Synthesis, characterization, polarized luminescence properties of platinum(ii) complexes having a rod-like ligand

摘要

We have synthesized a series of platinum (Pt) complexes having a rod-like ligand: 'Pt(F _2PPy)acac', 'Pt(12F _2PPy)acac', and 'Pt(12F _2PPyO4)acac'. The crystal form of Pt(12F _2PPy)acac was successfully determined to be triclinic by single-crystal X-ray structural analysis. The molecules were parallelly aligned in the unit cell. Monomer and excimer emissions of Pt(12F _2PPy)acac were observed in hexane solution, poly(methyl methacrylate) film, and various nematic LCs. Homogeneous LC cells with the Pt complex/LC mixtures exhibited polarized optical emission resulting from monomer and excimer states. The PL intensity perpendicular to the orientation direction was higher than the parallel one in the whole wavelength region of the Pt complex and the polarization ratio of the excimer was higher than that of the monomer. The polarization ratios of the excimers were estimated to be 1.4-2.5 in nematic LC at room temperature, and decreased gradually with increasing temperature. The polarization ratios of Pt(12F _2PPyO4)acac were higher than those of Pt(F _2PPy)acac and Pt(12F _2PPy)acac in all the LCs.