Zwitterionic Thiolate-Protected Ag₂₂(0/I) and Ag₂₀(I) Clusters: Assembly, Structural Characterization, and...

Zwitterionic thiolate ligands have the potential to introduce novel assembly modes and functions for noble metal clusters. However, their utilization in the synthesis of silver clusters remains understudied, particularly for the clusters containing reductive Ag(0) species. In this article, we report the first synthesis of a mixed-valence silver(0/I) cluster protected by zwitterionic Tab as thiolate ligands (Tab = 4-(trimethylammonio)benzenethiolate), denoted as [Ag₂₂(Tab)₂₄](PF₆)₂₀·16CH₃OH·6Et₂O (Ag·16CH₃OH·6Et₂O), alongside an Ag(I) cluster [Ag₂₀(Tab)₁₂(PhCOO)₁₀(MeCN)₂(H₂O)](PF₆)₁₀·11MeCN (Ag·11MeCN). Ag has a distinct hierarchical supratetrahedral structure with a central {Ag₆} kernel surrounded by four [Ag₄(Tab)₆]⁴⁺ units. High-resolution electrospray ionization mass spectra demonstrate that Ag has two free electrons, indicating a superatomic core. Ag has a drum-like [Ag₁₂(Tab)₆(PhCOO)₆(H₂O)]⁶⁺ inner core capped by two tetrahedral-like [Ag₄(Tab)₃(PhCOO)₂(MeCN)]²⁺ units. Ag can be transformed into Ag after its reaction with NaBH₄ in solution. Antibacterial measurements reveal that Ag has a significantly lower minimum inhibitory concentration than that of the Ag cluster. This work not only extends the stabilization of silver(0/I) clusters to neutral thiol ligands but also offers new materials for the development of novel antibacterial materials.