Subshell-Confined Symmetry Lowering and Prolonged Excited-State Dynamics in Large Silver Nanoclusters

Abstract Symmetry breaking has the potential to counteract the shortening of excited-state lifetimes with increasing nuclearity and metallicity but is difficult to accomplish in large nanoclusters, whose multishell frameworks are strongly coupled. Here, we report a four-shell silver nanocluster, Ag104, in which the principal reconstruction is concentrated in an Ag52S22 subsurface shell, and whose inner core and outer ligand-protected motifs retain closely similar topologies relative to its highly symmetric Ag100 analogue – a structurally related pair that enables the correlations accompanying localized symmetry distortion to be examined. The two clusters also differ in composition and thiolate substitution pattern, so the comparison probes coupled structural and electronic changes. Electronic-structure calculations and real-space charge analyses showed that subshell-confined symmetry breaking lifts electronic degeneracies, redistributes oscillator strength, and induces pronounced spatial charge separation, thereby reducing electron–hole overlap. Ultrafast transient absorption spectroscopy further revealed an unexpected order-of-magnitude increase in carrier lifetime from ∼500 ps in Ag100 to ∼5 ns in Ag104 and distinctly activated phonon-assisted relaxation in Ag100 compared to Ag104. This establishes a strategy for engineering large atomically precise nanoclusters with long-lived excited states.