Photophysical behavior of transition metal complexes having interacting ligand localized and metal-to-ligand charge transfer states

Transition metal complexes having metal-to-ligand charge transfer (MLCT) excited states have been extensively investigated as sensitizers in light-induced electron transfer reactions. The photophysical behavior of the complexes is strongly dependent on the ligand serving as the electron acceptor. In systems where ligand localized triplet excited states are close in energy to the thermally equilibrated (MLCT)-M-3 state, strong interaction between the states is observed. This article provides an overview of the unique photophysical behavior observed in systems of this type. (C) 2004 Japanese Photochemistry Association. Published by Elsevier B.V. All rights reserved.