Chiral Superatomic Nanoclusters Ag47 Induced by the Ligation of Amino Acids

Silver nanoclusters containing Ag-0 atoms protected by amino acids were synthesized and characterized. Chiral superatomic silver nanoclusters [Ag47L12(C equivalent to(CBu)-Bu-t)(16)]BF4 (L=l-/d-valine or l-/d-isoleucine) have been prepared by reducing AgC equivalent to(CBu)-Bu-t and amino acids (AAs) with NaBH4. Single crystal X-ray diffraction revealed that these clusters have T symmetry, and the Ag-47 metal kernel can be viewed as a tetracapped truncated tetrahedron (Ag-17) surrounded with six W-shaped Ag-5 units. The clusters are homochiral as evidenced by CD measurements. As for the strong CD signals, large contributions are found from the occupied Ag s,p states (superatomic D states) near the Fermi level. Electron counting revealed that these clusters are 18-electron systems, suggesting they are superatomic clusters. The superatomic nature with a 1S(2)1P(6)1D(10) configuration was supported by DFT calculations. This work paves the way of taking AAs as facile chiral induction agents for the synthesis of metal nanoclusters.

Automated summary

Silver nanoclusters protected by amino acids were synthesized and characterized in this study. Chiral superatomic silver nanoclusters with T symmetry were prepared, showing homochirality as evidenced by CD measurements. The CD signals were mainly contributed by the Ag s,p states near the Fermi level.