Synthesis, structure, redox behavior, catalytic activity and DFT study of a new family of ruthenium(III)1-(arylazo)naphtholate complexes

Abstract

Treatment of [RuCl2(DMSO)4] with 1-(arylazo)naphthol ligands in benzene under reflux afford the air-stable new ruthenium(III) complexes with general composition [Ru(L-R)3] (L = bidentate O, N donor; R = H, CH3, OCH3, Br, NO2) in good yield. The 1-(arylazo)naphthol ligands behave as tris-bidentate O, N donors via naphtholic proton and azo nitrogen. The molecular and electronic structure of the complexes have been established by elemental analysis and spectral (FT-IR, UV–vis & EPR) methods. DFT calculations were also carried out on the complexes 1 and 3 along with X-ray crystallized geometry of complex 5. These complexes in dichloromethane solution show intense ligand-to-metal charge transfer (LMCT) transitions in the visible region. The absorption and g-tensor value of these complexes (1, 3 & 5) were also computed and compared along with the available experimental results. The redox behavior of the complexes has been investigated by cyclic voltammetry and the potentials are observed with respect to the electronic nature of substituents (R) in the 1-(arylazo)naphthol ligands. These complexes have shown great promise as catalysts for the conversion of aldehydes to primary amides in good yield.