Optical Ligand to Ligand Charge Transfer of Metal Complexes Including Ligand-Based Mixed-Valence Systems

Abstract

The electronic spectra of metal complexes which contain a reducing and an oxidizing ligand (L_red–M–L_ox) are characterized by ligand to ligand charge transfer (LLCT) absorptions. A specific form of L_red–M–L_ox complexes are ligand-based mixed-valence (LBMV) compounds which contain the same ligand in two different redox states. In this case the ligand-ligand interaction may lead to a partial or even complete electronic delocalization between the reduced and oxidized form of the ligands. As a consequence, the “LLCT” transition loses its CT character since it takes place between delocalized orbitals.

Key Words:

• mixed-valence complexes
• electronic spectra
• optical electron transfer