Dicarboxylic Acids Induced Tandem Transformation of Silver Nanocluster.

Structural transformation of metal nanoclusters (NCs) is of great ongoing interest regarding their synthesis, stability, and reactivity. Although sporadic examples of cluster transformations have been reported, neither the underlying transformation mechanism nor the intermediates are unambiguous. Herein, we have synthesized a flexible 54-nuclei silver cluster () by combining soft (BuC≡C) and hard (PrCOO) ligands. The existence of weakly coordinated PrCOO enhances the reactivity of , thus facilitating the dicarboxylic acid to induce structural transformation. X-ray structural analyses reveal that transforms to Ag cluster-based 2D networks ( and ) induced by Hsuc (succinic acid) and Hglu (glutaric acid), whereas with Hpda (2,2'-(1,2-phenylene)diacetic acid), a discrete Ag cluster () is isolated. The key intermediate that emerges during the self-dissociation of was isolated by using cryogenic recrystallization and characterized by X-ray crystallography. The "tandem transformation" mechanism for the structure evolution from to is established by time-dependent electrospray ionization mass spectrometry (ESI-MS) and UV-vis spectroscopy. In addition, the catalytic activity in the 4-nitrophenol reduction follows the sequence > > > due to more bare silver sites on the surface of the Ag cluster unit. Our findings not only open new avenues to the synthesis of silver NCs but also shed light on a better understanding of the structural transformation mechanism from one cluster to another or cluster-based metal-organic networks induced by dicarboxylates.