Investigation about the complexation of trimethylammonium-derived pillar[5]arene with indole and azaindole derivatives

Abstract

Indoles and azaindoles are very interesting heterocycles found in naturally occurring and synthetic molecules exhibiting several biological activities associated with its physicochemical properties. Here, we report a study about the inclusion complex formation between trimethylammonium-derived pillar[5]arene (P5A) with indole and azaindole derivatives by NMR and molecular dynamics simulations. Our results indicate that indole forms the most stable inclusion complex of the hosts, with its benzene fragment incorporated near to the centre of the cavity. On the other hand, 5-azaindole presents a weaker interaction with P5A, orienting preferentially the pyrrole moiety toward the host cavity. 7-Azaindole switches between two conformations with the pyridine fragment incorporated inside the cavity. Based on these results, we believe these preliminary study of how the guest structure modifies the structure of the inclusion complexes, and the molecular recognition can be further used in the preparation of new functional supramolecular systems including drug delivery systems.