Ruthenium monoterpyridine complexes with 2,6-bis(benzoxazol-2-yl)pyridine as an ancillary ligand: Synthesis, structure and spectral studies

Abstract

Ruthenium monoterpyridine complexes, [ 1] + and [ 2] 2+, with 2,6-bis(benzoxazol-2-yl)pyridine as an ancillary ligand, L, have been synthesized and characterized by UV–Vis, FT-IR and 1H NMR spectroscopic techniques. The formulations of the complexes were confirmed by the single crystal structure of their perchlorate salts. In both complexes, the Ru II center is hexa-coordinated in a distorted geometry. In complex [ 1] +, the ancillary ligand L behaves as a bidentate ligand; in [ 2] 2+, however, it binds the metal center as a tridentate ligand. The central pyridine nitrogen of terpyridine (N p,trpy) is in a cis position with respect to the central pyridine nitrogen of the ancillary ligand (N p,benz) in complex [ 1] + and in a trans-position in complex [ 2] 2+. The cis orientation of N p,trpy and N p,benz in complex [ 1] + forces L to behave as bidentate. The quasi-reversible Ru II/Ru III couple appears at 0.90 and 1.44 V versus SCE in the case of complex [ 1] + and [ 2] 2+, respectively. [ 1] +, in the presence of aqueous AgNO 3, affords [ 2] 2+ through an intramolecular dissociative interchange pathway.