Chiral symmetry breaking yields the I-Au60 perfect golden shell of singular rigidity

S-M Mullins,H-Ch Weissker,J J Pelayo,R Sinha-Roy,I L Garzón,X López-Lozano,R L Whetten

doi:10.1038/s41467-018-05215-3

Abstract

The combination of profound chirality and high symmetry on the nm-scale is unusual and would open exciting avenues, both fundamental and applied. Here we show how the unique electronic structure and bonding of quasi-2D gold makes this possible. We report a chiral symmetry breaking, i.e., the spontaneous formation of a chiral-icosahedral shell (I−Au60) from achiral (Ih) precursor forms, accompanied by a contraction in the Au–Au bonding and hence the radius of this perfect golden sphere, in which all 60 sites are chemically equivalent. This structure, which resembles the most complex of semi-regular (Archimedean) polyhedra (34.5*), may be viewed as an optimal solution to the topological problem: how to close a 60-vertex 2D (triangular) net in 3D. The singular rigidity of the I−Au60 manifests in uniquely discrete structural, vibrational, electronic, and optical signatures, which we report herein as a guide to its experimental detection and ultimately its isolation in material forms.

Highlights

The combination of profound chirality and high symmetry on the nm-scale is unusual and would open exciting avenues, both fundamental and applied
The structure of Au144(SR)[60] (Fig. 1a) comprises four concentric shells of atoms: the Inner Core of two shells of (12) + (30 + 12) sites that have no coordination to ligands; the Grand Core (114 Au atoms) consists of the Inner Core plus 60 Au surface atoms, hereinafter referred to as the Ih−Au60 shell (Fig. 1b), each singly coordinated to thiolates (RS-); the final (4th) shell is conformed by 30 staplemotif units (RS-Au(I)-SR)
The I−Au60 shell structure predicted has not been experimentally characterized so far, and it may appear an unlikely candidate for experimental detection and physical isolation or chemical synthesis, in view of the greater cohesion of filled structures and the presumed reactivity of its exterior surface

Summary

Introduction

The combination of profound chirality and high symmetry on the nm-scale is unusual and would open exciting avenues, both fundamental and applied. We report a chiral symmetry breaking, i.e., the spontaneous formation of a chiral-icosahedral shell (I−Au60) from achiral (Ih) precursor forms, accompanied by a contraction in the Au–Au bonding and the radius of this perfect golden sphere, in which all 60 sites are chemically equivalent. This structure, which resembles the most complex of semi-regular (Archimedean) polyhedra (34.5*), may be viewed as an optimal solution to the topological problem: how to close a 60vertex 2D (triangular) net in 3D. One reason for this neglect is that whereas full Ih-symmetry is manifested by as few as 30, 20, or even 12 equivalent sites (atoms), I-

Methods

Results

Conclusion