Bis(2,2′-bipyridine)ruthenium(II) complexes with salicylaldehyde and its 5-substituted derivatives - Synthesis, structure, and properties

Abstract

Ruthenium(II) mixed-ligand complexes having the general formula [Ru(bpy)2(salR)]PF6 derived from 2,2′-bipyridine and salicylaldehyde or its 5-substituted derivatives (HsalR, H stands for the dissociable phenolic-OH proton; R = H, OMe, tBu, Cl, NO2) are described. Characterisation of the complexes were performed by using microanalysis, cyclic voltammetry and various forms of spectroscopy such as infrared, electronic and 1H NMR. Diamagnetic character of the complexes is consistent with low-spin ruthenium(II) system. In solution, each of them behaves as 1:1 electrolyte. Crystal structures of [Ru(bpy)2(salH)]PF6 and [Ru(bpy)2-(salCl)]PF6 have been determined. In solid state, salR- ligand exists as the intermediate of the normal phenolate structure and a quinonoid structure. The complexes display the Ru(III)-Ru(II) couple in the potential range 0.61-0.84 V (vs. Ag/AgCl) in acetonitrile solutions. The potential of this couple is linearly related to the Hammett constant of the substituent R.