Excited-state dynamics of luminescent transition metal complexes with metallophilic and donor–acceptor interactions

Luminescent transition metal complexes have attracted much attention owing to their utilization in a variety of photochemical applications such as light-emitting devices, bioimaging and solar–energy conversion. The photofunctionalities of these complexes (e.g., emission color, quantum yield and lifetime) are broadly tunable owing to the presence of various electronic excited states originating in the metal center and ligand(s). Therefore, a huge number of luminescent transition metal complexes has been hitherto reported. It is quite important to understand the excited-state dynamics of the complexes including population change between the excited states, structural change and intersystem crossing. Since recent progress in the instrumental analysis enables direct observation of the excited-state dynamics, a variety of the processes in the excited state has been elucidated. In this review, the excited-state dynamics of luminescent transition metal complexes are highlighted in terms of metallophilic and donor–acceptor interactions.