Synthesis of Au38(SCH2CH2Ph)24, Au36(SPh-tBu)24, and Au30(S-tBu)18 Nanomolecules from a Common Precursor Mixture.

ABSTRACT

Phenylethanethiol protected nanomolecules such as Au25, Au38, and Au144 are widely studied by a broad range of scientists in the community, owing primarily to the availability of simple synthetic protocols. However, synthetic methods are not available for other ligands, such as aromatic thiol and bulky ligands, impeding progress. Here we report the facile synthesis of three distinct nanomolecules, Au38(SCH2CH2Ph)24, Au36(SPh-tBu)24, and Au30(S-tBu)18, exclusively, starting from a common Aun(glutathione)m (where n and m are number of gold atoms and glutathiolate ligands) starting material upon reaction with HSCH2CH2Ph, HSPh-tBu, and HStBu, respectively. The systematic synthetic approach involves two steps: (i) synthesis of kinetically controlled Aun(glutathione)m crude nanocluster mixture with 14 gold to thiol molar ratio and (ii) thermochemical treatment of the purified nanocluster mixture with excess thiols to obtain thermodynamically stable nanomolecules. Thermochemical reactions with physicochemically different ligands formed highly monodispersed, exclusively three different core-size nanomolecules, suggesting a ligand induced core-size conversion and structural transformation. The purpose of this work is to make available a facile and simple synthetic method for the preparation of Au38(SCH2CH2Ph)24, Au36(SPh-tBu)24, and Au30(S-tBu)18, to nonspecialists and the broader scientific community. The central idea of simple synthetic method was demonstrated with other ligand systems such as cyclopentanethiol (HSC5H9), cyclohexanethiol(HSC6H11), para-methylbenzenethiol(pMBT), 1-pentanethiol(HSC5H11), 1-hexanethiol(HSC6H13), where Au36(SC5H9)24, Au36(SC6H11)24, Au36(pMBT)24, Au38(SC5H11)24, and Au38(SC6H13)24 were obtained, respectively.