The origin of isotope-induced helical-sense bias in supramolecular polymers of benzene-1,3,5-tricarboxamides

The molecular origin of the isotope-induced diastereomeric enrichment in helical supramolecular polymers consisting of trialkylbenzene-1,3,5-tricarboxamides (BTAs) is studied using plane-wave DFT calculations. We demonstrate that the creation of a chiral center at the α-position of the alkyl chains of a BTA by H-D exchange leads to a small but notable preference for the formation of supramolecular hydrogen bonded structures with a particular helicity. The bias for one helical sense preference is caused by the orientation of the vibrational eigenmodes of the C-H and C-D stretching frequencies at the chiral center and by hyperconjugative destabilization of the anti C-H orbital.