Strongly Luminescent Palladium(0) and Platinum(0) Diphosphine Complexes

The synthesis, structure, and photoluminescence of palladium(0) and platinum(0) complexes containing biarydiphosphines, biphep (biphep = 2,2‘-bis(diphenylphosphino)-1,1‘-biphenyl) and binap (binap = 2,2‘-bis(diphenylphosphino)-1,1‘-binaphthyl) have been studied. X-ray structure analysis of [Pt(biphep)2] revealed the distorted-tetrahedral geometry of the complex. The photophysical properties of the three complexes [Pd(biphep)2], [Pt(biphep)2],
and [Pd(binap)2] were investigated and compared with that of the previously reported [Pt(binap)2] complex. The
[Pd(biphep)2] complex shows the strongest luminescence with a high quantum yield (38%) and a long lifetime (3.2
μs) in a toluene solution at room temperature. The luminescence should be due to metal-to-ligand charge transfer
excited states. At room temperature, radiative rate constants of the four complexes show similar values. The
difference in the luminescent properties should reflect the different nonradiative rate constants of the complexes.
The temperature-dependence of the luminescence spectra and lifetime of the complexes were also discussed.

本研究针对含联芳基双膦配体的零价钯（palladium(0)）与零价铂（platinum(0)）配合物的合成、结构及光致发光性能展开系统探究，所涉及的配体包括联苯膦（biphep，即2,2'-双(二苯基膦基)-1,1'-联苯）与联萘膦（binap，即2,2'-双(二苯基膦基)-1,1'-联萘）。通过对[Pt(biphep)₂]配合物开展X射线结构分析，揭示了该配合物具有扭曲四面体几何构型。本研究对[Pd(biphep)₂]、[Pt(biphep)₂]与[Pd(binap)₂]三种配合物的光物理性能进行了表征，并与已有文献报道的[Pt(binap)₂]配合物展开对比分析。在室温甲苯溶液中，[Pd(biphep)₂]配合物展现出最强的发光性能，其量子产率高达38%，荧光寿命长达3.2微秒（μs）。该发光现象应归因于金属-配体电荷转移（metal-to-ligand charge transfer, MLCT）激发态。室温下，四种配合物的辐射跃迁速率常数数值相近，而发光性能的差异实则源于各配合物非辐射跃迁速率常数的不同。本研究同时探讨了配合物的发光光谱与寿命随温度的变化规律。