Electronic excitation spectrum of the photosensitizer [Ir(ppy)2(bpy)]+.

The vertical singlet-singlet and singlet-triplet electronic excitation energies of bis(2-phenylpyridinato-)(2,2'-bipyridine)iridium(III) (Ir(ppy)(2)(bpy)) are calculated on the basis of a comparative quantum chemical study using wave function methods such as CASSCF∕CASPT2 and density functional theory (TDDFT) with local and range-separated functionals. The TDDFT results show a strong dependence of the charge-transfer transition energies on the amount of the exact exchange in the functional. In general, TDDFT with range-separated functionals provides a good agreement with the experimental spectra. As a result a new assignment of the absorption spectrum of the title compound is proposed.