Experimental Confirmation of a Topological Isomer of the Ubiquitous Au25(SR)18 Cluster in the Gas Phase

High-resolution electrospray ionization ion mobility mass spectrometry has revealed a gas-phase isomer of the ubiquitous, extremely well-studied Au-25 (SR)(18) cluster both in anionic and cationic form. The relative abundance of the isomeric structures can be controlled by in-source activation. The measured collision cross section of the new isomer agrees extremely well with a recent theoretical prediction (Matus, M. F.; et al. Chem. Commun. 2020, 56, 8087) corresponding to a Au-25(SR)(18)(-) isomer that is energetically close and topologically connected to the known ground-state structure via a simple rotation of the gold core without breaking any Au-S bonds. The results imply that the structural dynamics leading to isomerization of thiolate-protected gold clusters may play an important role in their gas-phase reactions and that isomerization could be controlled by external stimuli.

Automated summary

High-resolution electrospray ionization ion mobility mass spectrometry has identified a gas-phase isomer of the well-studied Au-25(SR)(18) cluster, with relative abundance controlled by in-source activation. The measured properties of the new isomer match theoretical predictions closely, suggesting that structural dynamics play a role in gas-phase reactions of thiolate-protected gold clusters and that isomerization may be manipulated by external stimuli.