Water-Soluble Chiral Ag₂₉ Clusters Protected by Monothiol N-Acetyl-(S)-penicillamine Synthesized in One Pot

Abstract

Despite significant advances in atomically precise Au clusters with chirality, Ag clusters with the relevant features are still less explored. In this study, we report successful synthesis of chiral Ag₂₉ clusters protected by water-soluble monothiol in one pot, which is carried out by reducing Ag ions in the presence of N-acetyl-(S)-penicillamine (S-NAP) and triphenylphosphine (TPP) at 10 °C, yielding the Ag₂₉(S-NAP)₂₄ cluster. The obtained cluster is isolable as a solid-state powder. Optical absorption of Ag₂₉(S-NAP)₂₄ is almost identical with that of Ag₂₉(R-DHLA)₁₂, where DHLA denotes α-dihydrolipoic acid, and magnetic circular dichroism (MCD) results support the similarity of their electronic structures. The anisotropy factor of Ag₂₉(S-NAP)₂₄ is comparable to or larger than that of Ag₂₉(R-DHLA)₁₂, suggesting that the surface shell structure of Ag₂₉(S-NAP)₂₄ is inherently chiral, as has been observed for Ag₂₉(R-DHLA)₁₂. Then the use of enantiopure NAP would preferentially lead to a one-handed atomic arrangement in the clusters.