Direct observation of a 1MLCT state by ultrafast transient absorption spectroscopy in Mo2(O2C-9-anthracene)4.

We have observed the excited-state dynamics of Mo2(O2C-9-anthracene)4 in THF using ultrafast transient UV/vis absorption spectroscopy. Following excitation at 514.5 nm into the metal-to-ligand charge-transfer (MLCT) state, transient absorption bands of the 1MLCT state appear at 410 and 610 nm. We assign these features to the 1MLCT state, which has a lifetime of approximately 10 ps. The decay of 1MLCT is accompanied by the formation of the triplet 3MLCT state, with an absorption band peaking at 410 nm. Excitation at 347 nm populates directly the ligand-centered (LC) state. From the rise of the 1MLCT band, the lifetime of the 1LC state is estimated to be less than 1 ps.