N-coordination-driven anchoring of M2 dimers (M = Cu, Ag) on Au6 cluster: structural evolution and enhanced photoluminescence.

Precise alloying of gold clusters is a cornerstone for tailoring their structures and properties; however, atomic-level control over heterometal placement remains elusive due to the inherently stochastic nature of conventional synthetic routes. Herein, we report a coordination-driven alloying strategy that enables site-specific grafting of M2 dimers (M = Cu, Ag) onto a Au6 core stabilized by pyridyl-bridged diphosphines. Single-crystal X-ray analysis reveals that pyridyl-N → M coordination governs the formation of these Au6M2 clusters, with Au6Cu2 adopting a markedly more compact framework. While heterometal incorporation slightly perturbs the absorption bands associated with frontier orbitals, it remarkably enhances near-infrared photoluminescence in solution, affording up to a 150-fold increase in quantum yield for Au6Cu2. Theoretical analyses identify the heterometals as electron-deficient, weakly interacting species, indicating a ligand-governed surface anchoring mode rather than core-level substitution. This work establishes coordination-driven postsynthetic alloying as a powerful and deterministic strategy for atomically precise engineering of gold-based alloy clusters via controlled heterometal anchoring.