Enantioselective sensing driven by the interplay of point, helical and planar chirality in pillar[5]arene...

Chirality plays a central role in molecular recognition, and systems combining multiple, interdependent chiral elements can offer enhanced enantioselectivity. Here we show that covalent tethering of a dihydroxy-pillar[5]arene with meso-2,11-dibromododecanedioate yields diastereomeric pseudo[1]catenanes that combine three stereogenic features: two point chiral centers within the aliphatic linker, a helical chirality (P/M) induced by macrocycle closure, and a planar chirality of the pillararene ring. This system exhibits dynamic stereochemical behaviour involving in/out conformational equilibria, accompanied by inversion of the planar chirality. Using NMR spectroscopy, X-ray diffraction, DFT calculations and circular dichroism, we characterize the structures and dynamics of these macrobicyclic pillararenes, including guest-induced inclusion-exclusion processes. Hydrolysis affords a dicarboxyl-functionalized receptor capable of recognizing diamines via host-to-guest proton transfer, while enantiopure derivatives act as chiroptical sensors able to discriminate between L- and D-lysine esters. These results demonstrate how coupling multiple types of chirality can be exploited for responsive molecular recognition.