Dinuclear Ru/Ni, Ir/Ni, and Ir/Pt Complexes with Bridging Phenanthroline-5,6-dithiolate: Synthesis, Structure, and Electrochemical and Photophysical Behavior

We report the synthesis and full characterization of dinuclear complexes with the bridging ligand phenanthroline-5,6-dithiolate (phendt2–) featuring the [Ru­(bpy)2]2+ or Ir­(ppy)2]+ fragment at the diimine donor center and the [Ni­(dppe)]2+ or [Pt­(phen)]2+ complex moiety at the dithiolate group. The molecular structures of the mononuclear complexes [(C5H5)2Ti­(S,S′-phendt)] and [(ppy)2Ir­{N,N′-phendt-(C2H4CN)2}]­(PF6) as well as the dinuclear complex [(C5H5)­(PPh3)­Ru­(phendt)­Ni­(dppe)]­(PF6) determined by X-ray diffraction (XRD) studies are compared. Photophysical studies with mononuclear [(bpy)2Ru­{phendt-(C2H4CN)2}]2+ and [(ppy)2Ir­{phendt-(C2H4CN)2}]+ as well as dinuclear [(bpy)2Ru­(phendt)­Ni­(dppe)]2+ and [(ppy)2Ir­(phendt)­Ni­(dppe)]+ uncovered an effective luminescence quenching in the dinuclear complexes. Lifetime measurements at room temperature, steady-state measurements at low temperature, electrochemical investigations, and DFT calculations provide evidence for a very efficient energy transfer from the Ru/Ir to the Ni complex moiety with a rate constant k > 5 × 109 s–1. In comparison, the [Ru]­phendt­[Ni] complex displays a higher quenching efficiency with reduced excited state lifetime, whereas the [Ir]­phendt­[Ni] complex is characterized by an unaltered lifetime of the thermally equilibrated excited state.本工作报道了以菲咯啉-5,6-二硫醇盐（phenanthroline-5,6-dithiolate，缩写phendt²⁻）为桥联配体的双核配合物的合成与全面表征，该类配合物在二亚胺给体中心带有[Ru(bpy)₂]²+或[Ir(ppy)₂]+片段，在二硫醇盐位点结合有[Ni(dppe)]²+或[Pt(phen)]²+配合物单元。本文还对通过X射线衍射（X-ray diffraction，XRD）测试确定分子结构的单核配合物[(C₅H₅)₂Ti(S,S'-phendt)]与[(ppy)₂Ir{N,N'-phendt-(C₂H₄CN)₂}](PF₆)，以及双核配合物[(C₅H₅)(PPh₃)Ru(phendt)Ni(dppe)](PF₆)的结构进行了对比分析。针对单核配合物[(bpy)₂Ru{phendt-(C₂H₄CN)₂}]²+、[(ppy)₂Ir{phendt-(C₂H₄CN)₂}]+，以及双核配合物[(bpy)₂Ru(phendt)Ni(dppe)]²+与[(ppy)₂Ir(phendt)Ni(dppe)]+开展的光物理研究显示，双核配合物中存在显著的发光淬灭效应。室温下的激发态寿命测试、低温稳态光谱测试、电化学研究以及密度泛函理论（Density Functional Theory，DFT）计算结果证实，Ru/Ir单元向Ni配合物单元的能量转移效率极高，速率常数k > 5×10⁹ s⁻¹。对比结果表明，[Ru]-phendt-[Ni]配合物的淬灭效率更高，且激发态寿命更短；而[Ir]-phendt-[Ni]配合物的热平衡激发态寿命未发生明显变化。