Au 38 (SPh) 24 : Au 38 Protected with Aromatic Thiolate Ligands

Au (SR) is one of the most extensively investigated gold nanomolecules along with Au (SR) and Au (SR) . However, so far it has only been prepared using aliphatic-like ligands, where R = -SC H , -SC H and -SCH CH Ph. Au (SCH CH Ph) when reacted with HSPh undergoes core-size conversion to Au (SPh) , and existing literature suggests that Au (SPh) cannot be synthesized. Here, contrary to prevailing knowledge, we demonstrate that Au (SPh) can be prepared if the ligand exchanged conditions are optimized, under delicate conditions, without any formation of Au (SPh) . Conclusive evidence is presented in the form of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), electrospray ionization mass spectra (ESI-MS) characterization, and optical spectra of Au (SPh) in a solid glass form showing distinct differences from that of Au (S-aliphatic) . Theoretical analysis confirms experimental assignment of the optical spectrum and shows that the stability of Au (SPh) is not negligible with respect to that of its aliphatic analogous, and contains a significant component of ligand-ligand attractive interactions. Thus, while Au (SPh) is stable at RT, it converts to Au (SPh) either on prolonged etching (longer than 2 hours) at RT or when etched at 80 °C.