Unusually Short-Lived Solvent-Dependent Excited State in a Half-Sandwich Ru(II) Complexe Induced by Low-Lying 3MC States

A ruthenium complex with a half-sandwich geometry ([(p-cymene) Ru (Cl) (curcuminoid)]) was synthesized, character-ized and investigated regarding its ultrafast photophysics. These photophysical investigations of the complex revealed a weak and short-lived emission from the initially populated 1MLCT state and solvent dependent photo-induced dynamics, where the secondarily populated 3MC state is stabilized by non-polar solvents. Overall the decay of the 3dd-MC state to the ground state is completed within ps. This short excited state lifetime is in stark contrast to the typically observed long-lived 3MLCT states with lifetimes of ns or µs in unstrained, octahedral ru-thenium complexes, but is in good agreement with the findings for distorted octahedral complexes. This is pointing to the half-sandwich geometry as a new and easy approach to study these otherwise often concealed dd-states.