Zwitterionic Cyclophane Molecules: Toward Novel Functional Materials

Abstract For over 60 years, cyclophanes have inspired the design of novel molecular architectures of different sizes and geometries, unleashing significant advances in supramolecular chemistry and also in biomedical and materials sciences. Reported cyclophanes are countless and more complex molecular structures continue to be spawned. Herein, the study classifies cyclophanes into different families to emphasize and feature their structure‐properties relationships. While neutral cyclophanes have attracted more attention owing to their solid‐state physical properties, water‐soluble anionic cyclophanes have been explored predominantly in drug delivery. In the broad family of cationic cyclophanes, viologen‐based cyclophanes ( VBCs ) are widely investigated for designing molecular interlocked molecules (MIMs), molecular switches, and machines owing to their unique electrochemical properties. Despite decades of ground‐breaking research in academia, controlling the cationic cyclophanes and MIMs solid‐state structures is still a limiting factor when it comes to introducing them into functional materials. Here, the study draws attention to some current challenges in cyclophane chemistry from a materials sciences perspective and highlights processes that, if overcome, would lead to cyclophanes producing transformational materials. It is envisioned that zwitterionic VBCs can have a seminal impact on host–guest chemistry, MIMs, molecular machines, and supramolecular tessellations, which can pave the way toward next‐generation technologies.