Ruthenium(II) Bipyridyl Complexes with CC* Cyclometalated Mesoionic Carbene Ligands

The synthesis of four 2,2'-bipyridyl ruthenium(II) complexes with cyclometalating mesoionic 1,2,3-triazolylidene ligands via their respective p-cymene ruthenium(II) precursors is presented. Solid-state structures confirm the formation of the proposed complexes, which were characterized by UV/vis and electrochemical experiments as well as time-dependent DFT calculations including NTO analysis. The title motif shows improved photophysical properties compared to structurally related ruthenium(II) complexes with (CC)-C-boolean AND* cyclometalating imidazole-based N-heterocyclic carbene ligands. Due to their electronic properties, the presented dyes are promising candidates for an application in dye-sensitized solar cells.