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

Abstract

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.

Supramolecular Luminescent Sensors

“…Work in the Levine group has included the design and synthesis of aromatic ring-containing macrocycles, which have demonstrated enhanced binding affinities for aromatic guests compared to nonaromatic cyclodextrin hosts, and more efficient energy transfer between an aromatic analyte and high quantum yield aromatic fluorophore when both are bound in the macrocycle’s interior . Much of this enhanced performance is attributed to favorable π–π stacking interactions, and computational modeling of the complexes supports favorable and close-range interactions between the aromatic rings in the various system components …”

“…Higher-order BODIPY architectures, including dimers, trimers, and polymers, have been reported, and many BODIPY constructs maintain high quantum yields even in the solid state . As a result of their favorable properties, BODIPY fluorophores have been used in a number of luminescent sensing schemes, including as high quantum yield energy acceptors from aromatic toxicant donors, , as part of white light-emitting constructs, , and as transducing elements for the detection of phosgene, mercury and copper cations, and many other analytes. − …”

“…The macrocyclic hosts discussed in this section are those that do not fall into any of the previously discussed categories. While the classes of macrocycles previously discussed have demonstrated favorable performance as supramolecular luminescent sensors, designing new classes of macrocycles has notable advantages, including the ability to manipulate the intermolecular forces that govern host–guest interactions, leading to the creation of hosts that are highly suited to bind specific targets . For example, highly conjugated tetracationic cyclophane ExBox was designed by Stoddart to form strong inclusion complexes with PAHs based on π–π stacking and electrostatic (cation-π) interactions .…”

“…For example, highly conjugated tetracationic cyclophane ExBox was designed by Stoddart to form strong inclusion complexes with PAHs based on π–π stacking and electrostatic (cation-π) interactions . Additionally, the Levine group has designed a series of macrocycles bearing electron-rich and electron-deficient aromatic units, which they used to elucidate the effect that small changes in host structure and configuration have on the ability to bind small molecule guests …”

Sessler Early Career Researcher Prize: M. Levine / International Award, Society of Polymer Science, Japan: A. D. Schlüter / The Chemical Record Lectureship: K. Maruoka

“…Levine and her group are interested in the use of cyclodextrin‐based supramolecular systems to solve problems in the areas of sensor development and molecular recognition. She has reported in the European Journal of Organic Chemistry on supramolecular hosts for benzo[ a ]pyrene binding and detection, and on β‐cyclodextrin dimers for squaraine binding …”