Vogler, Arnd and Kunkely, Horst
Optical Ligand to Ligand Charge Transfer of Metal Complexes Including Ligand-Based Mixed-Valence Systems.
Comments on Inorganic Chemistry 9 (3), pp. 201-220.
Other URL: http://www.informaworld.com/smpp/content~db=all~content=a756804210
The electronic spectra of metal complexes which contain a reducing and an oxidizing ligand (Lred-M-Lox) are characterized by ligand to ligand charge transfer (LLCT) absorptions. A specific form of Lred-M-Lox 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.