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 × 10⁴ 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. A series of 10 organic macrocycles were designed, synthesized, and evaluated for their ability to bind benzo[a]pyrene and facilitate benzo[a]pyrene to BODIPY energy transfer. These results highlight the relationship between structural features of hosts, their overall conformations, and their ability to participate in intermolecular interactions and supramolecular applications.