CuII CuI Research Articles

Synthesis, characterization, crystal structure, and theoretical studies of a mixed-ligand copper(I) iodide complex of an asymmetric Schiff base ligand 2-((pyridin-4-yl)methelenamino)-3-aminomaleonitrile and triphenylphosphine co-ligand

Single pot synthesis of a new mixed-ligand iodide bridged dimeric Cu(I) complex, [L2CuI2(μ-I)2(PPh3)2](1) has been carried out by combining copper(I)iodide, an asymmetric Schiff base ligand 2-((pyridin-4-yl)methelenamino)-3-aminomaleonitrile (L) and a co-ligand triphenylphosphine (PPh3). L and 1 have been characterized by 1H NMR, IR and EIMS spectrometry, elemental analysis and DFT studies. The crystal structure of 1 has been determined by single-crystal X-ray analysis and it has been found that it is a dimer with —{CuI—(m-I2)—CuI}— rhomboid core with the bridged iodide ion. 1 crystallized as 1·CH2Cl2. At room temperature in dichloromethane the ligand L is non-emissive whereas the complex 1 is photoluminescent. The E1/2 value of the CuI—CuII couple of 1 in dichloromethane is 0.46 V (vs. Ag/AgCl in 1 M KCl, scan rate 100 mV/s). The Hirshfeld surface analysis of the complex 1·CH2Cl2 showed H⋯H, N⋯H and I⋯H interactions of 52.3 %, 13.1 % and 7.4 %, respectively, which revealed that the main intermolecular interactions were H⋯H intermolecular interactions.

New copper complexes with N-(5,6-dihydro-4H-1,3-thiazin-2-yl)benzamide ligand

Crystals of two copper complexes with N-(5,6-dihydro-4H- +1,3-thiazin-2-yl)benzamide were obtained and characterized by X-ray diffraction analysis. LETDI studies have shown that the composition of the complex is inhomogeneous, and the precipitated crystals can have different structures being of Cuii or Cui–Cuii types. The complexes are significantly more cytotoxic toward the leukemic Jurkat cell line than to healthy lymphocytes.

Five-coordinate [(L2)2CuII(X)]z+ (X = H2O, z = 2; X = N3−, SCN−, NO2−, MeCO2−, Cl−, Br−, z = 1; L2 = 1-benzyl-[3-(2-pyridyl)]pyrazole) complexes: Structural index, EPR and redox potential correlations

Mononuclear five-coordinate complexes [(L2)2CuII(X)]z+(ClO4)n (X = H2O 1, n = z = 2; X = N3−2, SCN−3, NO2−4, MeCO2−5, Cl−6, Br−7, n = z = 1; L2 = 1-benzyl-[3-(2-pyridyl)]pyrazole) have been synthesized and structurally characterized with crystal composition 1, 2, 3·2MeCN, 4·Et2O, 5·3H2O, 6·MeCN and 7·MeCN. The bidentate ligand L2 provides a pyridyl and a pyrazole for coordination. Structural index parameter (τ; it assumes a value of 0 and 1 for ideal square pyramidal and trigonal bipyramidal geometry, respectively) for 1–3, 5–7 are 0.60, 0.01, 0.33, 0.26, 0.62, 0.57, respectively. Absorption and EPR spectroscopic, and redox (except for 1) properties of 1–7 have been investigated. Cathodic peak potential (Epc, V vs. saturated calomel electrode, SCE) values in MeCN of 2–7 are −0.05, 0.07, 0.05, 0.05, 0.23 and 0.14, respectively. For anion-bound complexes 2, 3, 5–7 useful correlations have been established: (i) Epc (CuII–CuI redox process) vs. structural index parameter τ, (ii) g‖vs. τ, (iii) A‖vs. τ and (iv) Epcvs. g‖. The observed trends have been rationalized.

Direct Determination of Electron-Transfer Properties of Dicopper-Bound Reduced Dioxygen Species by a Cryo-Spectroelectrochemical Approach.

Direct experimental determination of redox properties of superoxo (O2.- ) and peroxo (O22- ) embedded in dicopper complexes bearing an unsymmetrical binucleating ligand was achieved using cryo-electrochemistry and cryo-spectroelectrochemistry in dichloromethane. Cyclic voltammetry for dicopper(I) (1+ ) oxidation to a CuI CuII mixed-valent species (12+ ) under inert atmosphere at 193 K reveals slow heterogeneous electron-transfer kinetics, indicative of a large reorganization energy. Oxygenation of the dicuprous complex 1+ gives the bridged peroxo dicopper(II) species 3+ , which is reversibly oxidized to the superoxo complex 22+ at E0 =0.11 V (vs. SCE) with a small inner sphere electron-transfer reorganization energy, λi =0.54 eV, determined from variable temperature electrochemical impedance spectroscopy. The data suggest that the O2.- /O22- redox process occurs directly on the O2 -derived core.

Copper(I) oxalate complexes: Synthesis, structures and surprises

A series of dinuclear copper(I) oxalate complexes was synthesized by the direct acid-base reaction of Cu2O with oxalic acid in ethanol with a ligand, or in neat ligand. The complexes incorporated a variety of ligands L (L=triphenylphosphine, 1,2-bis(diphenylphosphino)ethane, triphenylphosphite, diisopropyl sulfide, cyclooctadiene and cyclohexylisocyanide) and had the general formula LnCu(μ2-C2O4)CuLn (n=1 or 2). The CuI/CuII mixed-valence trinuclear compound (iPr2S)2CuI(C2O4)CuII(C2O4)CuI(iPr2S)2 was formed concomitantly with the target dinuclear Cu2C2O4(iPr2S)4 complex, shedding light on the mechanism of disproportionation of this family of complexes. With norbornadiene (nbd) as a ligand, however, a coordination polymer Cu2C2O4(nbd) was formed. Also, the same reaction with L=2,9-dimethyl-1,10-phenanthroline or pyridine resulted in the known tetrahedral complex ions [CuLm]+ (m=2 or 4). Lastly, the ligand di-2-(1-di-(2-picolyl)amino)propyl disulfide produced not the expected Cu(I) oxalate complex, but a Cu(II) picolylamine oxalate coordination polymer. All products were structurally characterized by single-crystal X-ray diffraction if soluble, and by powder X-ray diffraction methods if not.

Ni(II)/Cu(I) based coordination polymers with heterofunctional ligands integrating pyridine and pyrimidinethione structural motifs

Two coordination polymers with the heterofunctional ligand 4-PPT (4-(pyridin-4-yl)pyrimidine-2-thiol), {[Ni(4-PPT)2]·2(DMF)}n (1) and {[Cu2(4-PPT)2]·2(DMF)}n (2), have been isolated by reaction with Ni(OAc)2 and CuBr2, respectively. 1 shows a two-dimensional (2-D) layered structure with a 4-connected sql topology wherein the 4-PPT ligand exhibits a uniform μ2-1, κS κN(pyrimidine): 2, κN(pyridine) bridging mode. 2 also features an sql net based on a unique CuI4S4 cluster in which the 4-PPT ligand adopts two kinds of coordination modes, viz. μ3-1, κN(pyrimidine): 2,3, κS and μ4-1, κN(pyrimidine): 2,3, κS: 4, κN(pyridine). For comparison, the reaction of CuBr2 with 3-PPT (4-(pyridin-3-yl)pyrimidine-2-thiol, an isomer of 4-PPT) under the same conditions was also examined, which yielded a 2-D Cu(I)-based coordination polymer with the 63-hcb topology, [CuBr(3-ppds)]n (3) (3-ppds=di(4-(pyridin-3-yl)pyrimidin-2-yl)disulfide). In 3,3-ppds was in situ generated from 3-PPTvia an S–S oxidative coupling reaction, concurrent with in situ reduction CuII–CuI. UV–Vis diffuse reflectance and luminescence spectra have been measured for 1 and 2 in order to compare their photophysical properties.

Synthesis, Crystal Structure, and Electroconducting Properties of a 1D Mixed-Valence Cu(I)–Cu(II) Coordination Polymer with a Dicyclohexyl Dithiocarbamate Ligand

A new mixed-valence Cu(I)–Cu(II) 1D coordination polymer, [CuI4CuIIBr4(Cy2dtc)2]n, with an infinite chain structure is synthesized by the reaction of Cu(Cy2dtc)2 (Cy2dtc− = dicyclohexyl dithiocarbamate, C13H22NS2) with CuBr·S(CH3)2. The as-synthesized polymer consists of mononuclear copper(II) units of CuII(Cy2dtc)2 and tetranuclear copper(I) cluster units, CuI4Br4. In the cluster unit, all the CuI ions have distorted trigonal pyramidal coordination geometries, and the CuI–CuI or CuI–CuII distances between the nearest copper ions are shorter than the sum of van der Waals radii for Cu–Cu.

Protonation of a biologically relevant Cu(II) μ-thiolate complex: ligand dissociation or formation of a protonated Cu(I) disulfide species?

The proton-induced electron-transfer reaction of a Cu(II) μ-thiolate complex to a Cu(I) -containing species has been investigated, both experimentally and computationally. The Cu(II) μ-thiolate complex [Cu(II) 2 (L(Me) S)2 ](2+) is isolated with the new pyridyl-containing ligand L(Me) SSL(Me) , which can form both Cu(II) thiolate and Cu(I) disulfide complexes, depending on the solvent. Both the Cu(II) and the Cu(I) complexes show reactivity upon addition of protons. The multivalent tetranuclear complex [Cu(I) 2 Cu(II) 2 (LS)2 (CH3 CN)6 ](4+) crystallizes after addition of two equivalents of strong acid to a solution containing the μ-thiolate complex [Cu(II) 2 (LS)2 ](2+) and is further analyzed in solution. This study shows that, upon addition of protons to the Cu(II) thiolate compound, the ligand dissociates from the copper centers, in contrast to an earlier report describing redox isomerization to a Cu(I) disulfide species that is protonated at the pyridyl moieties. Computational studies of the protonated Cu(II) μ-thiolate and Cu(I) disulfide species with LSSL show that already upon addition of two equivalents of protons, ligand dissociation forming [Cu(I) (CH3 CN)4 ](+) and protonated ligand is energetically favored over conversion to a protonated Cu(I) disulfide complex.

Thermodynamics of the Cu(II) μ-thiolate and Cu(I) disulfide equilibrium: a combined experimental and theoretical study.

The redox equilibrium between dinuclear Cu(II) μ-thiolate and Cu(I) disulfide structures has been analyzed experimentally and via DFT calculations. Two new ligands, L(2)SSL(2) and L(4)SSL(4), and their Cu(II) μ-thiolate and Cu(I) disulfide complexes were synthesized. For L(2)SSL(2), these two redox-isomeric copper species are shown to be in equilibrium, which depends on both temperature and solvent. For L(4)SSL(4) the μ-thiolate species forms as the kinetic product and further evolves into the disulfide complex under thermodynamic control, which creates the unprecedented possibility to compare both species under the same reaction conditions. The energies of the μ-thiolate and disulfide complexes for two series of related ligands have been calculated with DFT; the results rationalize the experimentally observed structures, and emphasize the important role that steric requirements play in the formation of the Cu(II) thiolate structure.

Dinuclear CuII–CuII and CuI–CuII Complexes of a Compartmental Ligand – Syntheses, Structures, Magnetic, and Catalytic Studies

AbstractDinuclear CuII–CuII (1) and CuI–CuII (2) complexes were derived from a new N4O2 donor compartmental ligand (H2L) by changing the nature of the Cu precursors used. Single‐crystal X‐ray diffraction studies revealed that the Cu1 site in 1 has octahedral geometry and is in the inner compartment of the ligand axially coordinated by two ClO4– anions, whereas the outer Cu2 ion has square‐pyramidal geometry. In 2, there are two copper dinuclear complexes (A and B) in the asymmetric unit; the inner core is occupied by Cu1/Cu3 in the +2 oxidation state in a square‐planar geometry. The Cu2/Cu4 ion occupies the outer sites and has distorted tetrahedral geometry with a +1 oxidation state. Complexes 1 and 2 were obtained simply by changing Cu(ClO4)2 in 1 to Cu(ClO4)2 and Cu(bipy)(NO3)2 in 2; the bipyridyl (bipy) ligand induces the reduction of CuII to CuI, which is trapped in the CuI–CuII dinuclear product. The oxidation states of the metal ions were ascertained from charge‐balance considerations as well as from bond valence sum (BVS) calculations. No signature of intervalence charge transfer (IVCT) was observed by spectroscopy (UV/Vis/NIR) as well as from the low‐temperature magnetic studies. This might be because of the presence of two copper centers in two different geometries with a wide separation between them (ca. 3.27 Å). For 1, the best fit of the χT vs. T data to the dimer model gives J/kB = –262(1) K and gav = 2.05(5), which indicates that there is a strong antiferromagnetic coupling between the two Cu atoms. In 2, the CuI center is diamagnetic and, thus, the remaining S = 1/2 CuII magnetic center follows a Curie law with g = 2.06(5). Under homogeneous conditions, both complexes showed catalytic epoxidation of cyclooctene, styrene, and norbornene to the corresponding epoxides with high selectivities and turnover numbers (TONs), which seem to be slightly better than the reported values for CuII Schiff base complexes.

Halido‐Bridged 1D Mixed‐Valence CuI–CuII Coordination Polymers Bearing a Piperidine‐1‐carbodithioato Ligand: Crystal Structure, Magnetic and Conductive Properties, and Application in Dye‐Sensitized Solar Cells

AbstractNew mixed‐valence CuI–CuII 1D coordination polymers of the structure [CuI2CuIIX2(Pip‐dtc)2(CH3CN)2]n [Pip‐dtc = piperidine‐1‐carbodithioate; X = Br (1a), I (1b)] containing a dithiocarbamate derivative have been synthesized and structurally characterized by X‐ray diffraction. The 1D infinite chains were formed from mononuclear copper units [Cu(Pip‐dtc)2] connected by bromido‐ or iodido‐bridged copper dinuclear units that include acetonitrile ligands {i.e., [Cu2X2(CH3CN)2]}. Evaluation of the magnetic properties of 1a and 1b revealed that these complexes displayed relatively strong antiferromagnetic interactions [J = –20.4 cm–1 (1a) and J = –18.8 cm–1 (1b)] between unpaired electrons of the copper(II) ions through the dinuclear halido–copper(I) units. Impedance spectroscopy revealed that complexes 1a and 1b exhibit intriguing semiconducting properties at activation energies of Ea = 0.78 eV (1a) and Ea = 0.62 eV (1b). Coordination polymers 1a and 1b were then adopted as the sensitizing material in dye‐sensitized solar cells (DSSCs).

A novel mixed valent CuII–CuI 2D framework made of a hydrazone and μ-SCN bridged metallacyclic loops cross-linked by μ3-SCN chains

A mixed valent copper complex [Cu(II)Cu(I)(L)(μ-SCN)(μ(3)-SCN)](n) (LH = N'-((pyridin-2-yl)methylene)acetohydrazide) has been synthesized and characterized. It is a unique example of a 2D mixed valent Cu(II)-Cu(I) interlinked molecular assembly with a very unusual bridging property of the hydrazone ligand. An extraordinary in situ partial Cu(II)→ Cu(I) reduction is observed in this system at room temperature.

2-Benzoylpyridine thiosemicarbazone as a novel reagent for the single pot synthesis of dinuclear CuI–CuII complexes: formation of stable copper(ii)–iodide bonds

2-Benzoylpyridine thiosemicarbazone {R(1)R(2)C(2)=N(2)·N(3)H-C(1)(=S)-N(4)H(2), R(1) = py-N(1), R(2) = Ph; Hbpytsc} with copper(I) iodide in acetonitrile-dichloromethane mixture has formed stable Cu(II)-I bonds in a dark green Cu(II) iodo-bridged dimer, [Cu(2)(II)(μ-I)(2)(η(3)-N(1),N(2),S-bpytsc)(2)] 1. Copper(I) bromide also formed similar Cu(II)-Br bonds in a dark green Cu(II) bromo-bridged dimer, [Cu(2)(II)(μ-Br)(2)(η(3)-N(1),N(2),S-bpytsc)(2)] 3. The formation of dimers 1 and 3 appears to be due to a proton coupled electron transfer (PCET) process wherein copper(I) loses an electron to form copper(II), and this is accompanied by a loss of -N(3)H proton of Hbpytsc ligand resulting in the formation of anionic bpytsc(-). When copper(I) iodide was reacted with triphenylphosphine (PPh(3)) in acetonitrile followed by the addition of 2-benzoylpyridine thiosemicarbazone in dichloromethane (Cu : PPh(3) : Hbpytsc in the molar ratio 1:1:1), both Cu(II) dimer 1 and an orange Cu(I) sulfur-bridged dimer, [Cu(2)(I)I(2)(μ-S-Hbpytsc)(2)(PPh(3))(2)] 2 were formed. Copper(I) bromide with PPh(3) and Hbpytsc also formed Cu(II) dimer 3 and an orange Cu(I) sulfur-bridged dimer, [Cu(2)(I)Br(2)(μ-S-Hbpytsc)(2)(PPh(3))(2)] 4. While complexes 2 and 4 exist as sulfur-bridged Cu(I) dimers, 1 and 3 are halogen-bridged. The central Cu(2)S(2) cores of 2 and 4 as well as Cu(2)X(2) of 1 (X = I) and 3 (X = Br) are parallelograms. One set of Cu(II)-I and Cu(II)-Br bonds are short, while the second set is very long {1, Cu-I, 2.565(1), 3.313(1) Å; 3, Cu-Br, 2.391(1), 3.111(1) Å}. The Cu···Cu separations are long in all four complexes {1, 4.126(1); 2, 3.857(1); 3, 3.227(1); 4, 3.285(1) Å}, more than twice the van der Waals radius of a Cu atom, 2.80 Å. The pyridyl group appears to be necessary for stabilizing the Cu(II)-I bond, as this group can accept π-electrons from the metal.

Valence-induced assembly of CuI–CuII ions into different discrete coordination architectures by a disk-shaped polypyridyl ligand

The valences of metal ions were found to play key roles in controlling the formation and structures of discrete coordination architectures in a copper and disk-shaped hexa-monodentate ligand system. When Cu(I) and Cu(II) ions react with a polydentate ligand HPDQ, a hexanuclear "double-decker" like discrete "LM(3)M(3)L" coordination architecture (CuI)(6)(HPDQ)(2)(CHCl(3))(8) (complex 1), and a "LM(3)L + LM(3)" composite structure complex (Cu(NO(3))(2))(6)(HPDQ)(3) (complex 2) are formed, respectively.

A catalytic process for the selective oxidation of alcohols by copper (II) complexes

Abstract Novel copper (II)–N–(2-pyridyl)–N'–(5-R-salicylidene) hydrazine triphenylphosphine complexes have been synthesized and characterized. The complexes were effective in the catalytic oxidation of primary and secondary alcohols in presence of periodic acid (H5IO6) as oxidant. The oxidation reactions were carried out in acetonitrile. Electrochemical electron transfer study reveals CuII–CuI reduction in methanolic solutions. A mechanistic study of the above reactions has been proposed.

Electrochemically-driven conformational shift in mono- and di-copper constrained macrotricyclic cyclen receptors

An electrochemical study of mono- and di-copper constrained cyclen macrotricycles is presented. Electrochemical data in DMF solution indicate that the reduction of dinuclear complexes occurs in two steps in the -0.4 to -0.8 V vs.AgCl/Ag potential range yielding CuII CuI and CuI CuI species further reduced to Cu metal at highly negative potentials. Mononuclear complexes are reduced in two steps to CuI and Cu metal. Electrochemical data suggest that reduction of both mononuclear and dinuclear complexes approach a square scheme involving electrochemically-driven conformational shifts for metal ions. The presence of endo- and exo-forms of the complexes are revealed by changes in the electrochemical response of the complexes in the presence of tetraethylammonium chloride, 1-azabicyclo[2.2.2]octane and diazabicyclo[2.2.2]octane competing ligands.

Copper complexes with ferrocenyl pendants: Evidence for an FeII ∼ CuII ⇌ FeIII ∼ CuI electron transfer equilibrium leading to a reaction with dioxygen

Three new nitrogen-donor ligands with ferrocenyl pendants, namely ferrocenylmethylbis(2-pyridylethyl)amine (L1), ferrocenylmethylbis(2-pyridylmethyl)amine (L2), and 1-ferrocenylmethyl-4,7-diisopropyl-1,4,7-triazacyclononane (L3), have been synthesised. Copper(II) complexes of these ligands have been made and their physicochemical and redox properties characterised. Crystal structures of [Cu(L2)X2·0.5Et2O (X = Cl, Br), [Cu(L2)(OTf)2(CH3OH)], [Cu(L3)Cl2], and [{(L3)Cu}2(μ-OH)2](OTf)2·0.5Et2O are reported. Oxidation of each complex with ceric ion affords the corresponding FeIII ∼ CuII species. Variations in ligand design, the choice of co-ligand (chloride, bromide, trifluoromethanesulfonate (OTf) or solvent) and the choice of solvent allowed, in the case of acetonitrile solutions of [Cu(L1)(H2O)2](OTf)2, the close matching of the FeIII–FeII and CuII–CuI electrochemical couples. [Cu(L1)(H2O)2](OTf)2 reacts with dioxygen in acetonitrile, but is stable in other solvents such as tetrahydrofuran. Electronic spectra of the complex in acetonitrile exhibit a prominent ferrocenium ion band. These results are interpreted in terms of an intramolecular electron transfer equilibrium between FeII ∼ CuII and FeIII ∼ CuI tautomers for the complex that leads to it reacting with dioxygen; their possible biological relevance is discussed.

Synthesis, crystal structure and properties of trigonal bipyramidal [M(L5)2(H2O)]·H2O complexes [M = cobalt(II) (S = 3/2) or copper(II) (S = 1/2); HL5 = N-(2-chloro-6-methylphenyl)pyridine-2-carboxamide

Using a bidentate ligand N-(2-chloro-6-methylphenyl)pyridine-2-carboxamide (HL5), in its deprotonated form, two new five-co-ordinate complexes of composition [M(L5)2(H2O)]·H2O (M = CoII 1 or CuII 2) have been prepared and characterized including X-ray crystallography. The co-ordination geometry at CoII and CuII is approximately trigonal bipyramidal (two deprotonated amide nitrogens and a water molecule in the equatorial plane and two pyridines in the axial positions), being more distorted in the case of CuII. The observed distortion is caused by (i) a small bite angle of the chelating ligand and (ii) the presence of two ortho substituents, a chloro and a methyl group, on the phenyl ring (steric effect). To the best of our knowledge, 1 represents the first structurally characterized mononuclear high-spin cobalt(II) complex with a pyridine amide ligand. The magnetic moments of 1 and 2 at 300 K reveal that the compounds are paramagnetic (1 has S = 3/2 and 2 has S = 1/2), both as solids and in dmf solution. Temperature dependent magnetic susceptibility measurements confirmed their spin state. The stereochemistry of the cobalt(II) centre in 1 does not change to any measureable extent on dissolution in dmf (cf. solid and solution state absorption spectra). The geometry of the copper(II) centre in 2 observed in the solid state is not retained in dmf solution (absorption spectra), changing to a tetragonal stereochemistry. Cyclic voltammetric measurements (dmf solution; glassy carbon electrode) on 1 reveal an oxidative response at 0.48 V vs. saturated calomel electrode (SCE) and a reductive response at –1.66 V corresponding to CoIII–CoII and CoII–CoI redox couples, respectively. For 2 the CuII–CuI process was observed at –0.53 V vs. SCE.

Synthesis, magnetism, 1H NMR and redox activity of dicopper(II) complexes having a discrete {Cu2(μ-phenoxide)2}2+ unit supported by a non-macrocyclic ligand environment. Crystal structure of [Cu2(L)2(OClO3)2] [HL = 4-methyl-2,6-bis(pyrazol-1-ylmethyl)phenol] †

Reaction between 4-methyl-2,6-bis(pyrazol-1-ylmethyl)phenol (HL) or its 3,5-dimethylpyrazole derivative (HL′) and Cu(ClO4)2·6H2O afforded [CuII2(L/L′)2(OClO3)2] 1 and 2. Complex 1 has been structurally characterized showing that each copper(II) centre is square pyramidal with two bridging phenoxide oxygens and two terminal pyrazole nitrogens in the equatorial plane and a perchlorate oxygen atom axially co-ordinated. Variable-temperature magnetic susceptibility measurements revealed that the dicopper(II) centres are strongly antiferromagnetically coupled [singlet–triplet energy separation, 2J (in cm–1): –1204 for 1 and –798 for 2]. The complexes exhibit 1H NMR spectra within δ 0–10 due to their S = 0 ground state. In MeCN solution they exhibit ligand field transitions in the range 14 300–16 600 cm–1 and phenolate-to-copper(II) charge-transfer transition at ≈22 700 cm–1. In MeCN solution each complex displays three consecutive irreversible responses (scan rate of 50 mV s–1) with Epc values (V vs. SCE) at –0.02, –0.54 and –0.86 (1) and 0.00, –0.42 and –0.80 (2). The first two responses are due to CuII–CuI and the most cathodic response to CuI–Cu0 redox processes, respectively.

Synthesis, spectroscopic, photophysical and electrochemical properties of cyano-bridged copper(I)–ruthenium(II) complexes

Complexes of the formula [(N–N)Cu(AsPh3)CN] (N–N=2,2′–bipyridine, 1,10–phenanthroline) have been synthesized. Ru(bpy)2Cl2.2H2O and [(η5–cp)Ru(PPh3)2Cl] react with [(N–N)Cu(AsPh3)CN] to give cyano-bridged compounds. IR spectral studies in the low frequency region (700–50 cm−1) and 4000–400 cm−1 region reveal cyano bridging in the complexes. Luminescence measurements suggest oxidation of metal centres (CuI–CuII and RuII–RuIII) on excitation at a charge transfer band. This has been substantiated with electrochemical studies of complexes which exhibit quasi-reversible reductions viz. RuIII⧹RuII and CuII⧹CuI. The deposition of metallic copper is also observed at a potential of −1.55 V. Based on these data, a mechanism for photo-redox reaction of complexes has been presented. The properties of these bimetallic complexes are compared with those of parent complexes.