Multifaceted Molecular Design Enables Comprehensive Luminescence Modulation in Metalloligand-Stabilized Gold Nanoclusters

Photoluminescent metal nanoclusters hold promise for optoelectronics, photonics, and chemosensing, yet systematic modulation of their emission within a single system remains challenging. Here, we report two isostructural clusters, Au₁₃@Au₃-Cl and Au₉Cu₄@Au₃-Cl, stabilized by a tridentate phosphine (NP₃) metalloligand. Both adopt an unprecedented “Au₉M₄ (Au/Cu) icosahedron + Au₃ crown” configuration and exhibit high solid-state PLQYs of 44.5% and 38.9%, respectively. In contrast, replacing NP₃ with a monophosphine ligand (BPP) affords Au₉Cu₄-Cl lacking the Au₃ crown, with a dramatically reduced PLQY of 0.6%, highlighting the crucial roles of NP₃ and the Au₃ crown in boosting luminescence. Distinct photophysical behaviors are observed: Au₁₃@Au₃-Cl shows phosphorescence, while Au₉Cu₄@Au₃-Cl exhibits thermally activated delayed fluorescence (TADF), confirmed by femtosecond transient absorption spectroscopy. The role of Cu doping is further supported by the TADF activity of Au₉Cu₄-Cl. Coordinating anion substitution also modulates emission, with iodide promoting TADF in Au₁₃@Au₃-I. Moreover, the NP₃ ligand confers reversible protonation-induced luminescence switching, enabling chemosensing potential. Collectively, these findings demonstrate a comprehensive investigation of TADF behavior and luminescence modulation in atomically precise metal nanoclusters, systematically engineered through heteroatom doping of the inner core, ligand design and anion exchange at the coordination surface, and outer-sphere complexation and protonation.