Ruthenium (II) quinoline-azoimine complex: Synthesis, crystalline structures spectroelectrochemistry and catalytic properties

An octahedral ruthenium(II) complex with the general formula [RuII(Y)(bpy)Cl](ClO4) {Y= C6H5N=C(COCH3)-N=NC9H6N and bpy = 2,2′-bipyrdine} (1) was synthesized. The new ligand (Y) is coordinated to ruthenium via quinoline-N, imine-N and azo-N atoms. Both the novel complex 1 and the new ligand H2Y were structurally characterized by X-ray crystallography, spectroscopic (IR, UV–Vis and NMR spectroscopy) and electrochemical (cyclic voltammetry) techniques. The bonding in 1 and its published skeletal isomer [RuII(L1)(bpy)Cl](PF6) {L1 = C6H5N=N-C(COCH3) = NC9H6N5} (1A) has been analyzed using molecular orbital theory. The novel tridentate ligand (Y) stabilizes the Ru(II) oxidation state showing the Ru(III/II) couple at 1.05 V vs. Cp2Fe/Cp2Fe+. The potential use of 1 as a catalyst for hydrogenation of α, β-unsaturated aldehyde has been investigated. UV/Vis and IR-spectroelectrochemistry on complex 1 were performed.