Manifestation of Geometric and Electronic Shell Structures of Metal Clusters in Intercluster Reactions

Monolayer protected clusters exhibit rich diversity in geometric and electronic structures. However, structure–reactivity relationships in these clusters are rarely explored. In this context, [Ag44(SR)30]4–, where −SR is an alkyl/aryl thiolate, is an interesting system due to its geometrically and electronically closed-shell structures and distinct charge states. We demonstrate that these structural features of [Ag44(SR)30]4– are distinctly manifested in its solution-state reaction with another cluster, [Au25(SR)18]−. Through this reaction, an alloy cluster anion, [Au12Ag32(SR)30]4–, evolves spontaneously as revealed by high-resolution electrospray ionization mass spectrometry. Ultraviolet–visible absorption spectroscopy and density functional theory calculations indicate that [Au12Ag32(SR)30]4– is formed by the substitution of all of the Ag atoms in the innermost icosahedral shell of [Ag44(SR)30]4– and the abundance is attributed to its higher stability due to closed geometric as well as electronic shell...