Derivatives of the thiolate-protected gold cluster Au25(SR)18-1
Department of Physics and Department of Chemistry, Nanoscience
Center, University of Jyväskylä, 40014
a e-mail: email@example.com
Received in final form: 21 December 2010
Published online: 27 April 2011
Loss of small fragments (like AuL, Au2L3, Au4L4) have been found systematically in several MALDI and FAB experiments on thiolate-protected gold clusters of different sizes. When using the cluster Au25L18-1 as parent cluster, the fragmented cluster Au21L14-1 has been reported to be obtained in high proportion (L = SCH2CH2Ph). Here we analyse a few possible fragmentation patterns of the well-known parent cluster Au25L18-1 (L = SCH3). Using DFT calculations we study the different atomic configurations obtained after a AuL fragment is lost from Au25L18-1. We found energetically favourable configurations that can be written as Au13 [Au2L3]6-z[AuL2]z-1, where the modification can be described as a replacement of the long protecting unit by a short one (Au2L3 → AuL2). A full replacement (z = 6) gives rise to a protected Au19L12-1 cluster. This mechanism does not modify the super-atomic electronic structure of the gold core, i.e., all these fragments remain an 8 electron super-atom clusters exactly like the parent Au25L18-1. We suggest that the Au19L12-1 cluster could be realized by using a bulky thiolate, such as the tert-butyl thiolate SC(CH3)3 .
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag 2011