ABSTRACT 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, Au 13 @Au 3 ‐Cl and Au 9 Cu 4 @Au 3 ‐Cl , stabilized by a tridentate phosphine (NP 3 ) metalloligand. Both adopt an unprecedented “Au 9 M 4 (Au/Cu) icosahedron + Au 3 crown” configuration and exhibit high solid‐state PLQYs of 44.5% and 38.9%, respectively. In contrast, replacing NP 3 with a monophosphine ligand (BPP) affords Au 9 Cu 4 ‐Cl lacking the Au 3 crown, with a dramatically reduced PLQY of 0.6%, highlighting the crucial roles of NP 3 and the Au 3 crown in boosting luminescence. Distinct photophysical behaviors are observed: Au 13 @Au 3 ‐Cl shows phosphorescence, while Au 9 Cu 4 @Au 3 ‐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 Au 9 Cu 4 ‐Cl . Coordinating anion substitution also modulates emission, with iodide promoting TADF in Au 13 @Au 3 ‐I . Moreover, the NP 3 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.
Tang et al. (Tue,) studied this question.