Toward Luminescence Vapochromism of Tetranuclear AuI–CuI Clusters

A family of triphosphine gold–copper clusters bearing aliphatic and hydroxyaliphatic alkynyl ligands of general formula [HC­(PPh2)3Au3Cu­(C2R)3]+ (R = cyclohexyl (1), cyclopentyl (2), But (3), cyclohexanolyl (4), cyclopentanolyl (5), 2,6-dimethylheptanolyl (6), 2-methylbutanolyl (7), diphenylmethanolyl (8)) was synthesized via a self-assembly protocol, which involves treatment of the (AuC2R)n acetylides with the (PPh2)3CH ligand in the presence of Cu+ ions and NEt3. Addition of Cl– or Br– anions to complex 8 results in coordination of the halides to the copper atoms to give neutral HC­(PPh2)3Au3CuHal­(C2COHPh2)3 derivatives (Hal = Cl (9), Br (10)). The title compounds were characterized by NMR and ESI-MS spectroscopy, and the structures of 1, 4, 7, and 8 were determined by single-crystal X-ray diffraction analysis. The photophysical behavior of all of the complexes has been studied to reveal moderate to weak phosphorescence in solution and intense emission in the solid state with a maximum quantum yield of 80%. Exposure of the solvent-free X-ray amorphous samples 8–10 (R = diphenylmethanolyl) to vapors of the polar solvents (methanol, THF, acetone) switches luminescence with a visible hypsochromic shift of emission of 50–70 nm. The vapochromism observed is tentatively ascribed to the formation of a structurally ordered phase upon absorption of organic molecules by the amorphous solids.

本研究合成了一系列通式为[HC(PPh₂)₃Au₃Cu(C₂R)₃]⁺的三膦配位金-铜团簇，其配体为脂肪族与羟基脂肪族炔基配体，其中R分别对应：环己基（化合物1）、环戊基（化合物2）、叔丁基（But，化合物3）、环己醇基（化合物4）、环戊醇基（化合物5）、2,6-二甲基庚醇基（化合物6）、2-甲基丁醇基（化合物7）、二苯甲醇基（化合物8）。该系列团簇通过自组装策略合成，具体过程为在Cu⁺离子与三乙胺（NEt₃）存在下，将(AuC₂R)ₙ炔化物与三(二苯基膦基)甲烷（(PPh₂)₃CH）配体进行反应。向配合物8中加入Cl⁻或Br⁻阴离子，可使卤化物与铜原子配位，得到中性衍生物HC(PPh₂)₃Au₃CuHal(C₂COHPh₂)₃（Hal=Cl对应化合物9、Br对应化合物10）。标题化合物通过核磁共振波谱（NMR）与电喷雾电离质谱（ESI-MS）进行表征，配合物1、4、7和8的结构通过单晶X射线衍射分析得以确定。对所有配合物的光物理行为展开研究后发现，其在溶液中呈现中等至偏弱的磷光发射，在固态下则具有强发射特性，最高量子产率可达80%。将无溶剂的X射线非晶态样品8~10（R=二苯甲醇基）置于极性溶剂（甲醇、四氢呋喃（THF）、丙酮）蒸气中时，其发光行为发生变化，发射峰呈现50~70 nm的明显蓝移。所观测到的蒸气致变色（vapochromism）现象初步归因于非晶态固体吸附有机分子后形成了结构有序的物相。