Enantioselective Photoinduced Cyclodimerization of a Prochiral Anthracene Derivative Adsorbed on Helical Metal Nanostructures

The generation of molecular chirality in the absence of any molecular chiral inductor is challenging and of fundamental interest for developing a better understanding of homochirality. Here, we show the manipulation of molecular chirality through control of the handedness of helical metal nanostructures (referred to as nanohelices) that are produced by glancing angle deposition onto a substrate that rotates in either a clockwise or counterclockwise direction. A prochiral molecule, 2-anthracenecarboxylic acid, is stereoselectively adsorbed on the metal nanohelices as enantiomorphous anti-head-to-head dimers. The dimers show either Si-Si or Re-Re facial stacking depending on the handedness of the nanohelices, which results in a specific enantiopreference during their photoinduced cyclodimerization: a left-handed nanohelix leads to the formation of (+)-cyclodimers, whereas a right-handed one gives (-)-cyclodimers. Density functional theory calculations, in good agreement with the experimental results, point to the enantioselectivity mainly arising from the selective spatial matching of either Si-Si or Re-Re facial stacking at the helical surface; it may also be influenced by chiroplasmonic effects.