Origin of magic stability of thiolated gold clusters:: A case study on Au25(SC6H13)18

The present work aims to test the validity of the electronic shell model for Au-25(SC6H13)(18) by monitoring the charge state of the Au: S core and thereby to elucidate the origin of magic stability. Electrospray ionization mass spectrometry revealed that the Schiffrin method yields [Au-25(SC6H13)(18)](x) with a distribution of charge states, which shifts toward negative values with reduction time. The stable ions [Au-25(SC6H13)(18)](1+) and [Au-25(SC6H13)(18)](1-) can be synthesized by chemical oxidation and reduction of [Au-25(SC6H13)(18)](0), respectively. These findings lead us to conclude that electronic shell closing is not a crucial factor for the high stability of [Au-25 (SC6H13)(18)](x) (X = 1-, 0, 1+). We ascribe magic stability to the core-in-cage structure predicted theoretically.