Excited state properties of organometallics based on interligand interactions between aromatic ligands

Excited state properties of coordination compounds have been studied for many years. Surprisingly, rather little is known about excited states, which are based on intramolecular interligand interactions. There are two types of these interligand excited states. In homoleptic complexes, such as Mg(C5H5)2, ligand-ligand interaction creates new low-energy interligand states, which are comparable to intermolecular excimers of aromatic molecules. In heteroleptic complexes of the type (C7H7)M(C5H5), low-energy ligand-to-ligand charge transfer (LLCT) excited states are available. Various organometallic compounds, which are characterized by such interligand excited states, are discussed in this account.