Structure‐Dependent Photoluminescence and Chemiluminescence Emission Enhancement in Ag₂₅ Nanoclusters

Abstract Surface ligands crucially influence the structure and luminescence of metal nanoclusters (NCs). In this study, three [Ag₂₅(SPhCl)_16−xCl_x(DPPB)₆]²⁺ (x = 0 for Ag₂₅, x = 1 for Ag₂₅‐Cl, and x = 4 for Ag₂₅‐4Cl) featuring thiol and Cl ligand combinations are synthesized and investigated. Ag₂₅‐4Cl, which has the smallest number of rigid thiol ligands, exhibits the strongest photoluminescence (PL) and chemiluminescence (CL), and its PL quantum yield is 73.43% higher than that of Ag₂₅. Structural analysis indicates that Cl ligands, being smaller and less sterically hindering than thiols, compress the motif layer towards the core, reducing non‐radiative transitions and boosting radiative ones to enhance PL. All three NCs exhibit CL in the presence of singlet oxygen, demonstrating the ability of the NCs to react with radicals and scavenge them. CL and radical scavenging experiments show that Ag₂₅‐4Cl exhibits the highest CL and the lowest radical reaction ability, indicating that CL intensity of an NC depends more on its intrinsic luminescence ability and less on its ability to react with radicals. The regulation of luminescence by ligands and the CL and radical‐scavenging behavior of NCs are expected to be extended to other NC systems and related applications.