Chiral Conflict among Different Helicenes Suppresses Formation of One Enantiomorph in 2D Crystallization

Diastereomeric inter­actions in 2D crystals formed at solid surfaces serve as excellent models for understanding molecular recognition in biomineralization. Adsorption of a penta­helicene racemate on a Au(111) surface leads to 2D conglomerate crystallization, i.e., homo­chiral mirror domains, as observed by scanning tunneling microscopy. Upon mixing 26% of (M)-hepta­helicene into the racemate monolayer, only the (M)-penta­helicene enantio­morph is observed. This effect is explained by a preferred hetero­chiral inter­action between the different helicene species, suppressing the formation of the pure (P)-penta­helicene enantio­morph. These results shine new light onto stereo­selective molecular recognition mediated by van der Waals forces.