Bimetallic Ru(II)-Ir(III) complexes with bridging 2,2′-bipyrimidine: Synthesis, structures and characterization

In this work, four bimetallic Ru(II)-Ir(III) complexes with the general formula [(bpy)(2)Ru(bpm)Ir(C<^>N)(2)](PF6)(3) (bpy = 2,2-bipyridine, bpm = 2,2 '-bipyrimidine, C<^>N = 2-phenylpyridinato (2), (2-p-tolyl)pyridinato (3), 2-(2,4-difluorophenyl)pyridinato (4), and 2-thienylpyridinato (5)) were synthesized. Complexes 2-5 were characterized by NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis. The structures of the complexes 2 and 4 were further confirmed by single-crystal X-ray diffraction analysis. All the complexes display strong absorption in the high-energy UV region assigned to intraligand (IL) transitions, and the lower energy bands are ascribed to metal-to-ligand charge transfer (MLCT) transitions. The reduction and oxidation behavior of the complexes 2-5 were examined by cyclic voltammetry. Variation of the ligands on Ir(III) center resulted in significant changes in electrochemical properties.