Application of time-resolved near-infrared spectroscopy (TRNIR) to the metal-to-ligand charge transfer (MLCT) excited state(s) of

Application of time-resolved near-infrared spectroscopy (TRNIR) to Os ( phen ) 3 2 + in CD3CN, following visible (450 nm) laser flash excitation, reveals an absorption feature at ν ¯ max = 5460 cm - 1 (emax ⩾ 5000 M−1 cm−1, Δ ν ¯ 1 / 2 = 1840 cm - 1 ) for the MLCT excited state Os ( phen ) 3 2 + ∗ . Based on an electronic structure model, including spin–orbit coupling, the absorption is tentatively assigned to three overlapping ligand-to-ligand charge transfer (LLCT) bands two of which have dπ → dπ interconfigurational character. This assignment is consistent with the results of a solvent dependence study and an analysis of predicted band energies.