Structural investigation of thiophene thiol adsorption on Au nanoclusters: Influence of back bonds

The adsorption of thiolate radicals on the Au-24 nanocluster truncated from the Au (111) surface is investigated using first principles electronic structure calculations under the density functional theory formalism. Particular emphasis is given to understanding the chemical interactions at the gold-sulfur interface. In order to describe the influence of the back bonds at the thiolate sites we have carried out adsorption studies with thiophene 2-thiolate (-ST) and thiophen-2-yl-methanethiolate (-SCH2T) along with atomic sulfur (S), mercapto (-SH), and methylthiolate (-SCH3). The results suggest that the adsorption geometry at the gold-sulfur interface is strongly dependent on the local environment of the terminal sulfur atom. The interfacial charge transfer is found to be localized along the Au-S bonds and does not influence the molecular structure of the thiophene ring. (C) 2002 American Institute of Physics.