Synthesis, characterization and photophysical properties of the pincer platinum(II) complexes with m-bis(benzimidazol-2′-yl)benzene ligand

The reaction of 2,2′-(1,5-dibutoxy-2,4-phenylene)bis(1-phenyl-1H-benzo[d]imidazole) (1) with K2PtCl4 in refluxing HOAc afforded the pincer Pt(II) chloride complex 2. Treatment of 2 with KI gave the corresponding Pt(II) iodide complex 3. While reaction of 2 with 4-(methoxy)phenylacetylene in the presence of NaOH easily produced the Pt(II) acetylide complex 4. All of the new compounds have been well characterized by elemental analysis (HRMS for 1), NMR, and IR spectra. Additionally, the molecular structures of Pt(II) complexes 2–4 have been determined by X-ray single-crystal diffraction. The electronic absorption and photoluminescent properties of Pt(II) complexes 2–4 have been investigated. The same level time-dependent density functional theory (TD-DFT) calculations were carried out by using the Gaussian 09 program package. All of the platinum complexes investigated in this study have exhibited luminescence in CH2Cl2 solution, in the solid state and in glass 2-MeTHF solution at 77 K, displaying vibronically structured emission profiles. The luminescence quantum yields in CH2Cl2 solution are 0.05–0.06 and the emission lifetimes are in microsecond range.

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