Double-cavity cucurbiturils: synthesis, structures, properties, and applications.

Double-cavity Q[ n ]s are relatively new members of the Q[ n ] family and have garnered significant interest due to their distinctive structures and novel properties. While they incorporate n glycoluril units, akin to their single-cavity counterparts, their geometry can best be described as resembling a figure-of-eight or a handcuff, distinguishing them from single-cavity Q[ n ]s. Despite retaining the core molecular recognition traits of single-cavity Q[ n ]s, these double-cavity variants introduce fascinating new attributes rooted in their distinct configurations. This overview delves into the synthesis, structural attributes, properties, and intriguing applications of double-cavity Q[ n ]s. Some of the applications explored include their role in supramolecular polymers, molecular machinery, supra-amphiphiles, sensors, artificial light-harvesting systems, and adsorptive separation materials. Upon concluding this review, we discuss potential challenges and avenues for future development and offer valuable insights for other scholars working in this area with the aim of stimulating further exploration and interest.