Evolution of all-carboxylate-protected superatomic Ag clusters confined in Ti-organic cages

In this study, the size of the titanium organic cage was controlled to achieve the restricted growth from a single Ag(I) atom (Ag@Ti₅) to rare all-carboxylate-protected superatomic Ag cluster (Ag₆@Ti₆). The classical octahedral Ag₆⁴⁺ cluster with two delocalized electrons (2e) has been encapsulated in a Ti₆ organic cage, which shows high stability in air and dimethyformamide (DMF). Furthermore, larger 2e nested double-tetrahedra Ag clusters (Ag₈⁶⁺ and Ag₉⁷⁺) protected using a tetrahedral hollow metalloligand framework (Ag₈@Ti₄ and Ag₉@Ti₄) were obtained. Electrospray ionization mass spectrometry (ESI-MS) and density functional theory (DFT) calculations confirmed that there are two delocalized electrons on these small Ag clusters. This study provides a new form of protection for superatomic Ag clusters and provides a feasible strategy for the development of stable Ag clusters.