Heterobi-, tri- and tetra-metallic cyanide-bridged complexes based on pentacarbonylcyanochromate(0) and penta-, cis-tetra- and fac-tri-ammineruthenium(III) groups: optical metal-metal charge transfer and electrochemical characteristics

Metal-metal charge transfer and solvatochromism in cyanomanganese carbonyl complexes of ruthenium and osmium

The complexes [(H3N)5Ru(II)(mu-NC)Mn(I)Lx]2+, prepared from [Ru(OH2)(NH3)5]2+ and [Mn(CN)L(x)] {L(x) = trans-(CO)2{P(OPh)3}(dppm); cis-(CO)2(PR3)(dppm), R = OEt or OPh; (PR3)(NO)(eta-C5H4Me), R = Ph or OPh}, undergo two sequential one-electron oxidations, the first at the ruthenium centre to give [(H3N)5Ru(III)(mu-NC)Mn(I)Lx]3+; the osmium(III) analogues [(H3N)5Os(III)(mu-NC)Mn(I)Lx]3+ were prepared directly from [Os(NH3)5(O3SCF3)]2+ and [Mn(CN)Lx]. Cyclic voltammetry and electronic spectroscopy show that the strong solvatochromism of the trications depends on the hydrogen-bond accepting properties of the solvent. Extensive hydrogen bonding is also observed in the crystal structures of [(H3N)5Ru(III)(mu-NC)Mn(I)(PPh3)(NO)(eta-C5H4Me)][PF6]3.2Me2CO.1.5Et2O, [(H3N)5Ru(III)(mu-NC)Mn(I)(CO)(dppm)2-trans][PF6]3.5Me2CO and [(H3N)5Ru(III)(mu-NC)Mn(I)(CO)2{P(OEt)3}(dppm)-trans][PF6]3.4Me2CO, between the amine groups (the H-bond donors) at the Ru(III) site and the oxygen atoms of solvent molecules or the fluorine atoms of the [PF6]- counterions (the H-bond acceptors).

Immobilisation of electroactive macrocyclic complexes within titania films

The 4-carboxyphenyl-appended macrocyclic ligand trans-6,13-dimethyl-6-((4-carboxybenzyl)amino)-1,4,8,11-tetraazacyclotetradecane-6-amine (HL10) has been synthesised and complexed with Co(III). The mononuclear complexes [Co(HL10)(CN)]2+ and [CoL10(OH)]+ have been prepared and the crystal structures of their perchlorate salts are presented, where the ligand is bound in a pentadentate mode in each case while the 4-carboxybenzyl-substituted pendent amine remains free from the metal. The cyano-bridged dinuclear complex [CoL10-mu-NC-Fe(CN)5]2- was also prepared and chemisorbed on titania-coated ITO conducting glass. The adsorbed complex is electrochemically active and cyclic voltammetry of the modified ITO working electrode in both water and MeCN solution was undertaken with simultaneous optical spectroscopy. This experiment demonstrates that reversible electrochemical oxidation of the Fe(II) centre is coupled with rapid changes in the optical absorbance of the film.

Intervalence transfer in a new benzotriazolate bridged ruthenium-iron complex

The unsymmetrical dinuclear ruthenium–iron complexes [(NH3)5Ru–bta–Fe(CN)5]n (where bta = benzotriazolate; n = –2, –1, 0) were prepared as solid sodium salts from [RuII(NH3)5(bta)]+ or [RuIII(NH3)5(bta)]2+ and [FeII(CN)5(H2O)]3– and characterized in aqueous solution by means of electrochemical and spectroelectrochemical methods. UV-vis, near-infrared, IR, and cyclic and differential pulse voltammetry data suggest that the related mixed valent species belong to a valence trapped formulation, featuring localized Ru(III) and Fe(II) oxidation states. In spite of the class II categorization in the Robin and Day scheme, this system shows a remarkable metal–metal electronic coupling, as deduced from an intense, low-energy, and very broad intervalence band in the near-IR region. In addition, the mixed valence state displays enhanced stabilization in relation to the isovalent state. The intervalence transfer properties are discussed on the basis of Hush's theory.Key words: ammineruthenium complexes, cyanoiron complexes, mixed valence, intervalence, benzotriazole, benzotriazolate.