedral

Figure 9 XRD pattern of the sample prepared by heating of 1a up to

and octahedral sublattices calculated from the ratio be-tween the areas of individual sextets corresponding to Td-and Oh-sites The obtained value of x = 09 indicates theformation of partiallyalmost fully inverse spinel structureFe(III)09Co(II)01[Co(II)09Fe(III)11]O4 The determinationof the degree of inversion at low temperature in externalmagnetic field is more accurate in comparison withroom temperature spectra (Figure 8) because the appliedmagnetic field better separates the Td- and Oh-sitecontributions (sextets) and the low temperature reducesthe vibrations of the lattice andor the Moumlssbauer nucleus(significantly influence the ration between the Td- andOh-signals)The intensities of 2nd and 5th lines are lower than

expected for a thin sample with randomly oriented mag-netic moments in the absence of magnetic field (ideally321123) which is characteristic for the materials inferromagnetic andor ferrimagnetic state and whichcorresponds to the partial alignment of the iron mag-netic moments in the direction of the external magneticfield If the iron magnetic moment were completelyaligned the 2nd and 5th lines would be completelyvanished Thus the presence of the 2nd and 5th lines inthe spectrum points out to the canting of Fe(III) spin inCoFe2O4 particles with respect to the direction of theexternal magnetic field Based on the comparison of theareas corresponding to 25 and 16 lines the averagespin-canting angle θ was evaluated on the basis of theformula θ = arccos[(4ndashs)(4 + s)]12 [80] where s = A25A34 and was calculated to be 303deg (from both Td- andOh-sites) The thickness of the spin-canted surface layerof the sample was not deduced because the shape ofprepared particles was not considered as spherical

600degC () CoFe2O4 (|) Co3O4

Figure 10 In-field (5 K 5 T) Moumlssbauer spectrum of theCoFe2O4 spinel phase formed by heating of 1a up to 600degCCrosses represent the experimental data and the upper and middlefull lines represent the subspectra obtained from the fittingprocedure for iron atoms in T- and O-sites respectively and thelower full line represents their sum External field was appliedparallel to the γ ray propagation


The morphology of the product formed by heating of1a up to 600degC (sample 7) is clearly visible on TEMpictures (Figure 11) which confirm the nanocompositestructure of the CoFe2O4ndashCo3O4 particles But thesenanoparticles taken directly after the thermal decom-position form agglomerates and are not well-dispersedand thus their median size based on TEM analysis wasnot calculated

ConclusionsThe thermal decomposition of [Co(en)3][Fe(CN)6]∙2H2O (1a) in air atmosphere was monitored by TGDSCtechniques Seven samples were prepared by annealing1a at selected temperatures which were completelycharacterized by elemental analyses IR and 57Fe

Table 5 Hyperfine parameters of in-field Moumlssbauer spectrum

Position of the Fe+3 ions δ plusmn 001(mms)

ΔEQ plusmn 001(mms)

Beff plusmn 03 (T) Γ plusmn(mm

T-site 038 minus002 526 054

O-site 054 minus008 490 063

Where δ is center shift ΔEQ is quadrupole splitting Beff is effective magnetic field Γand A34 are the intensities of the secondfifth and thirdfourth lines respectively

Moumlssbauer spectroscopies with the aim to elucidate thedecomposition mechanism It has been found that thetopotactic dehydration of 1a led to the formation of thehemihydrate [Co(en)3][Fe(CN)6]∙ 12H2O (1b) whichwas consequently decomposed in next four stepsgoing through the [FeII(en)2(μ-NC)CoIII(CN)4] [FeIII

(NH2CH2CH3)2(μ-NC)2CoII(CN)3] and FeIII[CoII(CN)5]

intermediates leading to CoFe2O4-Co3O4 nanocom-posite particles at as the final product (confirmed byTEM) It has been shown that a relatively small changeregarding the heating gradient (5degCmin in this workversus 10degCmin in Ref 52) may substantially influencethe composition and particle size of the final productMoreover from a general point of view the obtainedresults also revealed that the thermal decomposition ofsuch a simple salt as [Co(en)3][Fe(CN)6]∙ 2H2O involvesa relatively complicated mechanism driven mainly by thereaction conditions (such as the heating gradient and airatmosphere) and is composed by several overlappingsteps and resulting in the formation of interestingnanoparticles with a nanocomposite structure of twomagnetically different phases It may be anticipated thatthe modulation of their properties would be possible bythe exact control of the temperature (gradient orprolonged heating or amine-ligand substitution) and fur-ther investigation of magnetic properties of such systemwould be very interesting and helpful

ExperimentalMaterials and reagentsK3[Fe(CN)6] (Merck) and NNrsquo-dimethylformamide(Lachema Brno) were purchased from commercialsources and used as received [Co(en)3]Cl3∙ 3H2O wasprepared by a slightly modified procedure described inthe literature [81]

Synthesis[Co(en)3][Fe(CN)6]∙ 2H2O (1a)039 g (1 mmol) of [Co(en)3]Cl3∙ 3H2O and 032 g (1 -

mmol) K3[Fe(CN)6] were added into 20 ml of NNrsquo-dimethylformamide (DMF) with stirring and refluxed for1 h The yellow-orange precipitate formed in the reac-tion mixture and the color of the solvent changed intolight-green The solid was filtered off and consequentlydissolved in 30 ml of warm water (60degC) The solutionwas left to stand at room temperature Yellow-orange

of sample 7 at 5 K and in external field 5 T

001s)

RA plusmn 3 A25A34 Cantingangle (deg)

Average canting angle ofboth sites (deg)

45 0579 302 303

55 0589 304

is line width and RA is the relative area of individual sextets Furthermore A25

Figure 11 TEM micrograph of the sample prepared by heating of 1a up to 600degC demonstrating the presence of CoFe2O4-Co3O4 in theform of nanocomposite particles


crystals were obtained by slow evaporation of the solventafter several hours They were filtered off washed withsmall amount of cold water and dried on air (yield 55)Anal calc for C12H28N12CoFeO2 C 298 H 58 N347 Found C 302 H 55 N 344 IR 3381 bm3279 s 3232 bs 3095 bs 2117 vs 2107 vs 1630 m1609 m 1578 m 1464 m 1399w 1334 m 1289 w1156 m 1143 m 1051 m 763 w 580 m

Physical measurementsElemental analyses (C H N) were performed on aFlash EA 1112 Elemental Analyser (ThermoFinnigan)Thermogravimetric (TG) and differential scanning

calorimetry (DSC) measurements of 1a were performed instatic air atmosphere under dynamic heating conditionswith a sample weight of 6ndash8 mg and heating rate 5degCminDSC measurements were performed in the range of20ndash400degC on a DSC XP-10 analyser (THASS GmbH) andTG curve was measured between 20ndash500degC on a TGXP-10 instrument (THASS GmbH) To monitor theintermediates of the thermal decay the samples wereprepared in conditions of DSC measurement by dynamicheating up to the selected temperatures with the heatingrate of 5degCmin and consequently analyzed by suitabletechniques The transmission 57Fe Moumlssbauer spectrawere collected at 300 K in a constant acceleration mode


with a 57Co(Rh) source The final decomposition productwas also analyzed at 5 K in zero external magnetic field andat 5 K in an external magnetic field of 5 T applied parallel tothe X-ray direction using a cryomagnetic system of OxfordInstruments The isomer shift values were calibrated againstmetallic α-Fe In-field Moumlssbauer spectra were fitted bymeans of the Lorentzian line shapes using the least squaresmethod featured in the MossWinn computer program FTIR spectra were measured on a Nexus 670 FT-IR (ThermoNicolet) spectrophotometer using KBr pellets in thewavenumber range of 400ndash4000 cmndash1 at temperatures 25150 230 265 and 450degCThe transmission electron microscopy was performed

on a JEOL JEM-2010 instrument (LaB6 cathode acceler-ating voltage of 200 kV point-to-point resolution019 nm) to consider the particle size and structure ofthe final spinel phase A drop of high-purity distilledwater containing the ultrasonically dispersed particleswas placed onto a holey-carbon film supported by acopper-mesh TEM grid and dried in air at roomtemperature

X-ray structure determinations and refinementsX-ray single crystal diffraction experiments for both 1aand 1b were carried out on a four circle κ-axis Xcalibur2diffractometer at 100(2) K equipped with a CCD de-tector Sapphire2 (Oxford Diffraction) The CrysAlis soft-ware package [82] was used for data collection andreduction The structures were solved by the SIR97 pro-gram [83] incorporated within the WinGX programpackage [84] All non-hydrogen atoms of 1a and 1b wererefined anisotropically by the full-matrix least-squaresprocedure [85] with weights w = 1[σ2(Fo

2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo

2 + 2Fc2)3 Hydrogen atoms were found

in the difference Fourier maps nevertheless these weremodeled using a riding model except for thosebelonging to crystal water molecules which parameterswere fixed The structures of 1a and 1b depicted inFigures 1 2 6 and 7 were drawn using the Diamondsoftware [86] X-ray powder diffraction pattern of thefinal decomposition product was recorded using aPANalytical XrsquoPert MPD device (iron-filtered CoKα radi-ation λ = 0178901 nm 40 kV and 30 mA) in Bragg-Brentano geometry and equipped with XrsquoCeleratordetector Powdered sample was spread on zero-background single-crystal Si slides and scanned in con-tinuous mode (resolution of 0017deg 2 Theta scan speedof 0005deg 2 Theta per second) within the angular range10-120o The acquired patterns were processed (iephase analysis and Rietveld refinement) using Xacute PertHighScore Plus software (PANalytical The Netherlands)in combination with PDF-4+ and ICSD databases (ICSDcollection codes are Co3O4 ndash 63165 CoFe2O4 ndash 98553)

Additional files

Additional file 1 Electronic Supplementary Information The filecontains IR spectrum of 1a (Figure S1) and temperature dependences ofthe effective magnetic moment (μeff) and reciprocal molar susceptibility(1χmol) (Additional file 1 Figures S2 and S3)

Additional file 2 A CIF file for complex 1a

Additional file 3 A CIF file for complex 1b

Abbreviationsaed NNrsquo-bis(3-aminopropyl)-ethylenediamine bipy 2-(pyridin-2-yl)pyridine =220-bipyridine bipy2 4-(pyridin-4-yl)pyridine = 440-bipyridineDSC Differential scanning calorimetry EGA Evolved gas analysisen Ethylenediamine = ethane-12-diamine DMF NNrsquo-dimethylformamideIR Infrared ox Oxalate PBA Prussian blue analogue TEM Transmissionelectron microscopy terpy 26-di(pyridin-2-yl)pyridine = 2206020-terpyridineTG Thermogravimetry tren Tris(2-aminoethyl)amine XRD X-ray powderdiffraction

Competing interestsThe authors declare that they have no competing interests

Authorsrsquo contributionsMMM synthesized all samples and made substantial contributions to thedata collection and analysis BD made substantial contributions to the surveyresults data analysisinterpretation and drafting the manuscript ZTperformed single-crystal diffraction experiments and calculations andtogether with RZ participated in the overall data interpretations and wereinvolved in drafting the manuscript BD ZT RZ and JČ revised themanuscript for the intellectual content All authors read and approved thefinal version of the manuscript

AcknowledgementsThe authors gratefully thank the Operational Program Research andDevelopment for Innovations - European Regional Development Fund(CZ1052100030058) Operational Program Education for Competitiveness-European Social Fund (CZ1072300200017) of the Ministry of EducationYouth and Sports of the Czech Republic The authors also acknowledge thefinancial support from the Grant Agency of the Czech Republic (Grant NoP207110841) We also thank to J Filip for XRD experiments data and to LMachala and J Čuda for the fitting of Moumlssbauer spectra JČ thanks grantAPVV-0014-11 for partial financial support

Author details1Regional Centre of Advanced Technologies and Materials amp Department ofInorganic Chemistry Palackyacute University Tř 17 listopadu 12 OlomoucCZ-77146 Czech Republic 2Regional Centre of Advanced Technologies andMaterials amp Department of Physical Chemistry Palackyacute University Tř 17listopadu 12 Olomouc CZ-77146 Czech Republic 3Department of InorganicChemistry Institute of Chemistry Faculty of Sciences PJ Šafaacuterik University inKošice Moyzesova 11 Košice SK-041 54 Slovakia

Received 15 November 2012 Accepted 28 January 2013Published 8 February 2013

References1 Verdaguer M Girolami GS Miller JS Drillon M Magnetic Prussian Blue

Analogs In Magnetism Molecules to Materials Volume 5 Weinheim Wiley-VCH Verlag GmbH amp Co KGaA 2005

2 Catala L Volatron F Brinzei D Mallah T Functional CoordinationNanoparticles Inorg Chem 2009 483360ndash3370

3 Ricci F Palleschi G Sensor and biosensor preparation optimisation andapplications of Prussian Blue modified electrodes Biosens Bioelectron2005 21389ndash407

4 Jayalakshmi M Scholz FJ Performance characteristics of zinchexacyanoferratePrussian blue and copper hexacyanoferratePrussianblue solid state secondary cells J Power Sources 2000 91(2)217ndash223


5 Hu B Fugetsu B Yu H Abe Y Prussian blue caged in spongiformadsorbents using diatomite and carbon nanotubes for elimination ofcesium J Hazard Mater 2012 217ndash21885ndash91

6 Okubo M Asakura D Mizuno Y Kim JD Mizokawa T Kudo T Honma ISwitching Redox-Active Sites by Valence Tautomerism in Prussian BlueAnalogues AxMny[Fe(CN)6]nH2O (A K Rb) Robust Frameworks forReversible Li Storage J Phys Chem Lett 2010 12063ndash2071

7 Uemura T Ohba M Kitagawa S Size and Surface Effects of Prussian BlueNanoparticles Protected by Organic Polymers Inorg Chem 2004437339ndash7345

8 Liang C Liu P Xu J Wang H Wang W Fang J Wang Q Shen W Zhao JA Simple Method for the Synthesis of Fe-Co Prussian Blue Analoguewith Novel Morphologies Different Structures and Dielectric PropertiesSynth React Inorg Met-Org Nano-Met Chem 2011 41(9)1108

9 Koncki R Chemical Sensors and Biosensors Based on Prussian BluesCrit Rev Anal Chem 2002 3279ndash96

10 DeLongchamp DM Hammond PT Multiple-Color Electrochromism fromLayer-by-Layer-Assembled PolyanilinePrussian Blue NanocompositeThin Films Chem Mater 2004 164799ndash4805

11 Bustos L Godinez LA Modified Surfaces with Nano-StructuredComposites of Prussian Blue and Dendrimers New Materials forAdvanced Electrochemical Applications Int J Electrochem Sci 2011 61ndash36

12 de Tacconi NR Rajeshwar K Metal Hexacyanoferrates Electrosynthesis inSitu Characterization and Applications Chem Mater 2003 153046ndash3062

13 Verdaguer M Bleuzen A Marvaud V Vaissermann J Seuleiman MDesplanches C Scuiller A Train C Garde R Gelly G Lomenech C RosenmanI Veillet P Cartier C Villain F Molecules to build solids high TC molecule-based magnets by design and recent revival of cyano complexeschemistry Coord Chem Rev 1999 1921023ndash1047

14 Dunbar KR Heintz RA Chemistry of Transition Metal CyanideCompounds Modern Perspectives In Progress in Inorganic ChemistryVolume 45 New York Karlin KD John Wiley 2007283ndash391

15 Herrera JM Bachschmidt A Villain F Bleuzen A Marvaud V Wernsdorfer WVerdaguer M Mixed valency and magnetism in cyanometallates andPrussian blue analogues Phil Trans R Soc A 2008 366127ndash138

16 Sato O Optically Switchable Molecular Solids Photoinduced Spin-Crossover Photochromism and Photoinduced Magnetization Acc ChemRes 2003 36692ndash700

17 Talham DR Meisel MW Thin films of coordination polymer magnetsChem Soc Rev 2011 403356ndash3365

18 Holmes SM Girolami GS Solndashgel Synthesis of KVII[CrIII(CN)6]2H2OA Crystalline Molecule-Based Magnet with a Magnetic OrderingTemperature above 100degC J Am Chem Soc 1999 1215593ndash5594

19 Sato O Photoinduced magnetization in molecular compoundsJ Photochem and Photobiol C Chem 2004 5203ndash223

20 Sato O Tao J Zhang YZ Control of Magnetic Properties through ExternalStimuli Angew Chem Int Ed 2007 462152ndash2187

21 Culp JT Park JH Frye F Huh YD Meisel MW Talham DR Magnetism ofmetal cyanide networks assembled at interfaces Coord Chem Rev 20052492642ndash2648

22 Bleuzen A Lomenech C Escax V Villain F Varret F Cartier dit Moulin CVerdaguer M Photoinduced Ferrimagnetic Systems in Prussian BlueAnalogues CIxCo4[Fe(CN)6]y (C

I = Alkali Cation) 1 Conditions to Observethe Phenomenon J Am Chem Soc 2000 1226648ndash6652

23 Sato O Einaga Y Fujishima A Hashimoto K Photoinduced Long-RangeMagnetic Ordering of a Cobalt-Iron Cyanide Inorg Chem 1999384405ndash4412

24 Ohba M Okawa H Synthesis and magnetism of multi-dimensionalcyanide-bridged bimetallic assemblies Coord Chem Rev 2000198313ndash328

25 Colacio E Ghazi M Stoeckli-Evans H Lloret F Moreno JM Perez C Cyano-Bridged Bimetallic Assemblies from Hexacyanometalate [M(CN)6]3-(M =MnIII and FeIII) and [M(N4-macrocycle)]2+ (M = FeIII NiII and ZnII)Building Blocks Syntheses Multidimensional Structures and MagneticProperties Inorg Chem 2001 404876ndash4883

26 Marvaud V Decroix C Scuiller A Guyard-Duhayon C Vaissermann J GonnetF Verdaguer M Hexacyanometalate Molecular Chemistry HeptanuclearHeterobimetallic Complexes Control of the Ground Spin State Chem EurJ 2003 91677ndash1691

27 Funck KE Hilfiger MG Berlinguette CP Shatruk M Wernsdorfer W DunbarKR Trigonal-Bipyramidal Metal Cyanide Complexes A Versatile Platform

for the Systematic Assessment of the Magnetic Properties of PrussianBlue Materials Inorg Chem 2009 483438ndash3452

28 Newton GN Nihei M Oshio H Cyanide-Bridged Molecular Squares ndash TheBuilding Units of Prussian Blue Eur J Inorg Chem 2011 203031ndash3042

29 Černaacutek J Orendaacuteč M Potočňaacutek I Chomič J Orendaacutečovaacute A Skoršepa JFeher A Cyanocomplexes with one-dimensional structurespreparations crystal structures and magnetic properties Coord ChemRev 2002 22451ndash66

30 Billing R Optical and photoinduced electron transfer in ion pairs ofcoordination compounds Coord Chem Rev 1997 159257ndash270

31 Billing R Vogler A Optical and photoinduced electron transfer in tris(ethylenediamine)cobalt(III)-cyanometallate ion pairs J PhotochemPhotobiol A Chem 1997 103(3)239ndash247

32 Poulopoulou VG Li ZW Taube H Comparison of the rates of substitutionin [Ru(NH3)5H2O]

3+ and [Os(NH3)5H2O]3+ by hexacyano complexes

substitution coupled to electron transfer Inorg Chim Acta 1994225173ndash184

33 Allen FH Bellard S Brice MD Cartwright BA Doubleday A Higgs HHummelink T Hummelink-Peters BG Kennard O Motherwell WDS RodgersJR Watson DG Cambridge Structural Database System (CSDS) CambridgeUK 1994

34 Bernhardt PV Bozoglian F Macpherson BP Martinez M Molecular mixed-valence cyanide bridged CoIIIndashFeII complexes Coord Chem Rev 20052491902ndash1916

35 Bernhardt PV Bozoglian F Gonzalez G Martınez M Macpherson BP SienraB Dinuclear Cyano-Bridged CoIII-FeII Complexes as Precursors forMolecular Mixed-Valence Complexes of Higher Nuclearity Inorg Chem2006 4574ndash82

36 Bernhardt PV Martınez M Rodrıguez C Molecular CoIIIFeII Cyano-BridgedMixed-Valence Compounds with High Nuclearities and Diversity of CoIII

Coordination Environments Preparative and Mechanistic AspectsInorg Chem 2009 484787ndash4797

37 Seitz K Peschel P Babel D On the Crystal Structure of the CyanidoComplexes [Co(NH3)6][Fe(CN)6] [Co(NH3)6]2[Ni(CN)4]3sdot 2H2O [Cu(en)2][Ni(CN)4] Z Anorg Allg Chem 2001 627929ndash934

38 Bok LD Leipoldt JG Basson SS The crystal structure of tris(ethylenediamine) cobalt(III) hexacyanoferrate(III)dihydrate Co(C2H8N2)3[Fe(CN)6]2 middot H2O Z Anorg Allg Chem 1972 389307ndash314

39 Elder RC Kennard GJ Payne MD Deutsch F Synthesis andCharacterization of Bis(ethylenediamine)cobalt(III) Complexes ContainingChelated Thioether Ligands Crystal Structures of [(en)2Co(S(CH3)CH2CH2NH2)][Fe(CN)6] and [(en)2Co(S(CH2C6H5)CH2COO)](SCN)2Inorg Chem 1978 171296ndash1303

40 Maľarovaacute M Traacutevniacuteček Z Zbořil R Černaacutek J [Co(en)3][Fe(CN)6]sdot H2O and[Co(en)3][Fe(CN)6] A dehydration process investigated by single crystalX-ray analysis thermal analysis and Moumlssbauer spectroscopyPolyhedron 2006 252935ndash2943

41 Matikovaacute-Maľarovaacute M Černaacutek J Massa W Varret F Three Co(III)ndashFe(II)complexes based on hexacyanoferrates Syntheses spectroscopic andstructural characterizations Inorg Chim Acta 2009 362443ndash448

42 Ohashi Y Yanagi K Mitsuhashi Y Nagata K Kaizu Y Sasada Y Kobayashi HAbsolute Configuration of (minus)D-Tris(220-bipyridine)cobalt(III) J Am ChemSoc 1979 1014739ndash4740

43 Yanagi K Ohashi Y Sasada Y Kaizu Y Kobayashi H Crystal structure andAbsolute Configuration of (minus)589-Tris(220-bipyridine)cobalt(III)Hexacyanoferrate(III) Octahydrate Bull Chem Soc Jpn 1981 54118ndash126

44 Singh N Diwan K Drew MGB Supramolecular assemblies of metal ions incomplex bimetallic and trimetallic salts based on hexacyanoferrate(III)ion Polyhedron 2010 293192ndash3197

45 Zhuge F Wu B Yang J Janiak C Tang N Yang XJ Microscale hexagonalrods of a charge-assisted second-sphere coordination compound[Co(DABP)3][Fe(CN)6] Chem Commun 2010 461121ndash1123

46 Ulas G Brudvig GW Redirecting Electron Transfer in Photosystem II fromWater to Redox-Active Metal Complexes J Am Chem Soc 201113313260ndash13263

47 Kersting B Siebert D Volkrner D Kolm MJ Janiak C Synthesis andCharacterization of Homo- and Heterodinuclear Complexes Containing theN3M(μ2-SR)3MN3 Core (M= Fe Co Ni) Inorg Chem 1999 383871ndash3882

48 Mohai B Thermolysis of cyano complexes VII On the thermaldecomposition of hexacyanocobaltate(III) ligand exchange duringthermolysis Z Anorg Allg Chem 1972 392287ndash294


49 Horvaacuteth A Mohai B Thermolysis of complex cyanides - XIII Structuraltransformations at thermal decomposition of [M(en)3][Mrsquo(CN)5NO]double complexes J Inorg Nucl Chem 1980 42195ndash199

50 Ng CW Ding J Gan LM Microstructural Changes Induced by ThermalTreatment of Cobalt(II) Hexacyanoferrate(III) Compound J Solid StateChem 2001 156400ndash407

51 Ng CW Ding J Shi Y Gan LM Structure and magnetic properties ofcopper(II) hexacyanoferrate(III) compound J Phys Chem Solids 200162767ndash775

52 Pechenyuk SI Domonov DP Gosteva AN Kadyrova GI Kalinnikov VTSynthesis Properties and Thermal Decomposition of Compounds[Co(En)3][Fe(CN)6] middot 2H2O and [Co(En)3]4[Fe(CN)6]3 middot 15H2O Russ J CoordChem 2012 38596ndash603

53 Kaupp G Solid-state reactions dynamics in molecular crystals Curr OpinSolid State Mater Sci 2002 6131ndash138

54 Nicketic SR Rasmussen K Conformational Analysis of CoordinationCompounds IV Tris(12-ethanediamine)- and Tris(23-butanediamine)cobalt(III) complexes Acta Chem Scand 1978 A32391ndash400

55 Matsuki R Shiro M Asahi T Asai H Absolute configuration of Λ-(+)589-tris(ethylenediamine)cobalt(III) triiodide monohydrate Acta CrystallogrSect E Struct Rep Online 2001 57m448ndashm450

56 Ueda T Bernard GM McDonald R Wasylishen RE Cobalt-59NMR and X-raydiffraction studies of hydrated and dehydrated (plusmn)-tris(ethylenediamine)cobalt(III) chloride Solid State Nucl Magn Reson 2003 24163ndash183

57 Moron MC Palacio F Pons J Casabo J Solans X Merabet KE Huang D ShiX Teo BK Carlin RL Bimetallic Derivatives of [M(en)3I

3+ Ions (M = Cr Co)An Approach to Intermolecular Magnetic Interactions in MolecularMagnets Inorg Chem 1994 33746ndash753

58 Saha MK Lloret F Bernal I Inter-String Arrays of Bimetallic Assemblieswith Alternative Cu2+-Cl-Cu2+ and Cu-NC-M (M = Co3+ Fe+3 Cr+3)Bridges Syntheses Crystal Structure and Magnetic Properties InorgChem 2004 431969ndash1975

59 Salah El Fallah M Rentschler E Caneschi A Sessoli R Gatteschi D A Three-Dimensional Molecular Ferrimagnet Based on Ferricyanide and [Ni(tren)]2+

Building Blocks Angew Chem Int Ed Engl 1996 351947ndash194960 Herchel R Tuček J Traacutevniacuteček Z Petridis D Zbořil R Crystal Water Molecules

as Magnetic Tuners in Molecular Metamagnets Exhibiting Antiferro-Ferro-Paramagnetic Transitions Inorg Chem 2011 509153ndash9163

61 Reguera E Feacuternandez-Bertraacuten J Effect of the water of crystallization onthe Moumlssbauer spectra of hexacyanoferrates (II and III) Hyperfine Interact1994 8849ndash58

62 Nakamoto I Infrared Spectra of Inorganic and Coordination Compounds NewYork John Wiley and Sons 2002

63 Landolt-Bornstein GII Atomic and Molecular Physics Volume 2 VerlagSpringer 1966

64 Comba P Prediction and Interpretation of EPR Spectra of Low-Spin Iron(III)Complexes with the MM-AOM Method Inorg Chem 1994 334511ndash4583

65 Tang HY Lin HY Wang MJ Liao MY Liu JL Hsu FC Wu MK Crystallizationand Anisotropic Properties of Water-Stabilized Potassium Cobalt OxidesChem Mater 2005 172162ndash2164

66 Viertelhaus M Henke H Anson CE Powell AK Solvothermal Synthesis andStructure of Anhydrous Manganese(II) Formate and Its TopotacticDehydration from Manganese(II) Formate Dihydrate Eur J Inorg Chem2003 122283ndash2289

67 Song Y Zavalij PY Suzuki M Whittingham MS New Iron(III) PhosphatePhases Crystal Structure and Electrochemical and Magnetic PropertiesInorg Chem 2002 415778ndash5786

68 Greve J Jess I Nather C Synthesis crystal structures and investigationson the dehydration reaction of the new coordination polymers poly[diaqua-(μ2-squarato-O Orsquo)-(μ2ndash440-bipyridine-N Nrsquo)Me(II)] hydrate(Me = Co Ni Fe) J Sol State Chem 2003 175328ndash340

69 Feist M Troyanov SI Mehner H Witke K Kemnitz E Halogeno Metallates ofTransition Elements with Cations of Nitrogen-containing HeterocyclicBases VII Two Oxidation States and Four Different Iron Coordinations inone Compound Synthesis Crystal Structure and SpectroscopicCharacterization of 14-Dimethylpiperazinium Chloroferrate (IIIII)(dmpipzH2)6[Fe

IICl4]2 [FeIIICl4]2[Fe

IICl5] [FeIIICl6] Z Anorg Allg Chem 1999

625141ndash14670 Wyrzykowski D Maniecki T Pattek-Janczyk A Stanek J Warnke Z Thermal

analysis and spectroscopic characteristics of tetrabutylammoniumtetrachloroferrate(III) Thermochim Acta 2005 43592ndash98

71 Roodburn HM Fisher JR Reaction of Cyanogen with Organic CompoundsX Aliphatic and Aromatic Diamines J Org Chem 1957 22895ndash899

72 Zsakoacute J Pokol G Novaacutek C Vaacuterhelyi C Doboacute A Liptay G KINETIC ANALYISOF TG DATA XXXV Spectroscopic and thermal studies of some cobalt(III)chelates with ethylenediamine J Therm Anal Calorim 2001 64843ndash856

73 Nihei M Sekine Y Suganami N Nakazawa K Nakao A Nakao H Murakami YOshio H Controlled Intramolecular Electron Transfers in Cyanide-BridgedMolecular Squares by Chemical Modifications and External Stimuli J AmChem Soc 2011 1333592ndash3600

74 Sakai T Ohgo Y Hoshino A Ikeue T Saigon T Takahashi M Nakanuta MElectronic Structures of Five-Coordinate Iron(III) Porphyrin Complexeswith Highly Ruffled Porphyrin Ring Inorg Chem 2004 435034ndash5043

75 Fejitha KS Mathew S Thermoanalytical investigations of tris(ethylenediamine)nickel(II) oxalate and sulphate complexes J Therm AnalCalorim 2010 102931ndash939

76 Persoons RM Degrave E Van Denberghe RE Moumlssbauer study ofCo-substituted magnetite Hyperfine Interact 1990 54655ndash660

77 Haneda K Morrish AH Noncollinear magnetic structure of CoFe2O4 smallparticles J Appl Phys 1988 634258ndash4261

78 Greenwood NN Gibb TC Moumlssbauer spectroscopy New York Barnes andNoble Inc 1971

79 Fedotova YA Baev VG Lesnikovich AI Milevich IA Vorobeva SA MagneticProperties and Local Configurations of 57Fe Atoms in CoFe2O4 Powdersand CoFe2O4PVA Nanocomposites Phys Sol State 2011 53647ndash653

80 Ngo AT Bonville P Pileni MP Nanoparticles of CoxFey_zO4 Synthesis andsuperparamagnetic properties Eur Phys J 1999 B9583ndash592

81 Vivier V Aguey F Fournier J Lambert JF Bedioui F Che M Spectroscopicand Electrochemical Study of the Adsorption of [Co(en)2Cl2]Cl on γ-Alumina Influence of the Alumina Ligand on Co(III)(II) Redox PotentialJ Phys Chem B 2006 110900ndash906

82 Diffraction O CrysAlis CCD Abingdon England Oxford Diffraction Ltd 200683 Altomare A Burla MC Camalli M Cascarano GL Giacovazzo C Guagliardi A

Moliterni AGG Polidori G Spagna R SIR97 a new tool for crystal structuredetermination and refinement J Appl Cryst 1999 32115ndash119

84 Farrugia LJ WinGX suite for small-molecule single-crystal crystallographyJ Appl Cryst 1999 32837ndash838

85 Sheldrick GM A short history of SHELX Acta Crystallogr Sect A FoundCrystallogr 2008 64112ndash122

86 Brandenburg K DIAMOND Visual Crystal Structure Information System Version21e Bonn Germany Crystal Impact GbR 2000

doi1011861752-153X-7-28Cite this article as Traacutevniacuteček et al Thermal decomposition of [Co(en)3][Fe(CN)6]∙ 2H2O Topotactic dehydration process valence and spinexchange mechanism elucidation Chemistry Central Journal 2013 728

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Abstract

Background

Results

Conclusions

Background

Results and discussion

Synthesis X-ray structure and spectral characterization of [Co(en)3][Fe(CN)6]middot 2H2O (1a)

Thermal behavior of [Co(en)3][Fe(CN)6]∙ 2H2O (1a) ndash a general overview

Chemical structural and spectral characterization of [Co(en)3][Fe(CN)6]∙12H2O (1b) formed in the first decomposition step

Chemical structural and spectral characterization of the intermediates formed during the second and third decomposition steps

Chemical structural and spectral characterizations of the intermediates formed in the fourth decomposition step

Characterization of the final decomposition product ndash the fifth decomposition step

Conclusions

Experimental

Materials and reagents

Synthesis

Physical measurements

X-ray structure determinations and refinements

Additional files

Abbreviations

Competing interests

Authorsrsquo contributions

Acknowledgements

Author details

References

Traacutevniacuteček et al Chemistry Central Journal 2013 728 of 18httpjournalchemistrycentralcomcontent7128

BackgroundTransition metal hexacyanido complexes represent anenormous and well-known group of coordination spe-cies The Prussian blue with the idealized formula Fe4[Fe(CN)6]3 middot nH2O is one of the oldest examples of ahexacyanido complex combining interesting structuralfeatures and magnetic properties Therefore manyPrussian blue analogues [1] eg MxA[B(CN)6]z middot nH2O(M is alkali metal A and B are different divalenttriva-lent transition metals x le 1 z le 1 if z lt 1 B-sites are frac-tionally occupied and B-vacancies are present) have beenextensively studied due to their sorption ion-exchangeelectron transfer or magnetic properties and in recentyears many applications using PBAs usually in form ofthin films or nanoparticles have been developed [23]The reversible intercalation of alkali metal cations due

to the zeolite-like structure of PBAs [4] has beenemployed in still active development of the selective ad-sorbent of 137Cs from radioactive waste waters [5] or morerecently in construction of a new active electrode materialfor Li-ion batteries (AxMny[Fe(CN)6] where A = K Rbx lt 1 1 lt y lt 15) [6] The electrochemical coating ofelectrodes with thin film of PBAs or deposition withcoordinated PBAs nanoparticles [278] gave rise a largenumber of amperometric and potentiometric sensors fornon-electroactive ions or H2O2 [39] electrochromicsensors [10] or biosensors [11] The electrochromic orthermochromic behavior of electrochemically preparedPBAs thin films was further applied in the construction ofdifferent devices including electrochromic displays andpattering devices thermal probes or photoelectrochem-icalphotocatalytical solar energy convertors [12]PBAs also represent an enormous and important

group of molecular magnets [113-15] which play im-portant roles in many applications mainly in molecularelectronics and magneticelectronic devices [1617] Dur-ing the experimental race to enhance the Curietemperatures of molecular magnets based on PBAs thesystems incorporating V(II) gave the most promisingresults and KV[Cr(CN)6]middot2H2O was found to possess thehighest Tc even above the boiling point of water (376 K)[18] This invention of room temperature molecule-based magnets opens interesting applications as mag-netic switches oscillators or magneto-optical datastorage devices The cyanido-bridged networks servingas a platform for the preparation of coordinationnanoparticles based on Prussian blue has also beenemployed for the controllingtuning of magnetism bytemperature (eg AI[MIIMIII(CN)6] A = alkali metal ion)[2] or light irradiation (with a general formula of AxCoy[Fe(CN)6]z middot nH2O x y z are independent) [8]An important feature of especially Co-Fe Prussian blue

systems is the phenomenon of photoinduced magnetiza-tion or photoreversible enhancement of magnetization

[19-21] which has been observed in eg Rb18CoIII33Co

II07

[FeII(CN)6]33 middot 13H2O [2223] Na034Co133[Fe(CN)6] middot45H2O [19] or K04Co14[Fe(CN)6] middot 5H2O [20] Thesecompounds are efficient 3D-ferrimagnets at lowtemperatures (Tc lt 30 K) due to the presence of majorityof FeIIndashCNndashCoIII diamagnetic pairs which undergo uponirradiation photoinduced electron transfer resulting inparamagnetic FeIIIndashCNndashCoII species Such transform-ation is accompanied by elongation of the CondashN bondlengths (015ndash020 Aring) which is possible only in the caseof flexible inorganic network provided by the existenceof hexacyanidoferrate vacancies occupied by watermoleculesTransition metal hexacyanido complexes have been

also successfully utilized as building blocks for con-structing oligo- and polynuclear assemblies derived fromthe Prussian blue and a large number of such organicndashinorganic hybrid materials containing various organicligands mainly N-donor linear or macrocyclic ligandshave been extensively studied [24-28] These compoundswere also found to behave as molecular magnets [29]with potential applications as molecular devices ormemory devices Some of them also revealed very spe-cific optical properties including ion pair charge-transfer(IPCT) [30] transitions corresponding to the transfer ofelectrons from the complex anions to the complex cationsin the visible and near-ultraviolet spectral regions Thisphenomenon was confirmed for ionic pair compoundsinvolving both [Co(en)3]

3+ and [M(CN)x]4ndash (for x = 6

M = Fe Ru Os for x = 8 M =Mo W) complex ions [31]An irradiation of solutions containing these species intothe IPCT absorption band (λirr = 405 or 510 nm) leads to astructure re-arrangement and the formation of bi- ortrinuclear species For the ionic pairs [M(NH3)5L]

3+ and[Fe(CN)6]

3ndash (M = Ru Os L =NH3 or H2O) an inverse dir-ection of the electron transfer of the IPCT transition(from the cation to the anion) was found [32]Only eleven X-ray structures of discrete dinuclear

Co-Fecyanido-bridged complexes have been reported upto now whereas about ninety hits corresponding to poly-or oligomeric Co-Fe cyanido-bridged complexes have beendeposited within the Cambridge Structural Database upto now [33] Most of the dinuclear complexes have thegeneral formula of [LnCo

IIIndashNCndashFeII(CN)5]ndash where

Ln stands for a macrocyclic ligand and they have beensystematically studied by Bernhardt et al [34-36] Up todate similar number of ionic pair Co(III)-Fe(III)complexes have been structurally characterized Theyalways contain hexacyanidoferrate(III) anion and Co(III)complexed by ammonia [37] en [38-41] bipy [42-45] terpy[46] or other suitable ligands [47] Despite Co(III)-Fe(III)hexacyanidoferrates represent very important groupof compounds bearing a broad spectrum of importantphysico-chemical properties surprisingly only a little









3+


















1a 1b





Unit cell dimension

a [Aring] 82822(2) 150448(3)

b [Aring] 165364(3) 84631(2)

c [Aring] 145365(3) 149812(3)

β [deg] 91988(2) 90160(2)

Z 4 2

V[Aring3] 198969(7) 190748(7)


T [K] 100 100

μ [mmndash1] 1599 1658










R1 = 00263wR2 = 00796


R1 = 00333wR2 = 00949



1a 1b




































3ndash anions



1a

O1ndashH1V O2 092 199 1768 2905(2)

O1ndashH1W N3 100 208 1638 3050(3)

O2ndashH2V N3Ai 101 183 1616 2807(3)

O2ndashH2W N2i 077 212 1639 2862(3)

N7ndashH7D O2 092 200 1592 2882(3)

N7ndashH7C N1 092 208 1591 2960(3)

N8ndashH8C N1Aiii 092 235 1368 3083(3)

N9ndashH9D N2Aiii 092 255 1303 3227(3)

N9ndashH9D N2i 092 244 1406 3205(3)

N10ndashH10C N3ii 092 235 1532 3203(3)

N10ndashH10D N2A 092 242 1455 3226(3)

N11ndashH11C N3ii 092 215 1580 3019(3)

N11ndashH11D N2i 092 235 1453 3153(3)

N12ndashH12C N1 092 239 1510 3227(3)

N12ndashH12D N2A 092 208 1653 2976(3)

1b

O1ndashH1W N3i 120 167 1393 2695(7)

N4ndashH4C N2Aiii 092 212 1594 2997(3)

N5ndashH5C N1Aiv 092 220 1514 3039(3)

N5ndashH5D O1 092 193 1467 2742(7)

N6ndashH6C N1 092 232 1431 3108(3)

N6ndashH6D N1A 092 243 1371 3168(3)

N7ndashH7C N2Aiii 092 219 1459 2996(3)

N7ndashH7D N3i 092 220 1569 3069(4)

N8ndashH8D N3 092 219 1480 3015(4)

N9ndashH9C N1v 092 231 1437 3102(3)

N9ndashH9D N2ii 092 206 1488 2887(3)























2 240 HS Fe(II) 117 225 ndash




3 300 HS Fe(II) 114 249 ndash
















N C H




114

100






100 0 0 0 CoFe2O4 (SP)

468 0 0 0 CoFe2O4 (SP)

532 CoFe2O4

34 0 0 0 CoFe2O4 (SP)

791 CoFe2O4

175 CoFe2O4

ive abundance











FeIII[CoII(CN)5]

12 CoFe2O4 + 16 Co3O4

-32 H2O

-12 H2O

-(en + CN)

en + 12 (CN)2

NH

N HN

N Exo (max 208degC)

Endo (min 214degC)

Exo (max 354degC)

Exo (max 354degC)

Endo (min 80degC)

+ O2 -(NH2) NOx + H2O

-2 H2NCH2CH3

+ O2 -5 (CN)

step I

step II

step III

step IV

step V

Fe

N

N

N

N

Co

CN

CN

CN

CN

Fe CoH2N

H2N

CN

CN

CN

CO2NOxH2O

+ O2

CO2 + N2

(1a)

(1b)

NC

NC

NC






































T-site 038 minus002 526 054

O-site 054 minus008 490 063









001s)



45 0579 302 303

55 0589 304











2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo



Additional files




















































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References









3+


















1a 1b





Unit cell dimension

a [Aring] 82822(2) 150448(3)

b [Aring] 165364(3) 84631(2)

c [Aring] 145365(3) 149812(3)

β [deg] 91988(2) 90160(2)

Z 4 2

V[Aring3] 198969(7) 190748(7)


T [K] 100 100

μ [mmndash1] 1599 1658










R1 = 00263wR2 = 00796


R1 = 00333wR2 = 00949



1a 1b




































3ndash anions



1a

O1ndashH1V O2 092 199 1768 2905(2)

O1ndashH1W N3 100 208 1638 3050(3)

O2ndashH2V N3Ai 101 183 1616 2807(3)

O2ndashH2W N2i 077 212 1639 2862(3)

N7ndashH7D O2 092 200 1592 2882(3)

N7ndashH7C N1 092 208 1591 2960(3)

N8ndashH8C N1Aiii 092 235 1368 3083(3)

N9ndashH9D N2Aiii 092 255 1303 3227(3)

N9ndashH9D N2i 092 244 1406 3205(3)

N10ndashH10C N3ii 092 235 1532 3203(3)

N10ndashH10D N2A 092 242 1455 3226(3)

N11ndashH11C N3ii 092 215 1580 3019(3)

N11ndashH11D N2i 092 235 1453 3153(3)

N12ndashH12C N1 092 239 1510 3227(3)

N12ndashH12D N2A 092 208 1653 2976(3)

1b

O1ndashH1W N3i 120 167 1393 2695(7)

N4ndashH4C N2Aiii 092 212 1594 2997(3)

N5ndashH5C N1Aiv 092 220 1514 3039(3)

N5ndashH5D O1 092 193 1467 2742(7)

N6ndashH6C N1 092 232 1431 3108(3)

N6ndashH6D N1A 092 243 1371 3168(3)

N7ndashH7C N2Aiii 092 219 1459 2996(3)

N7ndashH7D N3i 092 220 1569 3069(4)

N8ndashH8D N3 092 219 1480 3015(4)

N9ndashH9C N1v 092 231 1437 3102(3)

N9ndashH9D N2ii 092 206 1488 2887(3)























2 240 HS Fe(II) 117 225 ndash




3 300 HS Fe(II) 114 249 ndash
















N C H




114

100






100 0 0 0 CoFe2O4 (SP)

468 0 0 0 CoFe2O4 (SP)

532 CoFe2O4

34 0 0 0 CoFe2O4 (SP)

791 CoFe2O4

175 CoFe2O4

ive abundance











FeIII[CoII(CN)5]

12 CoFe2O4 + 16 Co3O4

-32 H2O

-12 H2O

-(en + CN)

en + 12 (CN)2

NH

N HN

N Exo (max 208degC)

Endo (min 214degC)

Exo (max 354degC)

Exo (max 354degC)

Endo (min 80degC)

+ O2 -(NH2) NOx + H2O

-2 H2NCH2CH3

+ O2 -5 (CN)

step I

step II

step III

step IV

step V

Fe

N

N

N

N

Co

CN

CN

CN

CN

Fe CoH2N

H2N

CN

CN

CN

CO2NOxH2O

+ O2

CO2 + N2

(1a)

(1b)

NC

NC

NC






































T-site 038 minus002 526 054

O-site 054 minus008 490 063









001s)



45 0579 302 303

55 0589 304











2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo



Additional files




















































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References










1a 1b





Unit cell dimension

a [Aring] 82822(2) 150448(3)

b [Aring] 165364(3) 84631(2)

c [Aring] 145365(3) 149812(3)

β [deg] 91988(2) 90160(2)

Z 4 2

V[Aring3] 198969(7) 190748(7)


T [K] 100 100

μ [mmndash1] 1599 1658










R1 = 00263wR2 = 00796


R1 = 00333wR2 = 00949



1a 1b




































3ndash anions



1a

O1ndashH1V O2 092 199 1768 2905(2)

O1ndashH1W N3 100 208 1638 3050(3)

O2ndashH2V N3Ai 101 183 1616 2807(3)

O2ndashH2W N2i 077 212 1639 2862(3)

N7ndashH7D O2 092 200 1592 2882(3)

N7ndashH7C N1 092 208 1591 2960(3)

N8ndashH8C N1Aiii 092 235 1368 3083(3)

N9ndashH9D N2Aiii 092 255 1303 3227(3)

N9ndashH9D N2i 092 244 1406 3205(3)

N10ndashH10C N3ii 092 235 1532 3203(3)

N10ndashH10D N2A 092 242 1455 3226(3)

N11ndashH11C N3ii 092 215 1580 3019(3)

N11ndashH11D N2i 092 235 1453 3153(3)

N12ndashH12C N1 092 239 1510 3227(3)

N12ndashH12D N2A 092 208 1653 2976(3)

1b

O1ndashH1W N3i 120 167 1393 2695(7)

N4ndashH4C N2Aiii 092 212 1594 2997(3)

N5ndashH5C N1Aiv 092 220 1514 3039(3)

N5ndashH5D O1 092 193 1467 2742(7)

N6ndashH6C N1 092 232 1431 3108(3)

N6ndashH6D N1A 092 243 1371 3168(3)

N7ndashH7C N2Aiii 092 219 1459 2996(3)

N7ndashH7D N3i 092 220 1569 3069(4)

N8ndashH8D N3 092 219 1480 3015(4)

N9ndashH9C N1v 092 231 1437 3102(3)

N9ndashH9D N2ii 092 206 1488 2887(3)























2 240 HS Fe(II) 117 225 ndash




3 300 HS Fe(II) 114 249 ndash
















N C H




114

100






100 0 0 0 CoFe2O4 (SP)

468 0 0 0 CoFe2O4 (SP)

532 CoFe2O4

34 0 0 0 CoFe2O4 (SP)

791 CoFe2O4

175 CoFe2O4

ive abundance











FeIII[CoII(CN)5]

12 CoFe2O4 + 16 Co3O4

-32 H2O

-12 H2O

-(en + CN)

en + 12 (CN)2

NH

N HN

N Exo (max 208degC)

Endo (min 214degC)

Exo (max 354degC)

Exo (max 354degC)

Endo (min 80degC)

+ O2 -(NH2) NOx + H2O

-2 H2NCH2CH3

+ O2 -5 (CN)

step I

step II

step III

step IV

step V

Fe

N

N

N

N

Co

CN

CN

CN

CN

Fe CoH2N

H2N

CN

CN

CN

CO2NOxH2O

+ O2

CO2 + N2

(1a)

(1b)

NC

NC

NC






































T-site 038 minus002 526 054

O-site 054 minus008 490 063









001s)



45 0579 302 303

55 0589 304











2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo



Additional files




















































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References













3ndash anions



1a

O1ndashH1V O2 092 199 1768 2905(2)

O1ndashH1W N3 100 208 1638 3050(3)

O2ndashH2V N3Ai 101 183 1616 2807(3)

O2ndashH2W N2i 077 212 1639 2862(3)

N7ndashH7D O2 092 200 1592 2882(3)

N7ndashH7C N1 092 208 1591 2960(3)

N8ndashH8C N1Aiii 092 235 1368 3083(3)

N9ndashH9D N2Aiii 092 255 1303 3227(3)

N9ndashH9D N2i 092 244 1406 3205(3)

N10ndashH10C N3ii 092 235 1532 3203(3)

N10ndashH10D N2A 092 242 1455 3226(3)

N11ndashH11C N3ii 092 215 1580 3019(3)

N11ndashH11D N2i 092 235 1453 3153(3)

N12ndashH12C N1 092 239 1510 3227(3)

N12ndashH12D N2A 092 208 1653 2976(3)

1b

O1ndashH1W N3i 120 167 1393 2695(7)

N4ndashH4C N2Aiii 092 212 1594 2997(3)

N5ndashH5C N1Aiv 092 220 1514 3039(3)

N5ndashH5D O1 092 193 1467 2742(7)

N6ndashH6C N1 092 232 1431 3108(3)

N6ndashH6D N1A 092 243 1371 3168(3)

N7ndashH7C N2Aiii 092 219 1459 2996(3)

N7ndashH7D N3i 092 220 1569 3069(4)

N8ndashH8D N3 092 219 1480 3015(4)

N9ndashH9C N1v 092 231 1437 3102(3)

N9ndashH9D N2ii 092 206 1488 2887(3)























2 240 HS Fe(II) 117 225 ndash




3 300 HS Fe(II) 114 249 ndash
















N C H




114

100






100 0 0 0 CoFe2O4 (SP)

468 0 0 0 CoFe2O4 (SP)

532 CoFe2O4

34 0 0 0 CoFe2O4 (SP)

791 CoFe2O4

175 CoFe2O4

ive abundance











FeIII[CoII(CN)5]

12 CoFe2O4 + 16 Co3O4

-32 H2O

-12 H2O

-(en + CN)

en + 12 (CN)2

NH

N HN

N Exo (max 208degC)

Endo (min 214degC)

Exo (max 354degC)

Exo (max 354degC)

Endo (min 80degC)

+ O2 -(NH2) NOx + H2O

-2 H2NCH2CH3

+ O2 -5 (CN)

step I

step II

step III

step IV

step V

Fe

N

N

N

N

Co

CN

CN

CN

CN

Fe CoH2N

H2N

CN

CN

CN

CO2NOxH2O

+ O2

CO2 + N2

(1a)

(1b)

NC

NC

NC






































T-site 038 minus002 526 054

O-site 054 minus008 490 063









001s)



45 0579 302 303

55 0589 304











2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo



Additional files




















































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References



1a

O1ndashH1V O2 092 199 1768 2905(2)

O1ndashH1W N3 100 208 1638 3050(3)

O2ndashH2V N3Ai 101 183 1616 2807(3)

O2ndashH2W N2i 077 212 1639 2862(3)

N7ndashH7D O2 092 200 1592 2882(3)

N7ndashH7C N1 092 208 1591 2960(3)

N8ndashH8C N1Aiii 092 235 1368 3083(3)

N9ndashH9D N2Aiii 092 255 1303 3227(3)

N9ndashH9D N2i 092 244 1406 3205(3)

N10ndashH10C N3ii 092 235 1532 3203(3)

N10ndashH10D N2A 092 242 1455 3226(3)

N11ndashH11C N3ii 092 215 1580 3019(3)

N11ndashH11D N2i 092 235 1453 3153(3)

N12ndashH12C N1 092 239 1510 3227(3)

N12ndashH12D N2A 092 208 1653 2976(3)

1b

O1ndashH1W N3i 120 167 1393 2695(7)

N4ndashH4C N2Aiii 092 212 1594 2997(3)

N5ndashH5C N1Aiv 092 220 1514 3039(3)

N5ndashH5D O1 092 193 1467 2742(7)

N6ndashH6C N1 092 232 1431 3108(3)

N6ndashH6D N1A 092 243 1371 3168(3)

N7ndashH7C N2Aiii 092 219 1459 2996(3)

N7ndashH7D N3i 092 220 1569 3069(4)

N8ndashH8D N3 092 219 1480 3015(4)

N9ndashH9C N1v 092 231 1437 3102(3)

N9ndashH9D N2ii 092 206 1488 2887(3)























2 240 HS Fe(II) 117 225 ndash




3 300 HS Fe(II) 114 249 ndash
















N C H




114

100






100 0 0 0 CoFe2O4 (SP)

468 0 0 0 CoFe2O4 (SP)

532 CoFe2O4

34 0 0 0 CoFe2O4 (SP)

791 CoFe2O4

175 CoFe2O4

ive abundance











FeIII[CoII(CN)5]

12 CoFe2O4 + 16 Co3O4

-32 H2O

-12 H2O

-(en + CN)

en + 12 (CN)2

NH

N HN

N Exo (max 208degC)

Endo (min 214degC)

Exo (max 354degC)

Exo (max 354degC)

Endo (min 80degC)

+ O2 -(NH2) NOx + H2O

-2 H2NCH2CH3

+ O2 -5 (CN)

step I

step II

step III

step IV

step V

Fe

N

N

N

N

Co

CN

CN

CN

CN

Fe CoH2N

H2N

CN

CN

CN

CO2NOxH2O

+ O2

CO2 + N2

(1a)

(1b)

NC

NC

NC






































T-site 038 minus002 526 054

O-site 054 minus008 490 063









001s)



45 0579 302 303

55 0589 304











2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo



Additional files




















































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References















2 240 HS Fe(II) 117 225 ndash




3 300 HS Fe(II) 114 249 ndash
















N C H




114

100






100 0 0 0 CoFe2O4 (SP)

468 0 0 0 CoFe2O4 (SP)

532 CoFe2O4

34 0 0 0 CoFe2O4 (SP)

791 CoFe2O4

175 CoFe2O4

ive abundance











FeIII[CoII(CN)5]

12 CoFe2O4 + 16 Co3O4

-32 H2O

-12 H2O

-(en + CN)

en + 12 (CN)2

NH

N HN

N Exo (max 208degC)

Endo (min 214degC)

Exo (max 354degC)

Exo (max 354degC)

Endo (min 80degC)

+ O2 -(NH2) NOx + H2O

-2 H2NCH2CH3

+ O2 -5 (CN)

step I

step II

step III

step IV

step V

Fe

N

N

N

N

Co

CN

CN

CN

CN

Fe CoH2N

H2N

CN

CN

CN

CO2NOxH2O

+ O2

CO2 + N2

(1a)

(1b)

NC

NC

NC






































T-site 038 minus002 526 054

O-site 054 minus008 490 063









001s)



45 0579 302 303

55 0589 304











2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo



Additional files




















































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References











FeIII[CoII(CN)5]

12 CoFe2O4 + 16 Co3O4

-32 H2O

-12 H2O

-(en + CN)

en + 12 (CN)2

NH

N HN

N Exo (max 208degC)

Endo (min 214degC)

Exo (max 354degC)

Exo (max 354degC)

Endo (min 80degC)

+ O2 -(NH2) NOx + H2O

-2 H2NCH2CH3

+ O2 -5 (CN)

step I

step II

step III

step IV

step V

Fe

N

N

N

N

Co

CN

CN

CN

CN

Fe CoH2N

H2N

CN

CN

CN

CO2NOxH2O

+ O2

CO2 + N2

(1a)

(1b)

NC

NC

NC






































T-site 038 minus002 526 054

O-site 054 minus008 490 063









001s)



45 0579 302 303

55 0589 304











2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo



Additional files




















































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References
























T-site 038 minus002 526 054

O-site 054 minus008 490 063









001s)



45 0579 302 303

55 0589 304











2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo



Additional files




















































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References










2) + (00633P)2]for (1a) and w = 1[σ2(Fo

2) + (00605P)2 + 03587P] for(1b) where P = (Fo



Additional files




















































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References






































































































Abstract

Background

Results

Conclusions

Background








Conclusions

Experimental


Synthesis



Additional files

Abbreviations

Competing interests


Acknowledgements

Author details

References

research article open access thermal decomposition of …iii 3.3 ii 0.7 [feii(cn) 6] 3.3 ·13h 2o...

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