Capturing Ag6 Inner-Core Contraction in Inorganic-Template-Stabilized Ag78 Nanoclusters

Resolving how subangstrom changes in a metal core affect electronic structure and photophysical properties in high-nuclearity silver nanoclusters (NCs) remains challenging, as inner-core variations are often coupled with changes in outer metal shells, surface coordination, or crystal packing. Here, we report a structurally homologous series of Ag78 NCs (Ag78-1-Ag78-4) sharing a common Ag6@Ag24@Ag48 metal architecture stabilized by an S2-/SO42- inorganic template framework. The inorganic template layer stabilizes the metal architecture and reduces structural perturbations from the outer coordination environment, allowing localized Ag6 contraction while largely retaining the overall metal-inorganic architecture. Removal of the central Cl- template in Ag78-1 produces a distinct inward contraction of the Ag6 core in Ag78-2, and surface chloride substitution further accesses more contracted structural states (Ag78-3 and Ag78-4). These structural evolutions are established by single-crystal X-ray diffraction and supported by ESI-MS. Steady-state spectroscopy reveals progressive modulation of low-energy absorption and emission behavior across the series. Theoretical calculations show that central Cl- removal and accompanying Ag6 contraction reorganize low-energy electronic states, and femtosecond transient absorption across the series reveals corresponding changes in excited-state relaxation dynamics. This work establishes an inorganic-template-stabilized Ag78 platform for correlating atomically resolved inner-core structural evolution with electronic structures and excited-state properties in high-nuclearity silver NCs.