Chirality Induction in the Synthesis of Ag29 Nanoclusters with Asymmetric Structure

Surface ligands play a critical role in the synthesis of metal nanoclusters (NCs) tuning the sizes, compositions, structures, and properties at the atomic level. Chiral ligands often lead to the formation of optically active NCs with directing the handedness of chiral atomic arrangement or providing a dissymmetric field of a chiral ligand layer to the electronic structure. The use of enantiomeric ligand in the synthesis of Ag-29(dithiolate)(12) NCs led to the preferential formation of either right- or left-handed NCs with intrinsic chirality because of the handedness induction ability of chiral ligands. Herein, we investigate the handedness-directing power of a chiral ligand, alpha-dihydrolipoic acid (DHLA), in terms of chirality amplification or suppression phenomena dependent on the temperature and enantiopurity of DHLA in the synthesis of Ag-29(DHLA)(12) NCs. The lowering of temperature in the synthesis of NCs resulted in the suppression of optical activity or handedness excess in Ag NCs because of the substantial involvement of kinetic processes, allowing the formation of NCs with the thermodynamically less favored handedness. The heat treatment allows the metastable NCs to undergo handedness inversion forming the thermodynamically stable NCs. These experimental results suggested that the chiral ligand has a more decisive effect on the thermodynamic stability of NCs rather than on the kinetic process in the formation of NCs.

Automated summary

Surface ligands are crucial in the synthesis of metal nanoclusters, playing a role in tuning the sizes, compositions, structures, and properties. Chiral ligands can induce the formation of optically active nanoclusters and influence the handedness of chiral atomic arrangement. The use of enantiomeric ligand in the synthesis of nanoclusters can lead to the preferential formation of either right- or left-handed nanoclusters with intrinsic chirality.