The properties of some organic molecules as free species and as ligands in ruthenium(II) complexes

The electron affinities and polarizabilities of imidazole, pyrazine, 2,2′-bipyridine and o-benzoquinone diimine were calculated by the density functional method. It was demonstrated that in transition metal complexes the π∗-accepting ability of the ligand is determined mainly by its electron affinity. Our calculations showed that o-benzoquinone diimine (bqdi) is a very strong acceptor of π electrons, but that this ability depends on the composition of the complex.