Photochemical synthesis of Ag12Cu7 nanocluster with cuprophilicity-related long-lived phosphorescence

Atomically precise alloyed nanoclusters (NCs) have attracted widespread attention due to synergistic effect but their controllable synthesis remains a challenge. Among them, Ag–Cu alloyed NCs are particularly limited due to significant difference in redox potential, and it is highly desirable to develop controllable and mild synthesis methods. This work proves the feasibility of photochemical synthesis method for Ag₁₂Cu₇(4-^tBuPhC≡C)₁₄(Dpppe)₃Cl₃(SbF₆)₂ (Ag₁₂Cu₇) alloyed NC that exhibits remarkable ligand-supported cuprophilic interaction. Experimental and time-dependent UV–Vis spectroscopy first reveals that the formation of Ag₁₂Cu₇ is a step-by-step process, in which light induces the reduction of Ag⁺ to Ag₁₉ cluster containing two electrons, then CuCl incorporates into Ag NC to yield the target NC, providing an alternative pathway toward alloyed NCs. Remarkably, Cu···Cu interaction endows Ag₁₂Cu₇ with a strong long-lived red phosphorescence of 30 µs at room temperature, which is superior to the majority of Ag–Cu-alloyed NCs. Theoretical calculations indicate that the phosphorescence originates from cluster-centered triplet–excited state modified by cuprophilic interactions, mixed with ligand-to-metal charge transfer.