Valeriya G. Makhankova

Novel polynuclear CuII/CoII complexes constructed from one and two Cu2Co triangles with antiferromagnetic exchange coupling

The reaction of acetonitrile solutions of CoX2·2H2O (X = NCS, I, Br) and 2-dimethylaminoethanol (HL) with copper powder in air leads to the formation of new tri- and hexa-nuclear complexes [Cu2Co(NCS)3L3]·½CH3CN (1), [Cu2Co(μ3-OH)I2L3]2·4CH3CN (2) and [Cu2Co(μ3-OH)Br2L3]2·2CH3CN (3). X-Ray crystallographic analysis of 1 reveals a symmetrical triangular core with one Co and two Cu atoms. The amino alkoxo- and SNCS-bridges between metal centres result in copper–copper and copper–cobalt separations of 3.413(2) and 3.103(2) A, respectively. Additional intermolecular association occurs through the NCS groups bridging Co and Cu centres of adjacent complex molecules to give chains. In the solid-state structures of 2 and 3 two symmetry-related Cu2Co units are linked by amino alkoxo bridges to form a hexanuclear molecule with intermetallic distances ranging from 3.102(2)–3.260(2) (Cu⋯Co) to 3.287(3)–3.931(2) A (Cu⋯Cu). The triangular planes formed by two copper and one cobalt atoms bridged by oxygen atoms from L groups are capped by a μ3-hydroxide not found in the core of 1. The hexanuclear units show no significant intermolecular contacts in the solid state. Variable-temperature magnetic susceptibility studies performed on 1 and 2 in the temperature range 5–280 K gave satisfactory fits to the observed susceptibility data by assuming isotropic magnetic exchange interactions and using the appropriate spin Hamiltonians considering 1 as a trinuclear entity and 2 as a combination of two trinuclear entities. An antiferromagnetic spin exchange operates in the Cu2Co units of both complexes [JCuCu = 40.1(4) (1), 48.7(9) (2); JCuCo = 141(2) (1), 86.2(1.3) cm−1 (2)] while a weak ferromagnetic coupling is active between Cu and Co ions from different trinuclear entities in 2 (JCuCo′ = −8.0(4) cm−1).

Homogeneous Cobalt/Vanadium Complexes as Precursors for Functionalized Mixed Oxides in Visible‐Light‐Driven Water Oxidation

The heterometallic complexes (NH4 )2 [Co(H2 O)6 ]2 [V10 O28 ]⋅4 H2 O (1) and (NH4 )2 [Co(H2 O)5 (β-HAla)]2 [V10 O28 ]⋅4 H2 O (2) have been synthesized and used for the preparation of mixed oxides as catalysts for water oxidation. Thermal decomposition of 1 and 2 at relatively low temperatures (<500 °C) leads to the formation of the solid mixed oxides CoV2 O6 /V2 O5 (3) and Co2 V2 O7 /V2 O5 (4). The complexes (1, 2) and heterogeneous materials (3, 4) act as catalysts for photoinduced water oxidation. A modification of the thermal decomposition procedure allowed the deposition of mixed metal oxides (MMO) on a mesoporous TiO2 film. The electrodes containing Co/V MMOs in TiO2 films were used for electrocatalytic water oxidation and showed good stability and sustained anodic currents of about 5 mA cm-2 at 1.72 V versus relative hydrogen electrode (RHE). This method of functionalizing TiO2 films with MMOs at relatively low temperatures (<500 °C) can be used to produce other oxides with different functionality for applications in, for example, artificial photosynthesis.

Spectroscopic and Magnetostructural Evidence for the Formation of [Cu0.5Co0.5(H2Tea)X] Mixed-Crystal Compounds from Zerovalent Cu and Co Salts in the Presence of Triethanolamine (H3Tea -Triethanolamine; X = SCN, Cl)

Mixed crystals [Cu0.5Co0.5(H2Tea)(SCN)] (1), [Cu0.5Co0.5(H2Tea)Cl] (2) (H3Tea = triethanolamine) have been obtained by the open-air reaction of metallic copper with cobalt(II) chloride/cobalt(II) thiocyanate and triethanolamine in non-aqueous solvents, like dmf, dmso, CH3OH and CH3CN. The simultaneous presence of copper and cobalt in the mixed crystals was unambiguously determined by atomic absorption, EPR and electronic spectroscopy. Details of 1 have been studied structurally, and a preliminary report of the structure of 2 is also given. The mononuclear species 1 and 2 contain crystallographically indistinguishable Cu(II) and Co(II) ions in virtually identical trigonal bipyramidal sites. The molecules are linked together by O-H···O hydrogen bonds to give chains. The values of the temperature independent μeff of 3.50 and 3.48 μB for 1 and 2 (in the range of T = 20 - 280 K), respectively, agree with the 1:1 molar ratio of the metals in both samples.

Chlorido­bis­(1,10-phenanthroline-κ2N,N′)copper(II) chlorido­(1,10-phen­anthroline-κ2N,N′)(pyridine-2,6-di­carboxyl­ato-κ3O2,N,O6)manganate(II) methanol monosolvate

The title complex, [CuCl(C12H8N2)2][Mn(C7H3NO4)Cl(C12H8N2)]·CH3OH, consists of discrete [CuCl(phen)2]+ cations (phen is 1,10-phenanthroline), [MnCl(pydc)(phen)]− anions (H2pydc is 2,6-pyridine-2,6-dicarboxylic acid) and one methanol solvent molecule of crystallization per asymmetric unit. It should be noted, that a solvent-masking procedure as implemented in OLEX2 [Dolomanov et al. (2009). J. Appl. Cryst. 42, 339–341 ▶] was used to remove the electronic contribution from one disordered solvent molecule, presumably methanol. Only the atoms used in the refined model are reported in chemical formula and related values. The CuII ion is five-coordinated by two phenanthroline ligands and one chloride ion in a distorted trigonal–bipyramidal geometry. The dihedral angle between the phen ligands is 65.21 (5)°. The MnII ion is six-coordinated by one Cl atom, two N atoms from a phen ligand, as well one N atom and two O atoms from pydc in a distorted octahedral coordination geometry, with cis angles ranging from 72.00 (8) to 122.07 (8)° and trans angles ranging from 143.98 (8) to 163.15 (6)°. In the crystal, C—H⋯O, O—H⋯O and C—H⋯Cl hydrogen bonds, cation–anion π–π interactions between the phen ring systems with centroid–centroid distances in the range 3.881 (34)–4.123 (36) Å, as well as cation–cation, anion–anion π–π interactions between the phen rings with centroid–centroid distances in the range 3.763 (4)–3.99 (5) Å and pydc rings with centroid–centroid distances 3.52 (5) Å link the various components.

Zerovalent copper in reactions with triethanolamine and cobalt(II) salts: syntheses, structural, spectroscopic and magnetic studies of novel mixed-metal Cu/Co complexes

triethanolamine and cobalt(II) salts: syntheses, structural, spectroscopic and magnetic studies of novel mixed-metal Cu/Co complexes. V.G. Makhankova, O.Yu. Vassilyeva, a V.N. Kokozay, B.W. Skelton , a Chemistry Dpt, National Taras Shevchenko University, Volodimirska st. 64, Kyiv 01033, Ukraine, b Chemistry Dpt, University of Western Australia, Nedlands, Western Australia 6907, Australia