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

Abstract

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.