Structurally Well-Defined Water-Soluble Gold Nanoclusters from Esterified Precursors and Their Photothermal Performance.

It is challenging to determine the structures of water-soluble metal nanoclusters due to the difficulty of their crystallization in aqueous media. As a consequence, the structures of many water-soluble nanoclusters are usually inferred from indirect models, which complicates the understanding of their structure-property relationships. We have developed a facile method to synthesize water-soluble gold nanoclusters with well-defined structures from esterified precursors. [C19H18N3][Au25(3-MeOOCC6H4C2)18] (Au25-COOMe) has been synthesized using 3-methoxycarbonyl phenylacetylide as the protecting ligand, and its structure has been determined with single-crystal X-ray diffraction. These oil-soluble clusters can be converted to water-soluble Au25-COONa in more than 90% yield via mild alkaline hydrolysis. Owing to the preservation of the Au25 metal core and superatomic electronic structure, the highly efficient photothermal performance of Au25-COOMe can be extended to water-soluble Au25-COONa. We present a potentially generalizable strategy that provides a viable route to reduce reliance on indirect structural models in studies of water-soluble gold nanoclusters.