Application of time-resolved near-infrared spectroscopy (TRNIR) to the metal-to-ligand charge transfer (MLCT) excited state(s) of Os(phen)32+

Application of time-resolved near-infrared spectroscopy (TRNIR) to Os(phen)32+ in CD3CN, following visible (450 nm) laser flash excitation, reveals an absorption feature at ν¯max=5460cm-1 (εmax ⩾ 5000 M−1 cm−1, Δν¯1/2=1840cm-1) for the MLCT excited state Os(phen)32+∗. 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.