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Polyhedron 26 (2007) 1669–1676

Synthesis and structural characterisation of a series of cobaltcomplexes of N-appended anthracenyl cyclam

Simon Boyd, W. David McFadyen *, Brendan F. Abrahams, Martin J. Grannas,Kenneth P. Ghiggino

School of Chemistry, University of Melbourne, Vic. 3010, Australia

Received 18 September 2006; accepted 3 December 2006Available online 8 December 2006

Abstract

The synthesis and structural characterisation of a series of cobalt complexes of 1-(anthracen-9-ylmethyl)-1,4,8,11-tetraazacyclote-tradecane (hereafter L2) is described. The complexes, of the type trans-[CoL2X2]+ in which X = Cl�, NCS� and NO2

� were synthesisedfor their use in photoactivated ligand release studies. X-ray crystal structures show that the macrocycle in all three complexes of the seriesadopts a trans-(III) configuration. Both thiocyanato ligands were found to be N-bound in trans-[CoL2(NCS)2]+ while trans-[CoL2(NO2)2]+ contained both a nitro and nitrito ligand in the one complex. The synthesis of the complex cis-[CoL2(NO2)2]+ fromsodium hexanitrocobaltate(III) is also described. This complex also contains both a nitro and nitrito ligand in the one complex, withthe cyclam in a cis-(V) arrangement about the metal centre.� 2006 Elsevier Ltd. All rights reserved.

Keywords: Anthracene; N-appended cyclam; Cobalt(III) complexes; cis-, trans-isomers; Linkage isomerism

1. Introduction

A considerable range of systems has been developedwhich utilise the electron and energy transfer processesoccurring in linked donor–acceptor molecules for particu-lar applications. The scope of this work encompasses theuse of transition metal complexes and a number of poten-tial uses of metal-based systems are being realised. Fabri-zzi’s group have described several molecular systems inwhich a fluorescent chromophore has been covalentlylinked to a cyclic or open quadridentate ligand [1–7]. Suchsystems can be used for a variety of applications such asmolecular thermometers [1], molecular switches of fluores-cence [2–4] or sensitive metal ion sensors [5–7] when trig-gered by complexation with a transition metal ion. DeRosa et al. describe a range of Cr(III) cyclam complexesin which pendant chromophores could serve as sensitisers

0277-5387/$ - see front matter � 2006 Elsevier Ltd. All rights reserved.

doi:10.1016/j.poly.2006.12.003

* Corresponding author. Tel.: +61 3 8344 4222; fax: +61 3 9347 5180.E-mail address: wdmf@unimelb.edu.au (W.D. McFadyen).

for metal centred photoreactions [8,9]. Complexes involv-ing a coordinated nitrite ligand were found to be capableof photoactivated nitric oxide generation [9]. Compoundsof this type could enable delivery of the biologicallyimportant NO within a well-defined volume when coupledwith a focussed excitation source [9]. We are interested insimilar donor–acceptor complexes containing a Co(III)metal centre coupled to a range of ligands for future usein photoactivated ligand release studies. Towards thisend we have previously described the synthesis and char-acterisation of the ligand 6-(anthracen-9-ylmethyl)-1,4,8,11-tetraazacyclotetradecane (hereafter L1) in whichan anthracene moiety is appended to the apical carbonof the cyclam framework by a methylene bridge (Fig. 1)[10]. Subsequent metallation with cobalt was alsodescribed to yield the complex trans-[CoL1Cl2]+ and someof its photochemical properties were examined. Excitationof a solution of the complex in DMF led to spectralchanges consistent with substitutions at the Co(III) centre[10].

Fig. 1. Structures of the L1 and L2 ligands.

1670 S. Boyd et al. / Polyhedron 26 (2007) 1669–1676

With a view to further developing these ideas, and tobetter understand the photochemistry of donor–acceptorcomplexes containing cobalt(III) as the acceptor group,we have prepared a series of cobalt(III) complexes of1-(anthracen-9-ylmethyl)-1,4,8,11-tetraazacyclotetradecane(hereafter L2) in which anthracene (the donor) is appendedto a nitrogen atom of the cyclam macrocycle (Fig. 1). Thecomplexes are of the type trans-[CoL2X2]+ in whichX ¼ Cl�, NCS�, and NO2

�. These anionic ligands werechosen to cover a broad range of the spectrochemical seriesand it is these ligands that may be lost following a photo-induced process, with the cobalt atom remaining bound tothe cyclam macrocycle. Investigation of complexes of L2

will also allow comparison of the photochemical propertiesof these N-appended complexes with those of their C-appended analogues derived from L1. In this paper wedescribe the synthesis and structural characterisation of aseries of complexes derived from L2. The preparation

Scheme 1. Reaction scheme for the synthesis of the series of cations trans-[C

and structure of the complex cis-[CoL2(NO2)2]+, whichcontains one N-bonded and one O-bonded nitrite ligandis also described.

2. Results and discussion

2.1. Synthesis

The synthesis of L2 was accomplished by the N-alkyl-ation of cyclam with 9-chloromethyl-anthracene followingthe method described by Fabrizzi et al. [7]. The syntheticroute to the series of complexes trans-[CoL2X2]+

(X ¼ Cl�, NCS� and NO2�) is summarised in Scheme 1.

The complex trans-[CoL2Cl2]+ was prepared by theaddition of cobalt(II) chloride to L2 in methanol. Subse-quent addition of hydrochloric acid and aerial oxidationled to formation of the trans-dichloro cobalt(III) complexwhich was isolated as its green chloride salt. The complextrans-[CoL2(NCS)2]+ was prepared by first adding cobal-t(II) perchlorate hexahydrate to L2 in methanol. The resul-tant complex (presumably with water as the axial ligands)was oxidised to cobalt(III) in air and then an excess ofsodium thiocyanate was added. The further addition ofexcess sodium perchlorate led to the isolation of the com-plex as its red/brown perchlorate salt. The complex trans-[CoL2(NO2)2]+ was prepared via in situ generation oftrans-[CoL2Cl2]+ followed by exchange of the chloride ionswith nitrite following the addition of an excess of sodiumnitrite. The complex was isolated as its orange perchloratesalt following the addition of NaClO4. The complexes werecharacterised by elemental analysis, 1H NMR, ESI-MS andsingle crystal X-ray diffraction. ESI-MS of each of the com-plexes discussed in this work clearly displayed M+ as themost abundant peak with [M�HX]+ and [M�2(HX)]+

peaks (X ¼ Cl�, NCS� and NO2�) also clearly distinguish-

able. The bridging methylene protons in these complexes

oL2X2]+ (X = Cl�, NCS� and NO2�) and the cis-[CoL2(NO2)2]+ cation.

S. Boyd et al. / Polyhedron 26 (2007) 1669–1676 1671

were inequivalent and appeared in each case as a single ABquartet [11], within the chemical shift range d 4.8–6.0 ppm.The presence of a single AB quartet was used to confirmthe isomeric purity of the complex.

We were also motivated to explore the synthesis oftrans-[CoL2(NO2)2]+ by reaction between L2 andNa3[Co(NO2)6] rather than by the method described above.In this case the macrocycle L2 was stirred withNa3Co(NO2)6 in a MeOH/H2O solution for 1 h. Followingwork up, a red-orange solid was obtained. The 1H NMRspectrum of this material was complex and different fromthat of trans-[CoL2(NO2)2]+. As indicated above, peaksin the 1H NMR spectrum arising from the bridging meth-ylene protons provide a guide to the isomeric purity ofcomplexes derived from L2. The presence in the 1HNMR spectrum of this product of three sets of AB quartets[11] indicated that a mixture of three isomers had resultedfrom the reaction of L2 with Na3[Co(NO2)6]. The spectrumcontained a set of doublets centred at d 5.2 ppm and theisomer associated with these peaks made up about 70%of the reaction product. Subsequent dissolution of thiscrude product in chloroform (as the nitrite salt) and slowrecrystallisation by diffusion of diethyl ether vapour per-mitted the isolation of the major product in pure form.ESI-MS and elemental analysis indicated the formationof [CoL2(NO2)2]NO2. Crystallographic analysis of the per-chlorate salt of this complex indicated formation of the cis-

Fig. 2. Crystal structure obtained for the trans-[CoL2Cl2]+ cation.Ellipsoids are represented at the 50% probability level.

Table 1Selected bond lengths (A) and angles (�) for all structure determinations

trans-[CoL2Cl2]+ trans-[CoL2(NCS

Co–N(1) 2.123(3) 2.067(5)Co–N(2) 1.973(3) 1.963(5)Co–N(3) 1.979(3) 1.983(5)Co–N(4) 1.978(3) 1.975(5)aCo–X(1) 2.247(1); Cl(1) 1.873(5); N(5)aCo–X(2) 2.271(1); Cl(2) 1.897(6); N(6)trans-Angles 173.95(5)–178.9(2) 176.0(2)–179.2(2)cis-Angles 85.5(1)–93.2(1) 86.6(2)–93.6(2)

a X(1), X(2) = atoms indicated.

isomer. The formation of the cis-isomer may reflect thekinetic inertness of the cobalt centre which was in a +3 oxi-dation state before inclusion in the macrocycle. Complexesof the trans-[CoL2X2]+ series were formed by reaction withcobalt in its more labile +2 oxidation state, thereby allow-ing the complex to rearrange to its perhaps more thermo-dynamically favourable trans configuration before beinglocked in by aerial oxidation to Co(III).

2.2. Crystal structures

According to Tobe the most thermodynamically favor-able configuration of a metal cyclam complex is one wherethe metal adopts a ‘‘trans(III)’’ configuration i.e. two pro-tons on adjacent amines, separated by a C3 link, pointupwards while the other two amine protons are directeddownwards [12]. This arrangement is favoured due to arelief of strain in the macrocyclic ring. Accordingly it is rea-sonable to expect that the complexes, [CoL2Cl2]+,[CoL2(NCS)2]+ and [CoL2(NO2)2]+ would adopt such aconfiguration.

The structure of the trans-[CoL2Cl2]+ complex is pre-sented in Fig. 2. The metal centre adopts an octahedralgeometry with the two trans chloro ligands Cl(1) andCl(2) at distances of 2.25(1) and 2.27(1) A, respectively,from the cobalt centre. The Cl(1)–Co–Cl(2) bond angle is173.95(5)�. The macrocycle adopts Tobe’s trans-(III) con-figuration. All Co–N bond lengths are typical for cobal-t(III)-cyclam complexes (ca. 1.97 A, Table 1). The N(1)–Co bond is an exception, a longer bond length of2.123(3) A perhaps a consequence of the relative steric bulkof the tertiary amino group [13]. All other C–N and non-aromatic C–C bond lengths are typical, as are all bondangles and torsional angles based on a staggered arrange-ment of the macrocycle about the metal. The relative orien-tations of the chromophore and macrocycle are presentedin Fig. 3a and b. The dihedral angle between the meanplanes of the anthracene and the four coordinating nitro-gen atoms is 29.75(6)� and the metal is separated by5.78 A from the centroid of the anthracene moiety. A slightbuckling is observed at one end of the anthracene whichmay be a result of steric interactions between the chromo-phore and cyclam ring. Apart from minor distortions asso-ciated with this buckling all other C–C bond lengths and

)2]+ trans-[CoL2(NO2)2]+ cis-[CoL2(NO2)2]+

2.10(1) 2.115(2)1.980(8) 2.011(2)1.957(9) 1.978(2)2.012(9) 2.007(2)1.93(1); N(5) 1.915(2); O(7)1.94(1); O(3) 1.936(2); N(5)171.5(5)–178.8(4) 173.2(1)–178.8(1)83.8(4)–96.7(5) 84.8(1)–95.2(1)

Fig. 3. A view of the trans-[CoL2Cl2]+ cation (a) normal to theapproximate plane of the macrocycle, (b) parallel to the approximateplane of the macrocycle.

Fig. 4. Crystal structure obtained for the trans-[CoL2(NCS)2]+ cation.Ellipsoids represented at the 50% probability level.

1672 S. Boyd et al. / Polyhedron 26 (2007) 1669–1676

angles are typical for anthracene. While the solid statestructure is not necessarily representative of the conforma-tion of the complex in solution, the aforementioned stericinteractions with the cyclam may significantly restrict therotation of the chromophore about the N(1)–C(11) andC(11)–C(12) bonds.

The structure of the thiocyanato complex is presented inFig. 4 and reveals both axial ligands to be N-bound like thearrangement in the trans-[Co(cyc)(NCS)2]+ complex inwhich the anthracene moiety is absent [14]. The cobalt cen-tre is octahedral with the two nitrogen atoms of the thiocy-anato ligands lying at distances of 1.873(5) and 1.897(6) Afrom the metal centre (Table 1). The other Co–N bondlengths are in the typical range expected for cobalt(III)-cyclam complexes (ca. 1.97 A, Table 1) with the exceptionof the Co–N(1) bond (2.067(5) A) reflecting the relative ste-ric bulk of the tertiary amino group [13]. A bend isobserved at atom N(5) (Co–N(5)–C(26) = 162.8(5)�). As

with the dichloro analogue of the complex, a trans-(III)configuration is adopted with the appended chromophoresituated well away from the macrocycle. The complexadopts a different conformation to that of the trans-[CoL2Cl2]+ complex in which the anthracene moiety istilted towards a five-membered chelate ring formed bythe metal, two amines and a 2-C link of the macrocycle(Fig. 3a). In the trans-[CoL2(NCS)2]+ complex, the anthra-cene is tilted towards a six-membered chelate ring. Thedihedral angle between the mean planes of the anthraceneand the four coordinating nitrogen atoms is 10.6(2)�, andthere is a 5.75 A separation between the cobalt centreand the centroid of the anthracene group. All C–C andC–N bond lengths and bond angles of the macrocycle areunexceptional. Observed torsion angles are as expectedbased on a staggered arrangement of the macrocycle aboutthe metal centre. Buckling at both ends of the chromo-phore occurs, which is likely to be a consequence of stericinteractions involving the anthracene and cyclam ring.Apart from minor distortions associated with thisbuckling, all anthracene C–C bond lengths and angles arenormal. Like the trans-[CoL2Cl2]+ complex, the above-mentioned steric interactions with the cyclam ring are likelyto restrict the rotation of the chromophore both in theplane and perpendicular to the plane of the macrocycle.

The structure of the trans-[CoL2(NO2)2]+ complex isdisplayed in Fig. 5 and reveals, quite remarkably, thatone of the nitrite ligands is O-bound and the other is N-bound. The metal adopts an octahedral geometry, withthe nitro and nitrito donor atoms at distances of1.93(1) A and 1.94(1) A, respectively, from the metalcentre. All other Co–N bond lengths are typical for cobal-t(III)-cyclam complexes (ca. 1.97 A, Table 1), the Co–N(1)and Co–N(4) bonds slightly elongated at 2.10(1) and2.012(9) A, respectively. All bond lengths, bond anglesand torsion angles in the macrocycle are as expected. TheN-bound nitro ligand appears to be stabilised by a hydro-gen bonding interaction between one of its oxygens and anamine hydrogen of the macrocycle with an O(2)� � �H–N(2)

Fig. 5. Crystal structure obtained for the trans-[CoL2(NO2)2]+ cation.Ellipsoids represented at the 50% probability level.

S. Boyd et al. / Polyhedron 26 (2007) 1669–1676 1673

separation of 2.72(1) A. Like the trans-[CoL2Cl2]+ com-plex, the anthracene is situated over a five-membered che-late ring of the macrocycle. The dihedral angle betweenthe mean planes of the anthracene and the four coordinat-ing nitrogen atoms is 26.9(2)� and the metal is separated by5.73 A from the centroid of the anthracene moiety. Likethe trans-[CoL2(NCS)2]+ complex, a buckling is observedat both ends of the chromophore. Apart from minor distor-tions associated with this buckling, all C–C bond lengthsand angles are as expected for anthracene.

The structure of the cis-[CoL2(NO2)2]+ complex isrepresented in Fig. 6. The macrocycle wraps itself aroundthe metal centre leaving the two monodentate ligands ina cis configuration. This is a remarkable arrangement fora cyclic quadridentate ligand and to the best of ourknowledge, the first reported involving cyclam in a cis-arrangement about a cobalt centre with two monoden-tate ligands. Two diagonally opposite amine hydrogenatoms are directed downwards from the plane of themacrocycle while the chromophore and the remainingamine hydrogen are directed upwards i.e. a cis-(V) con-

Fig. 6. Solid state structure of the cis-[CoL2(NO2)2]+ cation. Thermalellipsoids represented at the 50% probability level.

figuration according to Tobe’s classification [12]. Like theanalogous trans-[CoL2(NO2)2]+ complex, the structurereveals both a nitro and nitrito ligand in the one com-plex. The coordination geometry about the cobalt centreis octahedral, the nitro and nitrito donor atoms being atdistances of 1.936(2) and 1.915(2) A, respectively, fromthe metal centre. All other Co–N bond lengths areslightly longer when compared with the other complexesof the series (Table 1) with the exception of the Co–N(3)bond. All C–N and non-aromatic C–C bond lengths andbond angles are typical as are all torsion angles based ona staggered arrangement of the macrocycle about themetal centre. The structure reveals the anthracene to besituated well away from the macrocycle as one mayexpect given the steric crowding about the cobalt. Themean plane of the chromophore forms a dihedral angleof 13.95(5)� with the plane formed by nitrogen donoratoms N(1), N(2), N(3) and N(5). The cobalt is a sepa-rated by 5.86 A from the centroid of the anthracenegroup. Buckling is evident at one end of the chromo-phore, which is likely to be due to a steric interactionbetween the anthracene and cyclam ring. Like the com-plexes of the trans-[CoL2X2]+ series, these interactionsmay well restrict the rotation of the chromophore aboutboth the N(1)–C(11) and C(11)–C(12) bonds. Apart fromminor distortions associated with buckling of the chro-mophore, all aromatic C–C bond lengths and anglesare as expected for anthracene.

3. Conclusion

In this work we have demonstrated the coordinatingability of the ligand L2 by preparing a series of cobalt(III)complexes of the form [CoL2X2]+. In the ‘simple’ complextrans-[Co(cyc)(NO2)2]+ both nitro ligands are N-bound[15], so we were somewhat surprised to observe linkageisomerism in the solid state for both the cis- and trans-iso-mers of [CoL2(NO2)2]+. There are several examples ofmononuclear complexes containing both a nitro and nit-rito ligand in the one molecule for complexes of Ni(II)[16–19], Fe(III) [20], Ru(III) [21] and Cu(II) [22], althoughto our knowledge the complexes cis-[CoL2(NO2)2]+ andtrans-[CoL2(NO2)2]+ are the first examples reported forcobalt(III). The formation of the cis- rather than thetrans-isomer of [CoL2(NO2)2]+ appears to be determinedby the oxidation state of the cobalt salt used in the synthe-sis, with the kinetically inert cobalt(III) favouring theformation of the cis-isomer. The photochemistry of thesecobalt(III) complexes will be reported in more detailelsewhere [23], however it is worth noting here that thetwo isomers display marked differences in ground stateand excited state behaviour. The trans-isomer of [CoL2

(NO2)2]+ is labile to ligand exchange in the ground statewhile, in contrast, the cis-isomer is ground state inertbut undergoes ligand exchange reactions upon photoexci-tation making it a potentially useful photoactivated ligandrelease system.

1674 S. Boyd et al. / Polyhedron 26 (2007) 1669–1676

4. Experimental

4.1. Instrumentation

ESI-MS experiments were performed using an ion trap(Finnigan Mat) LC-Q spectrometer on dilute solutions ofthe complexes in methanol. 1H NMR spectra were mea-sured in d-chloroform, d3-acetonitrile and d4-methanol ona Unity Plus 400 spectrometer. Chemical shifts (d, positivedownfield) are given in ppm (solvent reference) and J val-ues in Hz. Aromatic hydrogens are labelled according toIUPAC conventions for anthracene (see supplementaryinformation). Absorption spectra were collected using aVarian Cary 50 Bio ultraviolet–visible spectrophotometerin methanol at 1.0 mM. Elemental analyses were per-formed by the Microanalytical Laboratory, Departmentof Chemistry, University of Otago, Dunedin, NewZealand.

4.2. Synthesis

Caution: perchlorate salts of metal complexes withorganic ligands are potentially explosive. No problems were

encountered with the complexes described below, however,

as a precaution, perchlorate salts should never be heated as

solids or be handled with metal spatulas.

Reactions were performed in air using as received solventsand AR reagents. Cyclam [24] and 9-chloromethyl-anthra-cene [25] were prepared by published procedures. 1-(Anthra-cen-9-ylmethyl)-1,4,8,11-tetraazacyclotetradecane (L2) wasprepared by the method described by Fabrizzi et al. [7].

4.3. trans-[CoL2Cl2]Cl trans-[1-(anthracen-9-ylmethyl)-

1,4,8,11-tetraazacyclotetradecane] dichloro cobalt(III)

chloride

A solution of cobalt(II) chloride hexahydrate (0.12 g,0.52 mmol) in MeOH (15 mL) was added to a solution ofL2 (0.20 g, 0.52 mmol) in MeOH (15 mL). Conc. HCl(1 mL) was added immediately to the brown solution andthe mixture was refluxed for 5 min. The solvent and acidwere then removed by passage of a stream of air acrossthe mixture. The residue was then stirred with MeOH(15 mL) to yield a green solution and some insoluble mate-rial. The mixture was filtered and the filtrate concentratedto 2 mL whereupon a green solid formed. This was col-lected and recrystallised by infusion of diethyl ether vapourinto a concentrated solution of the complex in MeOH toyield small olive green crystals (0.12 g, 0.22 mmol, 42%),m.p. 227–230 �C, ESI-MS data: M+ m/z 519, 521. Anal.Calc. for C25H34N4Cl3Co: C, 54.02; H, 6.17; N, 10.08,Cl, 19.13. Found: C, 53.84; H, 6.29; N, 9.78; Cl, 19.11%.Visible kmax: 618 nm, emax: 48 L mol�1 cm�1. 1H NMR(400 MHz, CDCl3): d 8.68 (d, J 8.8, 1H, Ar-8); 8.61 (br,1H, Ar-1); 8.53 (s, 1H, Ar-10); 8.35 (br, 1H, NH); 8.04(d, J 8.3, 2H, Ar-4,5); 7.44–7.63 (m, 4H, Ar-2,3,6,7); 5.96(br, 1H, NH); 5.93 (d, J 15.6, 1H, Ar-CH2-); 5.62 (d, J

15.6, 1H, Ar-CH2-); 4.0–1.0 (many complex multiplets,�20H, cyclam -CH2-).

4.4. trans-[CoL2(NCS)2]ClO4 Æ CH3CN trans-[1-

(anthracen-9-ylmethyl)-1,4,8,11-tetraazacyclotetradecane]

bis(thiocyanato-N) cobalt(III) perchlorate-CH3CN

A solution of cobalt(II) perchlorate hexahydrate (0.19 g,0.52 mmol) in MeOH (15 mL) was added to a solution ofL2 (0.20 g, 0.52 mmol) in MeOH (15 mL). Air was bubbledthrough the brown solution for 4 h and NaNCS (0.13 g,1.6 mmol) in MeOH (10 mL) was added. The intensely col-oured red-brown solution was refluxed for 1 h, then cooledand sodium perchlorate (0.36 g, 2.6 mmol) in H2O (2 mL)added. The solution was filtered and slowly concentratedto 2 mL by passing a gentle stream of air across the solu-tion whereupon a red-brown solid formed. The solid wascollected and recrystallised by the infusion of diethyl ethervapour into a concentrated solution of the complex in ace-tonitrile yielding intensely coloured red/brown plates(75 mg, 0.11 mmol, 22%), m.p. 205–207 �C, ESI-MSdata: M+m/z 565. Anal. Calc. for C27H34N6O4S2ClCo ÆCH3CN: C, 49.33; H, 5.28; N, 13.88; S, 9.08. Found: C,49.66; H, 5.33; N, 14.19; S, 9.13%. 1H NMR (400 MHz,CD3CN): d 8.68 (s, 1H, Ar-10); 8.30 (br, 2H, Ar-1,8);8.13 (d, J 8.4, 2H, Ar-4,5); 7.54–7.63 (m, 4H, Ar-2,3,6,7);6.37 (br, 1H, NH); 5.60 (br, 1H, NH); 5.23 (br, 1H,NH); 5.11 (d, J 15.6, 1H, Ar-CH2-); 4.89 (d, J 15.6,1H, Ar-CH2-); 3.8–1.0 (many complex multiplets, �20H,cyclam -CH2-).

4.5. trans-[CoL2(NO2)2]ClO4 trans-[1-(anthracen-9-

ylmethyl)-1,4,8,11-tetraazacyclotetradecane] (nitrite-N)

(nitrito-O) cobalt(III) perchlorate

A solution of cobalt(II) chloride hexahydrate (0.12 g,0.52 mmol) in MeOH (15 mL) was added to a solutionof L2 (0.20 g, 0.52 mmol) in MeOH (15 mL). Conc.HCl (1 mL) was added immediately to the brown solu-tion and the mixture was refluxed for 5 min. The solventand acid were then removed by passage of a stream ofair across the mixture. The residue was then stirred withMeOH (15 mL) to yield a green solution and some insol-uble material. The mixture was filtered and to the filtratewas added NaNO2 (0.11 g, 1.6 mmol) in H2O (2 mL).The resulting orange/red solution was heated at refluxfor 1 h, then cooled and sodium perchlorate (0.36 g,2.6 mmol) in H2O (2 mL) was added. The solution wasfiltered and slowly concentrated to 2 mL by passing astream of air across the solution whereupon an orangesolid formed. This was collected and recrystallised byinfusion of diethyl ether vapour into a concentrated solu-tion of the complex in acetonitrile to yield an orangemicrocrystalline solid (0.11 g, 0.18 mmol, 35%), m.p.125 �C (dec.), ESI-MS data: M+ m/z 541. Anal. Calc.for C25H34N6O8ClCo: C, 46.85; H, 5.35; N, 13.11; Cl,5.53. Found: C, 46.85; H, 5.50; N, 13.00; Cl, 5.23%.

S. Boyd et al. / Polyhedron 26 (2007) 1669–1676 1675

1H NMR (400 MHz, CD3CN): d 8.68 (s, 1H, Ar-10);8.21 (br, 2H, Ar-1,8); 8.12 (d, J 8.4, 2H, Ar-4,5); 7.53–7.63 (m, 4H, Ar-2,3,6,7); 6.43 (br, 1H, NH); 5.29 (br,1H, NH); 5.07 (d, J 15.1, 1H, Ar-CH2-); 4.88 (d, J

15.1, 1H, Ar-CH2-); 4.77 (br, 1H, NH); 4.0–1.0 (manycomplex multiplets, �20H, cyclam -CH2-).

4.6. cis-[CoL2(NO2)2]NO2 cis-[1-(anthracen-9-ylmethyl)-

1,4,8,11-tetraazacyclotetradecane] (nitrite-N)-(nitrito-O)-

cobalt(III) nitrite

A solution of trisodium hexanitrocobaltate(III) (0.33 g,0.57 mmol) in 80:20 MeOH:H2O (ca. 15 mL) was addedto a solution of L2 (0.20 g, 0.52 mmol) in MeOH (ca.15 mL) and the pale brown suspension which resultedwas stirred at room temperature for 1 h. The resultingblood red solution was filtered and the filtrate taken to dry-ness under a stream of N2. The residue was then stirredwith chloroform (ca. 15 mL) to yield a red solution andsome orange insoluble material (ca. 50 mg). The solidwas removed by filtration and the filtrate stirred with theslow addition of diethyl ether (ca. 100 mL) whereupon ared solid formed. This was collected and recrystallised byinfusion of diethyl ether vapour into a concentrated solu-tion of the complex in chloroform yielding irregularly-shaped ruby red crystals (54 mg, 0.092 mmol, 18%), m.p.175 �C (dec.), ESI-MS data: M+ m/z 541. Anal. Calc. forC25H34N7O6Co: C, 51.11; H, 5.83; N, 16.69. Found: C,51.28; H, 5.81; N, 16.61%. 1H NMR (400 MHz, CDCl3):d 8.98 (d, J 9.0, 1 H, Ar-8); 8.46 (s, 1H, Ar-10); 7.93 (m,

Table 2Crystallographic and data collection parameters for all structure determinatio

trans-[CoL2Cl2]+ trans-[Co

Anion Cl aClO4

Chemical formula C25H34Cl3CoN4 C29H37CFormula weight 555.84 706.16Crystal system orthorhombic monoclinSpace group Pbca (no. 61) P21/c (na (A) 9.824(2) 13.227(1b (A) 18.692(4) 11.042(1c (A) 27.006(2) 22.369(2a (�) 90 90b (�) 90 93.555(7c (�) 90 90Volume (A3) 4959.2(14) 3260.8(5Z 8 4Temperature (K) 293(2) 293(2)k, D(Mo Ka) (A) 0.71073 0.71073q(calc.) (g cm�3) 1.489 1.438F(000) 2320 1472l (cm�1) 1.037 0.782Crystal size (mm) 0.27 · 0.17 · 0.14 0.46 · 0.Reflections measured I > 2r(I) 4551 6660Incident reflections [Rint] 4351 [0.0194] 5774 [0.0wR2 (all data) 0.1015 0.1462R1(I > 2r(I)) 0.0462 0.0723Completeness of data to 2h (�) 1.000 to 50 0.998 to

a Includes one CH3CN solvent molecule.

3H, Ar-1,4,5); 7.65 (br, 1H, NH); 7.35–7.55 (m, 4H, Ar-2,3,6,7); 7.22 (br, 1H, NH); 6.54 (br, 1H, NH); 5.31 (d, J

15.4, 1H, Ar-CH2-); 5.13 (d, J 15.4, 1H, Ar-CH2-); 3.6–1.0 (many complex multiplets, �20H, cyclam -CH2-). The1H NMR spectrum was recorded with the addition oftwo drops of d6-DMSO to the CDCl3 solution to aid disso-lution of the compound.

4.7. Crystallography

The following is a short summary of the details of thecrystal used in each of the structure determinations includ-ing the methods employed in their structure determina-tions. Details of data collection and refinement aresummarised in Table 2. Full details, including all bondlengths, angles and atomic coordinates are recorded in ciffiles on the CCDC database. Structures were refined usinga full matrix least squares procedure based on F2 with alldata being used in the refinement. All structures weresolved and refined using SHELX-97 [26].

4.8. trans-[CoL2Cl2]Cl

Crystals suitable for X-ray crystallography were grownby slow evaporation from a dilute solution of the complexin methanol to produce green rectangular prisms. Datawere collected from a single crystal of approximate dimen-sions 0.27 · 0.17 · 0.14 mm on an Enraf-Nonius CAD4single crystal X-ray diffractometer using the x:2h scantechnique.

ns

L2(NCS)2]+ trans-[CoL2(NO2)2]+ cis-[CoL2(NO2)2]+

ClO4 ClO4

lCoN7O4S2 C25H34ClCoN6O8 C25H34ClCoN6O8

640.96 640.96ic orthorhombic orthorhombic

o. 14) Pbca (no. 61) Pna21 (no. 33)) 9.845(3) 14.0908(7)) 19.230(5) 21.765(1)) 29.328(8) 8.7994(4)

90 90) 90 90

90 90) 5553(3) 2698.6(2)

8 4293(2) 130(2)0.71073 0.710731.533 1.5782672 13360.774 0.797

19 · 0.04 0.25 · 0.12 · 0.10 0.17 · 0.17 · 0.4521983 16501

607] 3638 [0.3152] 6067 [0.0195]0.1723 0.08080.0758 0.0317

50 1.000 to 45 0.994 to 55

1676 S. Boyd et al. / Polyhedron 26 (2007) 1669–1676

4.9. trans-[CoL2(NCS)2]ClO4 Æ CH3CN

Crystals suitable for X-ray crystallography were grownby slow evaporation from a dilute solution of the complexin an acetonitrile/water mix to produce dark red/brownrectangular plates. Data were collected from a single crys-tal of approximate dimensions 0.46 · 0.19 · 0.04 mm on anEnraf-Nonius CAD4 single crystal X-ray diffractometerusing the x:2h scan technique.

4.10. trans-[CoL2(NO2)2]ClO4

Crystals suitable for X-ray crystallography were grownby H2O diffusion into a concentrated solution of the com-plex in acetonitrile to produce irregularly shaped orange/red crystals. Data were collected from a crystal of approx-imate dimensions 0.25 · 0.12 · 0.10 mm on a Bruker CCDarea detector, single crystal X-ray diffractometer. Inspec-tion of the diffraction pattern revealed that the crystalwas in fact a multiple crystal. A number of crystals wereinvestigated but all showed significant twinning. Usingthe program RLATT [27] it was possible to identify reflec-tions belonging to a single crystal. These reflections wereindexed in order to obtain a unit cell and an orientationmatrix. Since this crystal represented only a small portionof the multiple crystal, the data are very weak and thereare very few reflections at high angles. Given the paucityof data only the cobalt and chlorine atoms were refinedanisotropically. Despite the difficulties associated with thecrystal, the non-hydrogen atoms are clearly defined andthe connectivity is beyond doubt.

4.11. cis-[CoL2(NO2)2]ClO4

Crystals suitable for X-ray crystallography were grownfrom a solution of the perchlorate salt of cis-[CoL2-(NO2)2]NO2. This was prepared by dissolving cis-[CoL2-(NO2)2]NO2 (ca. 10 mg) in methanol (ca. 2 mL) and addingNaClO4 (ca. 5 equiv.) in water (0.5 mL) producing animmediate red precipitate. Crystals suitable for X-ray crys-tallography were grown by diethyl ether diffusion into adilute solution of the complex in acetonitrile to producerod-shaped ruby red crystals. Data were collected from acrystal of approximate dimensions 0.17 · 0.17 · 0.45 mmon a Bruker CCD area detector single crystal X-ray diffrac-tometer. The crystal was covered in oil and placed in astream of cooled nitrogen during the data collection.

Acknowledgement

We thank the Australian Research Council for financialsupport of this work.

Appendix A. Supplementary material

CCDC 617814, 617813, 617816 and 617815 containthe supplementary crystallographic data for trans-

[CoL2Cl2]+, trans-[CoL2(NCS)2]+, trans-[CoL2(NO2)2]+

and cis-[CoL2(NO2)2]+. These data can be obtained freeof charge via http://www.ccdc.cam.ac.uk/conts/retriev-ing.html, or from the Cambridge Crystallographic DataCentre, 12 Union Road, Cambridge CB2 1EZ, UK;fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.a-c.uk. Supplementary data associated with this articlecan be found, in the online version, at doi:10.1016/j.poly.2006.12.003.

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