Ruthenium(II) complexes of α-diimines:: synthesis, spectral characterisation, electrochemical properties and single-crystal X-ray structure of bis(2,2′-bipyridine){1-benzyl-2-(p-tollylazo)imidazole}-ruthenium(II) perchlorate

Mixed-ligand tris-chelates, [Ru(bpy)(2)(RaaiR')](ClO4)2 . H2O (bpy = 2,2'-bipyridine; RaaiR' = 1-alkyl-2-(arylazo)imidazole) have been synthesized by a silver-assisted route [Ru(bpy)(2)Cl-2 + RaaiR' + AgNO3 + NaClO4/Ru(bpy)(2)Cl-2 + [Ag(RaaiR')(2)](ClO4)]. The structures of the complexes have been supported by the single-crystal X-ray diffraction study and the stereochemistry are assessed by H-1 NMR spectral data. All the complexes show two metal-to-ligand charge transfer (MLCT) transitions in the visible region at ca. 400 and 500 nm and their emission spectra are also described here. Cyclic voltammetric studies exhibit high-potential Ru-III/II (1.4 V vs. SCE) and three successive ligand reductions at negative to SCE in acetonitrile solution. The difference in the first metal and successive ligand redox potentials are linearly correlated with the nu(CT) of MLCT band. (C) 2000 Elsevier Science Ltd. All rights reserved.