Excited state properties of [Pd0(NHC)(quinone)]2 with NHC = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene and quinone = 1,4-naphthoquinone

The carbene complex [Pd0(NHC)(quinone)]2with NHC = 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene and quinone = 1,4-naphthoquinone shows two long-wavelength absorptions at 312 and 399 nm which are assigned to (NHC→quinone) LLCT and (Pd0 → quinone) MLCT transitions. The MLCT state is not reactive, but emissive (λmax = 564 nm at 77 K). At r.t., the complex undergoes a photoredox decomposition which is initiated by the LLCT state.