Enantioseparation and chiral induction in Ag₂₉ nanoclusters with intrinsic chirality

Abstract

The optical activity of a metal nanocluster (NC) is induced either by an asymmetric arrangement of constituents or by a dissymmetric field of a chiral ligand layer. Herein, we unveil the origin of chirality in Ag 29 NCs, which is attributed to the intrinsically chiral atomic arrangement. The X-ray crystal structure of a Ag 29 (BDT) 12 (TPP) 4 NC (BDT: 1,3-benzenedithiol; TPP: triphenylphosphine) manifested the presence of intrinsic chirality in the outer shell capping the icosahedral achiral Ag 13 core. The enantiomers of the Ag 29 (BDT) 12 (TPP) 4 NC are separated by high-performance liquid chromatography (HPLC) using a chiral column for the first time, showing mirror-image circular dichroism (CD) spectra. The CD spectra are reproduced by time-dependent density functional theory (TDDFT) calculations based on enantiomeric Ag 29 models with achiral 1,3-propanedithiolate ligands. The mechanism of chiral induction in the synthesis of Ag 29 (DHLA) 12 (DHLA: a-dihydrolipoic acid) NCs with a chiral ligand system is further discussed with the aid of DFT calculations. The use of the enantiomeric DHLA ligand preferentially leads to a one-handed atomic arrangement which is more stable than the opposite one, inducing the enantiomeric excess in the population of intrinsically chiral Ag 29 NCs with CD activity.

Chiral Superatomic Nanoclusters Ag47 Induced by the Ligation of Amino Acids

“…The value is lower than most chiral gold nanoclusters, [11,39,55,58,[65][66][67][68][69] but comparable with chiral silver nanoclusters. [56,70] We picked Ag 47 -LVal for the density functional theory (DFT) simulations.T he atomic structure of the cluster was optimized using the GPAW code [71] in the grid mode (grid spacing h = 0.2 )w ith PBE functional [72] and Tkatchenko-Scheffler (TS) Va ndeW aals correction. [73] Thegeometry was considered to be converged when the maximum residual force was below 0.05 eV À1 .A fter optimizing the structure,w e analyzed the electronic structure of the cluster.…”

Surface environment complication makes Ag29 nanoclusters more robust and leads to their unique packing in the supracrystal lattice

“…[9][10][11][12][13] Besides, metal nanoclusters have been served as ideal platforms for the meticulous investigation of structure-property correlations. [14][15][16][17][18][19][20] Consequently, metal nanoclusters are an emerging class of programmable nanomaterials for several promising applications, such as catalysis, drug delivery, energy storage, and biological applications. [21][22][23][24] In the past two decades, silver nanoclusters have received unprecedented attention in the cluster science.…”

“…9–13 Besides, metal nanoclusters have been used as ideal platforms for the meticulous investigation of structure–property correlations. 14–20 Consequently, metal nanoclusters are an emerging class of programmable nanomaterials for several promising applications, such as catalysis, drug delivery, energy storage, and biological applications. 21–24…”

Chiral Superatomic Nanoclusters Ag47 Induced by the Ligation of Amino Acids

“…The maximum anisotropy factor g of Ag 47 is about 1.4×10 −3 at 341 nm for Ag 47 ‐Val and Ag 47 ‐Ile (Supporting Information, Figures S11, S12). The value is lower than most chiral gold nanoclusters, [11, 39, 55, 58, 65–69] but comparable with chiral silver nanoclusters [56, 70] …”