Superatomic Signature and Reactivity of Silver Clusters with Oxygen: Double Magic Ag17–with Geometric and Electronic Shell Closure

Abstract

Understanding the stability and reactivity of silver clusters toward oxygen provides insights to design new materials of coinage metals with atomic precision. Herein, we report a systematic study on anionic silver clusters, Agn− (n = 10–34), by reacting them with O2 under multiple-collision conditions. Mass spectrometry observation presents the odd–even alternation effect on the reaction rates of these Agn− clusters. A few chosen clusters such as Ag13− and Ag17-19− hold up in the presence of excessive oxygen gas reactants. First-principles calculation results reveal that the chemical stability of D4d Ag17− is associated with its symmetric ellipsoidal structure and the electronic shell closure of superatomic orbitals (1S2| 1P4|1P2|1D4|1D6||2S0). This results in 17c-2e multicenter bonding and a large highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap, the highest electron detachment energy and incremental binding energy among all the studied Agn− clusters, as well as the smallest O2 -binding energy and least charge transfer from Ag to O2. We fully demonstrate the superatomic signature of these silver clusters and emphasize the unique Ag17– with both geometric and electronic shell closure, shedding light on the 18e stability for the coinage of metal clusters. The superatomic characteristics are also disclosed for Ag16−, Ag18−, and Ag32− clusters.