Pyridine-based tricarboxamides: complementary monomers for supramolecular copolymerization with C3-symmetric oligophenylenetricarboxamides

Abstract

The supramolecular copolymerization of triangular-shaped oligophenylenetricarboxamides 1 with the electronically and geometrically complementary pyridine tricarboxamides 2 is investigated. Moreover, amplification of asymmetry between both tricarboxamides is also studied both experimentally and by making use of mathematical models. In the modified seargents and soldiers (mSaS) experiments between achiral tricarboxamide a-1 and chiral Py-based (S)-2 or (R)-2, the existence of amplification of asymmetry is proved. In these experiments, the point chirality embedded in the side chains of (S)-2 or (R)-2 yields homochiral copolymers upon mixing with achiral a-1. The formation of the heteropolymers poly-(S)-1-co-(R)-2 or poly-(R)-1-co-(S)-2 is also studied by mixing the monomeric species with opposite point chirality [(S)-1 + (R)-2 or (R)-1 + (S)-2] in different ratios but keeping the total concentration constant. These experiments reveal a weak amplification of asymmetry that could be indicative of an inefficient supramolecular copolymerization of both chiral species. However, the application of the copolymerization model shows that these geometrically and electronically complementary species form copolymers with a block microstructure, in which large blocks of homopolymers poly-1 and poly-2 coexist with a very low number of heterocontacts. This arrangement of the blocks of opposite helicity finally results in the experimentally observed weak amplification of asymmetry.