Ligand effects on the stability of thiol-stabilized gold nanoclusters: Au-25(SR)(18)(-), Au-38(SR)(24), and Au-102(SR)(44)

We have studied the electrochemical and thermodynamic stability of Au-25(SR)(18)(-), Au-38(SR)(24), and Au-102(SR)(44), R = CH3, C6H13, CH2CH2Ph, Ph, PhF, and PhCOOH, in order to examine ligand effects on the stability of thiol-stabilized gold nanoclusters, Au-m(SR)(n). Aliphatic thiols, in general, have higher electrochemical and thermodynamic stability than aromatic thiols, and the -SCH2CH2Ph thiol is particularly appealing because of its high electrochemical and thermodynamic stability. The stabilization of Au-m by nSR for Au-m(SR)(n) can be rationalized by the stabilization of an Au atom by an SR for the simple molecule AuSR, regardless of interligand interaction and system size and shape. Thiol moieties play a strong role in the electron oxidation and reduction of Au-m(SR)(n). Accounting for the characteristics of thiol ligands is essential for understanding the electronic and thermodynamic stability of thiol-stabilized gold nanoclusters.