Ultrafast excited-state dynamics of photoisomerizing complexes fac-[Re(Cl)(CO)3(papy)2] and fac-[Re(papy)(CO)3(bpy)]+ (papy=trans-4-phenylazopyridine)

Laser pulse excitation of rhenium–carbonyl complexes with an azobenzene-type ligand populates a triplet intraligand excited state, which undergoes partial rotation around the NN bond, return to the ground state and isomerization in ca. 100ps. An intramolecular energy transfer from MLCT to IL excited state occurs in a bipyridine-containing complex with 3ps kinetics.