Isolation of ubiquitous Au(40)(SR)(24) clusters from the 8 kDa gold clusters.

We report chromatographic isolation of a new thiolate-protected gold cluster species from the approximately 8 kDa Au(n)(SR)(m) clusters. This new cluster is separated by size-exclusion chromatography from Au(38)(SC(2)H(4)Ph)(24) (a previously reported main component in the approximately 8 kDa gold-thiolate species). Based on detailed MALDI and ESI mass spectrometry analyses, the new cluster possesses a core mass of approximately 8.6 kDa and its formula is determined to be Au(40)(SC(2)H(4)Ph)(24). The Au(40)(SR)(24) species is also found to exist in other thiolate systems, including -SR=SC(6)H(13) and SC(5)H(11), indicating that Au(40)(SR)(24) is a ubiquitous cluster as is Au(38)(SR)(24).