M. Tamilselvan

Abstract: The title complex, [CoCl(C5H13N)(C2H8N2)2]Cl2·H2O, comprises one chloridobis(ethyl­enediamine)(n-pentyl­amine)cobalt(III) cation, two chloride counter-anions and a water mol­ecule. The CoIII atom of the complex is hexa­coordinated by five N and one Cl atoms. The five N atoms are from two chelating ethyl­enediamine and one n-pentyl­amine ligands. Neighbouring cations and anions are connected by N—H⋯Cl and N—H⋯O hydrogen bonds to each other and also to the water mol­ecule.

Abstract: In the title compound, [CoCl(C2H8N2)2(C7H9N)]Cl2·0.5H2O, there are two crystallographically independent cations and anions and one water mol­ecule in the asymmetric unit. Both CoIII ions are bonded to two chelating ethylenediamine ligands, one benzylamine molecule and one chloride ion. The crystal packing is through N—H⋯O, N—H⋯Cl and O—H⋯Cl inter­actions.

Abstract: Structurally integrated cobalt(III) complexes showing interesting surface affinity in the interfacial electron transfer reactions were synthesized by incorporating alkyl amines into the coordination sphere of cis-[CoIII(en)2(RNH2)Cl]Cl2; (where RNH2 = MeNH2 (1), EtNH2 (2), PrnNH2 (3), BunNH2 (4), BuiNH2 (5), PennNH2 (6), HexnNH2 (7) and BzNH2 (8)) through a modified synthetic route. Such complexes are playing important role as electron acceptors in the interfacial electron transfer reactions taking place between metal complex and nanosized semiconductor particles in energy conversion schemes. The complexes were characterized by spectral, 1H NMR and 13C NMR techniques, which indicate the 1,2-diamino ethane site angles are closely similar forming five membered gauche configuration. Single crystal X-ray refinements were made to explore the structures of five complexes (2)–(5) and (7). The complexes under study crystallize either in monoclinic or orthorhombic structure and the space consists; (2) P21/n, (3) P212121, (4) Pbca, (5) P21 and (7) P21/n. The Co(III) ion does not have an electronic preference, however, the structures reflect the conformational preference of RNH2 ligand.

Abstract: Interfacial electron transfer reaction mechanism has been probed using λ = 254 nm excited TiO 2 nanoparticles and cis -[Co III (en) 2 (RNH 2 )Cl]Cl 2 adsorbates (where RNH 2 = MeNH 2 , EtNH 2 , Pr n NH 2, Bu n NH 2, Bu i NH 2, Pen n NH 2 , Hex n NH 2 , Bz n NH 2 ) in aqueous 2-propanol. These tailor made complexes differing in coordination environment due to RNH 2 adhere onto TiO 2 surface producing compact nano-TiO 2 //cobalt(III)–(RNH 2 ) surface compound. The surface of the anatase under UV irradiation is uniquely powerful as adsorbent due to inherent hydrophobic/hydrophilic properties. Therefore, the compact structure facilitates an efficient electron transfer to the Co(III) center resulting a high photoefficiency of formation of Co(II). A model for the electron transfer is arrived by considering: (i) the overlap of conduction band of TiO 2 with the acceptor level (Co center): (e − , CB)/(e − , tr) + (Co III , ad) → Co II and (ii) electronic coupling of donor level (localized on Ti center) with acceptor level (Co center): Ti (center) + (Co III , ad) → Co II . These pathways indicate accumulation of electron and appropriately available for reduction of the adhered complex ion. Significant insights were gained on the role of RNH 2 moiety in modifying compact structure of TiO 2 –cobalt(III)–RNH 2 compound, redox power of semiconductor surface, and the proposed mechanism of interfacial electron transfer reactions.

Abstract: In the title compound, [CoCl(C2H8N2)2(C7H9N)]Cl2·H2O, the CoIII ion has a distorted octa­hedral coordination environment and is surrounded by four N atoms in an equatorial plane, with the other N and Cl atoms occupying the axial positions. The crystal packing is stabilized by N—H⋯O, N—H⋯Cl and O—H⋯Cl inter­actions.

Abstract: In the title compound, [CoCl(CH5N)(C3H10N2)2]Cl2·H2O, the CoIII ion has an octa­hedral coordination environment and is surrounded by four N atoms of two propane-1,3-diamine ligands in the equatorial plane, with another N atom of the methylamine ligand and a Cl atom occupying the axial positions. The crystal packing is stabilized by inter­molecular N—H⋯O, N—H⋯Cl, and O—H⋯Cl inter­actions, generating a three-dimensional network.