Rationally Designed Supramolecular Organic Hosts for Benzo[a] pyrene Binding and Detection

A series of electronically dissymmetric all-organic macrocycles were synthesized using straightforward synthetic procedures. These macrocycles vary in the nature of the substituents, the geometry of the linkage that connects the electron-deficient aromatic ring, the type of linkage, and the presence or absence of a heteroaromatic ring. These small structural variations impart significant differences in the performance of these macrocycles in binding benzo[a] pyrene, with binding constants up to 2.5 x 10(4) M-1 obtained. They also lead to significant differences in their ability to promote non-covalent energy transfer from benzo[a] pyrene to a BODIPY fluorophore, with energy transfer efficiencies ranging from 32% to 398%. These differences can be explained using a variety of computational investigative techniques, which highlight the flexibility of the macrocycle architectures to accommodate benzo[a] pyrene and to promote close donor-acceptor interactions.