Microwave synthesis and electrospectrochemical study on ruthenium(II) polypyridine complexes

A microwave assisted simple method was developed to prepare various ruthenium(II) polypyridine complexes rapidly with a high yield. For example, [Ru(Hdpa)3](ClO4)2 was prepared from RuCl3·3H2O in a few minutes in more than 90% yield. The oxidation potentials were determined for over 50 Ru(II) polypyridine complexes in acetonitrile to estimate the electrochemical ligand (L) parameters, from which we calculated oxidation potentials of various polypyridine Ru complexes. A linear relation between calculated and observed values indicates the additivity of the ligand contribution to the Ru(III)/Ru(II) potential. Moreover, the linear relation between the average difference of 13C-NMR chemical shifts of 4,4′ carbon atoms of bipyridine ligands and oxidation potentials for the bis bipyridine complexes, [Ru(bpy)2L]2+, was found with respect to the π-donor/-acceptor properties of L. The relation can be explained by quantum mechanical calculation using gaussian-98.