Sequential Dihydrogen Desorption from Hydride-Protected Atomically Precise Silver Clusters and the Formation of Naked Clusters in the Gas Phase

Abstract

We report the formation of naked cluster ions of silver of specific nuclearities, uncontaminated by other cluster ions, derived from monolayer-protected clusters. The hydride and phosphine co-protected cluster, [Ag₁₈(TPP)₁₀H₁₆]²⁺ (TPP, triphenylphosphine), upon activation produces the naked cluster ion, Ag₁₇⁺, exclusively. The number of metal atoms present in the naked cluster is almost the same as that in the parent material. Two more naked cluster ions, Ag₂₁⁺ and Ag₁₉⁺, were also formed starting from two other protected clusters, [Ag₂₅(DPPE)₈H₂₂]³⁺ and [Ag₂₂(DPPE)₈H₁₉]³⁺, respectively (DPPE, 1,2-bis(diphenylphosphino)ethane). By systematic fragmentation, naked clusters of varying nuclei are produced from Ag₁₇⁺ to Ag₁⁺ selectively, with systematic absence of Ag₁₀⁺, Ag₆⁺, and Ag₄⁺. A seemingly odd number of cluster ions are preferred due to the stability of the closed electronic shells. Sequential desorption of dihydrogen occurs from the cluster ion, Ag₁₇H₁₄⁺, during the formation of Ag_n⁺. A comparison of the pathways in the formation of similar naked cluster ions starting from two differently ligated clusters has been presented. This approach developed bridges the usually distinct fields of gas-phase metal cluster chemistry and solution-phase metal cluster chemistry. We hope that our findings will enrich nanoscience and nanotechnology beyond the field of clusters.

Keywords: Ag17+; Ag17H14+; dihydrogen; gas-phase clusters; mass spectrometry; monolayer-protected clusters; naked clusters; nanomaterials.