Biphen[n]arene-Based Supramolecular Materials

Abstract

Macrocycles play pivotal roles in supramolecular chemistry and materials science because of their distinctive molecular recognition capabilities and versatile applications in self-assembly. However, traditional macrocycles, such as cyclodextrins, calixarenes, cucurbiturils, and pillararenes, have inherent limitations in terms of cavity size and structural variety, which restrict their ability to encapsulate guest molecules of varying sizes and their potential in constructing multifunctional materials. To address these challenges, our group has developed a simple, universal, and modular strategy for constructing functional macrocycles, termed biphen[n]arenes. This approach leverages structure- or function-oriented modular replacement of reactive, functional, and linking modules. Therefore, biphen[n]arenes with customized cavity size and molecule depth can effectively encapsulate guests from small molecules to biomacromolecules. On the other hand, different from modification of side chains, incorporation of functional primitives into the biphen[n]arene scaffold can leave active sites on both edges to induce additional moieties to improve recognition potency or integrate extra application functionality. These characteristics provide significant advantages in the construction of diverse supramolecular materials.

This Account summarizes the research progress on biphen[n]arene-based supramolecular materials across three major areas: (a) Biomedical materials. By customizing the sizes, shapes, and portal substituents of biphen[n]arenes to match the structural features of biomedical molecules such as drugs, bioactive peptides, and macromolecular biotoxins, we have constructed a series of water-soluble biphen[n]arenes with exceptional recognition capabilities. These biphen[n]arenes demonstrate a range of promising applications, including reversing neuromuscular blockers, combating bacterial infections, delivering peptide agents, detoxifying macromolecular biotoxins, and disassembling fibrous proteins. (b) Luminescent materials. We developed a series of luminescent macrocycles by introducing diverse fluorophores and phosphors onto biphen[n]arene skeletons, which displayed enhanced emission compared to the corresponding monomers. The modular approach provides an efficient and universal strategy for enhancing solid-state emission, termed macrocyclization-induced fluorescence/phosphorescence enhancement. Additionally, structurally diverse luminescent macrocycle cocrystals have been obtained, where solid-state luminescence can be precisely tuned by controlling donor–acceptor stoichiometric ratios and molecular packing modes. (c) Adsorption and separation materials. Biphen[n]arenes and cages exhibit impressive separation capabilities for industrially important mixtures owing to their advanced architectures and diverse supramolecular interactions. These include the separation of cis-/trans-1,2-dichloroethene isomers, benzene/cyclohexane, toluene/methylcyclohexane, cyclohexane/cyclohexene/benzene, cycloheptane/cycloheptene, and tetrahydronaphthalene/naphthalene mixtures. Supramolecular organogels of larger macrocycles, such as terphen[5,6]arenes and quaterphen[5,6]arenes, demonstrate more effective iodine capture in both aqueous and gaseous environments compared to their powder states. After detailing the significant contributions and potential of biphen[n]arenes in creating multifunctional supramolecular materials, this Account also discusses the existing challenges and future directions related to the structures, properties, and applications of biphen[n]arenes. We hope to inspire interdisciplinary researchers and provide new opportunities for the development of advanced functional materials.