Solid‐State Luminescence of AuCuAlkynyl Complexes Induced by Metallophilicity‐Driven Aggregation

A new series of homoleptic alkynyl complexes, [{Au 2 Cu 2 (C 2 R) 4 } n ] (R=C 3 H 7 O ( 1 ), C 6 H 11 O ( 2 ), C 9 H 19 O ( 3 ), C 13 H 11 O ( 4 )), were obtained from Au(SC 4 H 8 )Cl, Cu(NCMe) 4 PF 6 , and the corresponding alkyne in the presence of a base (NEt 3 ). Complexes 1 – 4 aggregate upon crystallization into polymeric chains through extensive metallophilic interactions. The cluster that contains fluorenolyl functionalities, C 13 H 9 O ( 5 ), crystallizes in its molecular form as a disolvate, [Au 2 Cu 2 (C 2 C 13 H 9 O) 4 ] ⋅ 2 THF. The substitution of weakly bound THF molecules with pyridine molecules leads to the complex [Au 2 Cu 2 (C 2 C 13 H 9 O) 4 ] ⋅ 2 py ( 6 ), thus giving two polymorphs in the solid state. Such structural diversity is established through metal‐chain and hydrogen‐bond formation, which depends on the stereochemical characteristics of the organic ligands. More interestingly, this solid‐state structural arrangement affords good emission properties, such as intensity and spectroscopic profile, which are otherwise very weakly emissive in solution. Metallophilic aggregation of the {Au 2 Cu 2 } cluster units, as observed in the crystals, results in dramatic enhancement of the room‐temperature phosphorescence, thereby reaching a maximum quantum efficiency of 95 % ( 4 ). A theoretical approach further indicates a synergistic effect of the array of the metal chain upon aggregation, which greatly enhances the spin‐orbit coupling and, hence, the phosphorescence, thereby opening up a new direction in the field of aggregate‐enhanced emission.