Toward a Quantitative Understanding of Dipole-Moment Changes in Charge-Transfer Transitions: Electroabsorption Spectroscopy of Transition-Metal Complexes

This paper reports results for metal-to-ligand charge transfer (MLCT) and ligand-to-metal charge transfer (LMCT) absorption bands of Ru(II) and Ru(III) complexes and shows that the dipole-moment changes can be understood in terms of a two-state model which considers polarization, induced-dipole, and delocalization effects. In summary, the change in the charge of the metal center produced by charge-transfer excitation results in a change in ligand polarization which reduces the expected dipole-moment change. It is shown that including this effect, together with the effect of the permanent dipoles of the NH{sub 3} ligands, results in encouragingly good agreement with the predictions of a two-state model for MLCT and LMCT transitions. 22 refs.