Unravelling the formation mechanism of alkynyl protected gold clusters: a case study of phenylacetylene stabilized Au144 molecules.

Despite recent progress in the preparation of alkynyl protected Au clusters with molecular purity (e.g., Na[Au25(C[triple bond, length as m-dash]CAr)18, Ar = 3,5-(CF3)2C6H3-, Au36(C[triple bond, length as m-dash]CPh)24, Au44(C[triple bond, length as m-dash]CPh)28, and Au144(C[triple bond, length as m-dash]CAr)60, Ar = 2-F-C6H4-), the formation mechanism still remains elusive. Herein, a new molecule-like alkynyl Au cluster was successfully prepared, and its formula was determined as Au144(PA)60 (PA = PhC[triple bond, length as m-dash]C-, phenylacetylene). In the formation of Au144(PA)60, the introduction of ethanol in post-synthesis treatment to manipulate the aggregation state of the precursor was found to play a critical role in producing the Au144 clusters. During the Au144(PA)60 formation process, the contents of PA, (PA)2 and (PA)4 were monitored by absorbance and gas chromatography-mass spectrometry (GC-MS), disclosing that Au144(PA)60 molecules were generated in sync with (PA)4. Finally, the formation mechanism of Au144(PA)60 molecules has been tentatively proposed, of which three major stages are involved. This study can shed light on the formation mechanism that may be exploited for the precise control of the synthesis of alkynyl protected coinage metal clusters.