Synthesis, Structural Characterization, and Luminescence Properties of Mono- and Di-Nuclear Platinum(II) Complexes Containing 2-(2-Pyridyl)-benzimidazole

Abstract The starting complex [Pt(Me)(DMSO)(pbz)] (1, pbz = 2-(2-pyridyl)benzimidazolate) was prepared by a known method using the reaction of [Pt(Me)2(DMSO)2] with Hpbz at room temperature. Reaction of 1 with an equivalent of a phosphine ligand gave the neutral mononuclear complexes [Pt(Me)(L)(pbz)] (2, L = PPh3 and 3, L =PPh2Me). Reaction of 1 with 0.5 equivalent of the linear diphosphine 1,1'–bis(diphenylphosphino)acetylene (dppac) gave the binuclear complex [Pt2(Me)2(μ-dppac)(pbz)2]. Each complex was fully characterized by NMR spectroscopy, X-ray single-crystal crystallography and mass spectrometry. The photophysical properties of the complexes were investigated under different conditions and interpretation was supported by TD-DFT calculations. The low-lying transitions in the absorption and emission spectra were assigned as having LLCT/MLCT (ligand to ligand charge transfer/metal to ligand charge transfer) character. We also describe the luminescence properties of [Pt(Me)(PPh3)(ppy)] and [Pt(Me)(PPh2Me)(ppy)] (ppy is 2-phenylpyridinate), the (N^C−) analogues of 2 and 3.