Mixed ligand complexes of osmium(II)-2,2 '-bipyridine: synthesis, spectral characterization and electrochemical properties of bis-chelated-arylazoimidazole-bipyridine-osmium(II) and X-ray crystal structure of [(2,2 '-bipyridine)-bis-{1-methyl-2(p-tol

摘要

Reaction of ctc-OsBr2(RaaiR')(2) [RaaiR= 1-alkyl-2-(arylazo)imidazole, p-R-C6H4-N=N-C3H2-NN-1-R', where R = H (a), Me (b) Cl (c) and R'= Me (2) Et (3) and CH2Ph (4)] with 2,2-bipyridine (bpy) in presence of AgNO3 in EtOH followed by the addition of NH4PF6 afforded a mixed ligand complex [Os(bpy)(RaaiR')(2)](PF6)(2). The structure of the complex, in one case [Os(bpy)(Mea-aiMe)(2)](PF6)(2)(.)4H(2)O, has been confirmed by X-ray crystallography. The complexes are diamagnetic (low spin d(6), s = 0) and they show intense MLCT transition in the visible region (480-525 nm) and a weak transition at longer wavelength (>850 nm) in CH3CN solution. Cyclic voltammetry of the complexes show two metal oxidation, Os(II)/Os(III) at 0.72-0.76 V and Os(III)/Os(IV) at 1.34-1.42 V and three successive ligand reductions. (C) 2004 Elsevier B.V. All rights reserved.