Ruthenium(II) Bipyridyl Complexes with Cyclometalated NHC Ligands.

We present the synthesis and characterization of novel cyclometalated ruthenium N-heterocyclic carbene (NHC) complexes of the general formula [Ru(C^C*)(bpy)2]PF6 (bpy = 2,2'-bipyridine), with the C^C* ligand being based on different 1-phenylimidazoles. They were synthesized in a one-pot procedure starting from the corresponding p-cymene NHC complexes [Ru(C^C*)(p-cymene)Cl]. Their structural, spectroscopic, and electrochemical properties were investigated by NMR, X-ray, UV/vis, and CV, as well as density functional theory methods. Because of the stronger electron-donating carbene ligands, these complexes represent a new class of bisheteroleptic dyes with improved photophysical and electrochemical properties.