Redox non-innocence of thioether crowns: spectroelectrochemistry and electronic structure of formal nickel(III) complexes of aza-thioether macrocycles.

The Ni(II) complexes [Ni([9]aneNS(2)-CH(3))(2)](2+) ([9]aneNS(2)-CH(3)=N-methyl-1-aza-4,7-dithiacyclononane), [Ni(bis[9]aneNS(2)-C(2)H(4))](2+) (bis[9]aneNS(2)-C(2)H(4)=1,2-bis-(1-aza-4,7-dithiacyclononylethane) and [Ni([9]aneS(3))(2)](2+) ([9]aneS(3)=1,4,7-trithiacyclononane) have been prepared and can be electrochemically and chemically oxidized to give the formal Ni(III) products, which have been characterized by X-ray crystallography, UV/Vis and multi-frequency EPR spectroscopy. The single-crystal X-ray structure of [Ni(III)([9]aneNS(2)-CH(3))(2)](ClO(4))(6)·(H(5)O(2))(3) reveals an octahedral co-ordination at the Ni centre, while the crystal structure of [Ni(III)(bis[9]aneNS(2)-C(2)H(4))](ClO(4))(6)·(H(3)O)(3)·3H(2)O exhibits a more distorted co-ordination. In the homoleptic analogue, [Ni(III)([9]aneS(3))(2)](ClO(4))(3), structurally characterized at 30 K, the Ni-S distances [2.249(6), 2.251(5) and 2.437(2) Å] are consistent with a Jahn-Teller distorted octahedral stereochemistry. [Ni([9]aneNS(2)-CH(3))(2)](PF(6))(2) shows a one-electron oxidation process in MeCN (0.2 M NBu(4)PF(6), 293 K) at E(½)=+1.10 V versus Fc(+)/Fc assigned to a formal Ni(III)/Ni(II) couple. [Ni(bis[9]aneNS(2)-C(2)H(4))](PF(6))(2) exhibits a one-electron oxidation process at E(½)=+0.98 V and a reduction process at E(½)=-1.25 V assigned to Ni(II)/Ni(III) and Ni(II)/Ni(I) couples, respectively. The multi-frequency X-, L-, S-, K-band EPR spectra of the 3+ cations and their 86.2% (61)Ni-enriched analogues were simulated. Treatment of the spin Hamiltonian parameters by perturbation theory reveals that the SOMO has 50.6%, 42.8% and 37.2% Ni character in [Ni([9]aneNS(2)-CH(3))(2)](3+), [Ni(bis[9]aneNS(2)-C(2)H(4))](3+) and [Ni([9]aneS(3))(2)](3+), respectively, consistent with DFT calculations, and reflecting delocalisation of charge onto the S-thioether centres. EPR spectra for [(61)Ni([9]aneS(3))(2)](3+) are consistent with a dynamic Jahn-Teller distortion in this compound.

Magnetic behavior of odd- and even-electron metal carbonyl clusters: the case study of [Co(8)Pt(4)C(2)(CO)(24)](n-) (n = 1, 2) carbide cluster.

The reaction of [Co(6)C(CO)(15)](2-) with 2 equiv of PtCl(2)(Et(2)S)(2) affords the new heterobimetallic [Co(8)Pt(4)C(2)(CO)(24)](2-), [1](2-), carbonyl cluster. [1](2-) undergoes reversible chemical and electrochemical oxidation and reduction processes disclosing a complete series of [1](n-) (n = 1-4) clusters. The mono- and dianion of [1](n-) have been isolated as their tetra-substituted ammonium salts and fully characterized by means of IR, (13)C NMR, ESI-MS, and X-ray crystallography. Variable-temperature (VT) solid-state EPR studies on pure crystalline samples indicate that both [1](2-) and [1](-*) are paramagnetic, due to a doublet state of the latter and a triplet state of [1](2-). This conclusion is supported by SQUID measurements on the same crystalline sample of [1](2-). The present study indisputably demonstrates that even-electron transition metal carbonyl clusters (TMCC) can be magnetic.

Tripodal thiols as ligands for molecular magnets: very strong antiferromagnetic exchange interactions in vanadium(III) clusters.

The synthesis, structural and magnetic characterisation of [V(III)(3)O(tmme)(2)(diimine)(2)Cl] [diimine=2,2'-bipyridine (1) or 1,10-phenanthroline (2)] and (HNEt(3))(2)[V(III)(4)O(tmme)(4)] (3) is reported, in which H(3)tmme is tris(mercaptomethyl)ethane, MeC(CH(2)SH)(3), the thiol analogue of the famous tripodal alcohol ligands typified by H(3)thme [tris(hydroxymethyl)ethane, MeC(CH(2)OH)(3)]. Complexes 1 and 3 have "T-shaped" and square topologies, respectively, and the latter is centred on a rare example of a square-planar oxide. The tri-thiolate ligands bind the periphery of the clusters and provide such strong antiferromagnetic exchange pathways that in both cases only a single total spin state is occupied up to room temperature, in the absence of metal-metal bonding. Magnetic data, electronic structure calculations and electrochemical data are reported.

Ferromagnetic Ni(II) discs.

A family of planar disc-like hexa-, octa- and decametallic Ni(II) complexes exhibit dominant ferromagnetic exchange. The deca- and octametallic clusters [Ni(II) (10)(tmp)(2)(N(3))(8)(acac)(6)(MeOH)(6)] (1, H(3)tmp=1,1,1-tris(hydroxymethyl)propane; acac=acetylacetonate) and [Ni(II) (8)(thme)(2)(O(2)CPh)(4)(Cl)(6)(MeCN)(6)(H(2)O)(2)] (2, H(3)thme=1,1,1-tris(hydroxymethyl)ethane) represent rare examples of Ni(II)-based single-molecule magnets, and [Ni(II) (10)] (1) possesses the largest barrier to magnetisation reversal of any Ni(II) single-molecule magnet to date.

Electronic structure of the mononuclear Ag(ii) complex [Ag([18]aneS(4)O(2))](2+) ([18]aneS(4)O(2) = 1,10-dioxa-4,7,13,16-tetrathiacyclooctadecane).

The structure of [Ag([18]aneS(4)O(2))](PF(6))(2).CH(2)Cl(2) shows a highly unusual and unexpected boat conformation for the macrocycle with square-planar S(4)-coordination at the formal Ag(ii) centre and the two ether O-centres lying on the same side of the S(4) plane; the SOMO in [Ag([18]aneS(4)O(2))](2+) possesses 22.7% Ag 4d(xy) character, as determined by multi-frequency EPR spectroscopy and supported by DFT calculations.

Crystallographic, electrochemical, and electronic structure studies of the mononuclear complexes of Au(I)/(II)/(III) with [9]aneS2O ([9]aneS2O = 1-oxa-4,7-dithiacyclononane).

The mononuclear macrocyclic complexes [Au(I)([9]aneS2O)2]BF4 x MeCN 1a, [Au(II)([9]aneS2O)2](BF4)2 x 2 MeCN 2a, and [Au(III)([9]aneS2O)2](ClO4)6(H5O2)(H3O)2 3 ([9]aneS2O = 1-oxa-4,7-dithiacyclononane) have been prepared and structurally characterized by single crystal X-ray crystallography. The oxidation of [Au([9]aneS2O)2](+) to [Au([9]aneS2O)2](2+) involves a significant reorganization of the co-ordination sphere from a distorted tetrahedral geometry in [Au([9]aneS2O)2](+) [Au-S 2.3363(12), 2.3877(12), 2.6630(11), 2.7597(13) A] to a distorted square-planar co-ordination geometry in [Au([9]aneS2O)2](2+). The O-donors in [Au([9]aneS2O)2](2+) occupy the axial positions about the Au(II) center [Au...O = 2.718(2) A] with the S-donors occupying the equatorial plane [Au-S 2.428(8) and 2.484(8) A]. [Au([9]aneS2O)2](3+) shows a co-ordination sphere similar to that of [Au([9]aneS2O)2](2+) but with significantly shorter axial Au...O interactions [2.688(2) A] and equatorial Au-S bond lengths [2.340(4) and 2.355(6) A]. The cyclic voltammogram of 1 in MeCN (0.2 M NBu4PF6, 253 K) at a scan rate of 100 mV s(-1) shows an oxidation process at E(p)(a) = +0.74 V and a reduction process at E(p)(c) = +0.41 V versus Fc(+)/Fc assigned to the two-electron Au(III/I) couple and a second reduction process at E(p)(c) = +0.19 V assigned to the Au(I/0) couple. This electrochemical assignment is confirmed by coulometric and UV-vis spectroelectrochemical measurements. Multifrequency EPR studies of the mononuclear Au(II) complex [Au([9]aneS2O)2](2+) in a fluid solution at X-band and as frozen solutions at L-, S-, X-, K-, and Q-band reveal g(iso) = 2.0182 and A(iso) = -44 x 10(-4) cm(-1); g(xx) = 2.010, g(yy) = 2.006, g(zz) = 2.037; A(xx) = -47 x 10(-4) cm(-1), A(yy) = -47 x 10(-4) cm(-1), A(zz) = -47 x 10(-4) cm(-1); P(xx) = -18 x 10(-4) cm(-1), P(yy) = -10 x 10(-4) cm(-1), and P(zz) = 28 x 10(-4) cm(-1). DFT calculations predict a singly occupied molecular orbital (SOMO) with 27.2% Au 5d(xy) character, consistent with the upper limit derived from the uncertainties in the (197)Au hyperfine parameters. Comparison with [Au([9]aneS3)2](2+) reveals that the nuclear quadrupole parameters, P(ii) (i = x, y, z) are very sensitive to the nature of the Au(II) co-ordination sphere in these macrocyclic complexes. The observed geometries and bond lengths for the cations [Au([9]aneS2O)2](+/2+/3+) reflect the preferred stereochemistries of d(10), d(9), and d(8) metal ions, respectively, with the higher oxidation state centers being generated at higher anodic potentials compared to the related complexes [Au([9]aneS3)2](+/2+/3+).

Incorporation of fused tetrathiafulvalenes (TTFs) into polythiophene architectures: varying the electroactive dominance of the TTF species in hybrid systems.

A novel polythienylenevinylene (PTV) and two new polythiophenes (PTs), featuring fused tetrathiafulvalene (TTF) units, have been prepared and characterized by ultraviolet-visible (UV-vis) and electron paramagnetic resonance (EPR) spectroelectrochemistry. All polymers undergo two sequential, reversible oxidation processes in solution. Structures in which the TTF species is directly linked to the polymer backbone (2 and 4) display redox behavior which is dictated by the fulvalene system. Once the TTF is spatially removed from the polymer chain by a nonconjugated link (polymer 3), the electroactivity of both TTF and polythiophene moieties can be detected. Computational studies confirm the delocalization of charge over both electroactive centers (TTF and PT) and the existence of a triplet dication intermediate. PTV 4 has a low band gap (1.44 eV), is soluble in common organic solvents, and is stable under ambient conditions. Organic solar cells of polymer 4:[6,6]-phenyl-C(61) butyric acid methyl ester (PCBM) have been fabricated. Under illumination, a photovoltaic effect is observed with a power conversion efficiency of 0.13% under AM1.5 solar simulated light. The onset of photocurrent at 850 nm is consistent with the onset of the pi-pi absorption band of the polymer. Remarkably, UV-vis spectroelectrochemistry of polymer 4 reveals that the conjugated polymer chain remains unchanged during the oxidation of the polymer.

Heteropolymetallic copper(II)-gold(III) dithiocarbamate [2]catenanes via magic ring synthesis.

A rare class of mixed-metal [2]catenane has been assembled via magic ring synthesis of dinuclear copper(II) and gold(III) dithiocarbamate macrocycles.

The effect of mechanistic pathway on activity in the Pd and Pt catalysed methoxycarbonylation of ethene.

All the intermediates involved in the platinum catalysed methoxycarbonylation of ethene have been characterised by in situ NMR; the low activity of platinum catalysts in this reaction is shown to be due to trapping of the active intermediates by carbon monoxide at every step in the catalytic cycle and to the ready reversibility of the product forming reactions.

An in situ electrochemical cell for Q- and W-band EPR spectroscopy.

A simple design for an in situ, three-electrode spectroelectrochemical cell is reported that can be used in commercial Q- and W-band (ca. 34 and 94 GHz, respectively) electron paramagnetic resonance (EPR) spectrometers, using standard sample tubing (1.0 and 0.5 mm inner diameter, respectively) and within variable temperature cryostat systems. The use of the cell is demonstrated by the in situ generation of organic free radicals (quinones and diimines) in fluid and frozen media, transition metal ion radical anions, and on the enzyme nitric oxide synthase reductase domain (NOSrd), in which a pair of flavin radicals are generated.

Co(II), Ni(II), Cu(II) and Zn(II) complexes of tetraphenylazadipyrromethene.

The synthesis, crystallographic and spectroscopic properties of four divalent isomorphous metal complexes of tetraphenylazadipyrromethene are described.

New hybrid semiconductor materials based on viologen salts of bimetallic Fe-Pt and Fe-Au carbonyl clusters: first structural characterization of the diradical pi-dimer of the diethylviologen monocation and EPR evidence of its triplet state.

The synthesis, structure, spectroscopic characterization and electrical resistivity of the [EtV](2)[Fe(4)Pt(CO)(16)], [EtV][Fe(3)Pt(3)(CO)(15)].THF, [EtV][Fe(4)Au(CO)(16)](2)2.THF (EtV=1,1'-diethyl-4,4'-bipyridilium cation) and [NEt(4)](2)[Fe(4)Au(CO)(16)] is reported. The crystal structure of [EtV](2)[Fe(4)Pt(CO)(16)] is based on infinite stacks of [(EtV)(*+)](2) pi-dimers rotated by 90 degrees and isolated [Fe(4)Pt(CO)(16)](2-) ions. Within each pi-dimer, the [EtV](*+) radical ions are perfectly eclipsed and the distance between their mean planes is 3.275 A. The EPR spectrum of the solid material at room temperature clearly indicates the presence of a significantly populated triplet state of the pi-dimer, by showing signals both at Deltam=1 and Deltam=2. The solid-state structure of [EtV][Fe(3)Pt(3)(CO)(15)].THF is based on the ionic packing of [EtV](2+) and [Fe(3)Pt(3)(CO)(15)](2-) ions, inferred from a comparison of their molecular parameters with literature data. Significant electron transfer could have been expected to give [EtV](*+)[Fe(3)Pt(3)(CO)(15)](*-) on the basis of their formal redox potentials. In spite of their different stoichiometries, the structures of [EtV][Fe(4)Au(CO)(16)](2).2 THF and [NEt(4)](2)[Fe(4)Au(CO)(16)] both contain an isomer of the monoanion [Fe(4)Au(CO)(16)](-) in solution (previously characterized in the solid state as a [NMe(3)CH(2)Ph](2)[Fe(4)Au(CO)(16)]Cl mixed salt). Resistivity measurements on pellets of powdered samples of the above compounds indicate that their tetrasubstituted ammonium salts, and complex [EtV][Fe(4)Au(CO)(16)](2)2.THF, largely behave as insulators. However, the [EtV](2)[Fe(4)Pt(CO)(16)] and [EtV][Fe(3)Pt(3)(CO)(15)].THF samples respectively display resistivities 3 and 4 orders of magnitude less than those of their corresponding ammonium salts and could be classified as semiconductor materials.

Synthesis, structural, and magnetic studies on a redox family of tetrametallic vanadium clusters: {VIV4}, {VIII2VIV2}, and {VIII4} butterfly complexes.

The synthesis, crystal structures, and magnetic properties are reported for a redox family of butterfly-type tetrametallic vanadium alkoxide clusters, namely [V2(VO)2(acac)4(RC{CH2O}3)2] (R=Me 1, Et 2, CH2OH 3), [V2(VO)2(acac)2(O2CPh)2(MeC{CH2O}3)2] (5), [(VO)4(MeOH)2(O2CPh)2({HOCH2}C{CH2O}3)2] (6), [V4Cl2(dbm)4(RC{CH2OH}3)2] (R=Me 7, Et 8, CH2OH 9), and [V4Cl2(dbm)4(MeO)6] (10). The cluster cores are {VIV4} (6), {VIII2VIV2} (1-5), and {VIII4} (7-10), with examples of both isomeric forms of the of the mixed-valence cores (either VIII or VIV ions forming the butterfly body). Magnetic studies reveal the clusters to be dominated by antiferromagnetic exchange interactions in each case. The magnetic exchange parameters are determined for representative examples of each core type. {VIV4} and {VIII4} have diamagnetic ground states. The two isomeric {VIII2VIV2} types are found to give rise to either an S=0 ground state with a number of low-lying excited states due to competing antiferromagnetic exchange interactions (VIII2 butterfly body) or to a well-isolated S=1 ground state (VIV2 butterfly body).

Studies of a linear single-molecule magnet.

Reaction of the dinuclear complex [Mn2O2(bpy)4](ClO4)3 with H3cht (cis,cis-l,3,5-cyclohexanetriol) in MeCN produces the complex [Mn3(Hcht)2(bpy)4](ClO4)3.Et2O.2MeCN (1.Et2O.2MeCN). Dc magnetic susceptibility measurements reveal the existence of weak ferromagnetic exchange between the three Mn ions, leading to a spin ground state of S = 7, with D = -0.23 cm(-1). W-Band (94 GHz) EPR measurements on restrained powdered crystalline samples confirm the S = 7 ground state and determine the ground state zero-field splitting (ZFS) parameters of D = -0.14 cm(-1) and B4(0)= +1.5 x 10(-5) cm(-1). The apparent 4th order behaviour is due to a breakdown of the strong exchange limit approximation (J approximately d, the single-ion ZFS). Single crystal dc relaxation decay and hysteresis loop measurements reveal the molecule to have an appreciable energy barrier to magnetization relaxation, displaying low temperature sweep rate and temperature-dependent hysteresis loops. Density functional studies confirm the ferromagnetic exchange coupling between the Mn ions.

Four copper(II) pyrazolido complexes derived from reactions of 3{5}-substituted pyrazoles with CuF(2) or Cu(OH)(2).

Treatment of CuF(2) with 2 equiv of 3{5}-[pyrid-2-yl]pyrazole (Hpz(Py)), 3{5}-phenylpyrazole (Hpz(Ph)) or 3{5}-[4-fluorophenyl]pyrazole (Hpz(PhF)) in MeOH, followed by evaporation to dryness and recrystallisation of the solid residues, allows solvated crystals of [{Cu(micro-pz(Py))(pz(Py))}(2)] (1), [{Cu(micro-pz(Ph))(2)}(4)] (2) and [Cu(4)F(2)(micro(4)-F)(micro-pz(PhF))(5)(Hpz(PhF))(4)] (3) to be isolated in moderate-to-good yields. Similar reactions of these three pyrazoles with Cu(OH)(2) in refluxing MeOH respectively afford 1, 2 and [Cu(pz(PhF))(2)(Hpz(PhF))(2)] (4) in ca. 10% yield. Crystalline 1 x 1/2H(2)O x 2CHCl(3) contains two independent dinuclear molecules with a puckered di-(1,2-pyrazolido) bridge motif, linked by a bridging, hydrogen-bonding water molecule. Compound 2 x 1/2C(5)H(12), containing cyclic, square tetranuclear complex molecules, is the first homoleptic divalent metal pyrazolide to have a discrete molecular rather than polymeric structure, for a metal other than Pd or Pt. The two independent complex molecules in 3 x 3/4CH(2)Cl(2) x Hpz(PhF) contain a unique tetrahedral [Cu(4)(micro(4)-F)](7+) core, three of whose edges are spanned by bridging pyrazolido groups. Magnetic data show that the copper centres in 1 and 3 are antiferromagnetically coupled, but that dried bulk samples of 2 do not retain their molecular structure.

Design and synthesis of binucleating macrocyclic clefts derived from Schiff-base calixpyrroles.

The syntheses, characterisation and complexation reactions of a series of binucleating Schiff-base calixpyrrole macrocycles are described. The acid-templated [2+2] condensations between meso-disubstituted diformyldipyrromethanes and o-phenylenediamines generate the Schiff-base pyrrolic macrocycles H(4)L(1) to H(4)L(6) upon basic workup. The single-crystal X-ray structures of both H(4)L(3).2 EtOH and H(4)L(6).H2O confirm that [2+2] cyclisation has occurred, with either EtOH or H2O hydrogen-bonded within the macrocyclic cleft. A series of complexation reactions generate the dipalladium [Pd2(L)] (L=L(1) to L(5)), dinickel [Ni2(L(1))] and dicopper [Cu2(L)] (L=L(1) to L(3)) complexes. All of these complexes have been structurally characterised in the solid state and are found to adopt wedged structures that are enforced by the rigidity of the aryl backbone to give a cleft reminiscent of the structures of Pacman porphyrins. The binuclear nickel complexes [Ni2(mu-OMe)2Cl2(HOMe)2(H(4)L(1))] and [Ni2(mu-OH)2Cl2(HOMe)(H(4)L(5))] have also been prepared, although in these cases the solid-state structures show that the macrocyclic ligand remains protonated at the pyrrolic nitrogen atoms, and the Ni(II) cations are therefore co-ordinated by the imine nitrogen atoms only to give an open conformation for the complex. The dicopper complex [Cu2(L(3))] was crystallised in the presence of pyridine to form the adduct [Cu2(py)(L(3))], in which, in the solid state, the pyridine ligand is bound within the binuclear molecular cleft. Reaction between H(4)L(1) and [Mn(thf){N(SiMe(3))2}2] results in clean formation of the dimanganese complex [Mn2(L(1))], which, upon crystallisation, formed the mixed-valent complex [Mn2(mu-OH)(L(1))] in which the hydroxo ligand bridges the metal centres within the molecular cleft.

Redox non-innocence of thioether macrocycles: elucidation of the electronic structures of mononuclear complexes of gold(II) and silver(II).

The mononuclear +2 oxidation state metal complexes [Au([9]aneS(3))(2)](2+) and [Ag([18]aneS(6))](2+) have been synthesized and characterized crystallographically. The crystal structure of the Au(II) species [Au([9]aneS(3))(2)](BF(4))(2) shows a Jahn-Teller tetragonally distorted geometry with Au-S(1) = 2.839(5), Au-S(2) = 2.462(5), and Au-S(3) = 2.452(5) A. The related Ag(II) complex [Ag([18]aneS(6))](ClO(4))(2) has been structurally characterized at both 150 and 30 K and is the first structurally characterized complex of Ag(II) with homoleptic thioether S-coordination. The single-crystal X-ray structure of [Ag([18]aneS(6))](ClO(4))(2) confirms octahedral homoleptic S(6)-thioether coordination. At 150 K, the structure contains two independent Ag(II)-S distances of 2.569(7) and 2.720(6) A. At 30 K, the structure retains two independent Ag(II)-S distances of 2.615(6) and 2.620(6) A, with the complex cation retaining 3-fold symmetry. The electronic structures of [Au([9]aneS(3))(2)](2+) and [Ag([18]aneS(6))](2+) have been probed in depth using multifrequency EPR spectroscopy coupled with DFT calculations. For [Au([9]aneS(3))(2)](2+), the spectra are complex due to large quadrupole coupling to (197)Au. Simulation of the multifrequency spectra gives the principal g values, hyperfine (A) and quadrupole (P) couplings, and furthermore reveals non-co-incidence of the principal axes of the P tensor with respect to the A and g matrices. These results are rationalized in terms of the electronic and geometric structure and reveal that the SOMO has ca. 30% Au 5d(xy)() character, consistent with DFT calculations (27% Au character). For [Ag([18]aneS(6))](2+), detailed EPR spectroscopic analysis confirms that the SOMO has ca. 26% Ag 4d(xy)() character and DFT calculations are consistent with this result (22% Ag character).

Copper(II) complexes of thioether-substituted salcyen and salcyan derivatives and their silver(I) adducts.

New syntheses are reported of 5-tert-butyl-2-hydroxy-3-methylsulfanylbenzaldehyde, 5-tert-butyl-2-hydroxy-3-phenylsulfanyl-benzaldehyde, and salcyen (H(2)L(1)-H(2)L(3)) and salcyan (H(2)L(4)-H(2)L(6))-type ligands derived from these aldehydes and from 5-tert-butyl-2-hydroxybenzaldehyde. The complexes [CuL](L(2-)=[L(1)](2-)-[L(6)](2-)) bearing sulfanyl substituents each show two distinct voltammetric ligand-based oxidations under the same conditions, the first of which is chemically reversible. The first oxidation product is much longer lived by coulometry for the salcyen than for the salcyan ligand complexes, despite the latter having a substantially lower oxidation potential. The lifetimes of all the ligand oxidation products in this system are substantially smaller than for similar compounds derived from 3,5-di(tert-butyl)-2-hydroxybenzaldehyde (Dalton Trans., 2004, 2662). Attempted chemical oxidation of the Schiff base compounds using AgBF(4) yielded instead stable silver(i) adducts. A crystal structure of one such compound showed that the Ag atom was coordinated in a slightly bent geometry by the two ligand sulfanyl groups, with two additional long-range Ag...O interactions to the phenoxide donors. EPR spectra showed that some of these silver adducts dimerise in CH(2)Cl(2), probably through basal, apical intermolecular Cu-O...Cu bridging. In contrast the parent copper(ii) complexes are all monomeric in this solvent by EPR.

Cascade complexation: a single cyano bridge links a pair of Cu(II) cations.

A series of structurally characterised mu-cyanodicopper(II) cryptates shows moderately strong antiferromagnetic interaction in the range -2J= 150-200 cm(-1), at the high end of the observed range for such assemblies. The lowest magnetic exchange coupling parameter is displayed where there is slight bending of the M-CN-M assembly, enforced by the constraints of cryptate encapsulation. Thermally accessible triplet EPR spectra are observed with zero-field splittings of the order of 0.13-0.14 cm(-1), confirming collinear ground-state dz2 orbitals for Cu(II), consistent with their trigonal-bipyramidal coordination geometries.