Effects of bromine-containing counterion salts in directing the structures of medium-sized silver nanoclusters

The preparation and structural determination of silver nanoclusters (especially the medium-sized Ag clusters) remain more challenging relative to those of their gold counterparts because of the comparative instability of the former. In this work, three medium-sized Ag clusters were controllably synthesized and structurally determined, namely, [Ag52(S-Adm)30Br4H20]2- (Ag52 for short), Ag54(S-Adm)30Br4H20 (Ag54 for short), and [Ag58(S-Adm)30Br4(NO3)2H22]2+ (Ag58 for short) nanoclusters. Specifically, the introduction of PPh4Br gave rise to the generation of Ag52 and Ag54 nanoclusters with homologous compositions and configurations, while the TOABr salt selected Ag58 as the sole cluster product, whose geometric structure was completely different from those of Ag52 and Ag54 nanoclusters. In addition, the optical absorptions and emissions of the three medium-sized silver nanoclusters were compared. The findings in this work not only provide three uniquely medium-sized nanoclusters to enrich the silver cluster family but also point out a new approach (i.e., changing the counterion salt) for the preparation of new nanoclusters with novel structures.