Exploring the photo-stability of the {Ru(py)4}2+ fragment

Abstract

Mononuclear Ru(II) tetrakis-pyridine species of general formula trans-[(Cl)Ru(py)4(X)]n+ (X = Cl-, MeCN and CO) are thermally inert toward ligand exchange reactions at room temperature, but undergo substitution under photolysis conditions. The carbonyl derivative trans-[(Cl)RuII(py)4(CO)]+ was specifically synthesized for this report by the direct reaction between trans-[(Cl)RuII(py)4(Solv)]+ and CO in acetone and isolated as a PF6- salt. Stationary photolysis experiments in MeCN allowed recording changes in the absorption profiles along time providing quantitative values for the quantum yields of the different photo-processes, which involve the consecutive loss of CO, MeCN or pyridine ligands. There is no evidence of photo-release of a chloride anion in none of the molecules under study. For X = CO and MeCN the photo-release of X is favored over the substitution of a pyridine molecule.