First enantioseparation and circular dichroismspectra of Au38 clusters protected by achiralligands

摘要

Bestowing chirality to metals is central in fields such as heterogeneous catalysis and modernoptics. Although the bulk phase of metals is symmetric, their surfaces can become chiralthrough adsorption of molecules. Interestingly, even achiral molecules can lead to locally chiral,though globally racemic, surfaces. A similar situation can be obtained for metal particles orclusters. Here we report the first separation of the enantiomers of a gold cluster protectedby achiral thiolates, Au38(sCH2CH2 Ph)24, achieved by chiral high-performance liquidchromatography. The chirality of the nanocluster arises from the chiral arrangement of thethiolates on its surface, forming ‘staple motifs’. The enantiomers show mirror-image circulardichroism responses and large anisotropy factors of up to 4×10~(-3). Comparison with reportedcircular dichroism spectra of other Au38 clusters reveals that the influence of the ligand on thechiroptical properties is minor.