Synthesis of Mono‐, Di‐, Tri‐, and Tetra‐cationic Pyridinium and Vinylpyridinium Modified [2.2]Paracyclophanes: Modular Receptors for Supramolecular Systems.

In this report, a new series of mono‐, di‐, tri‐, and tetra‐cationic pyridinium and vinyl pyridinium‐modified [2.2]paracyclophanes as useful molecular tectons for supramolecular systems are described. Regioselective functionalization at specific positions, followed by resolution step and successive transformations through Pd‐catalyzed Suzuki‐Miyaura and Mizoroki‐Heck cross‐coupling chemistry furnish a series of modular PCP scaffolds. In our proof‐of‐concept study, on N‐methylation, the PCPs bearing (cationic) pyridyl functionalities were demonstrated as useful molecular receptors in host‐guest supramolecular assays. The PCPs on grafting with light‐responsive azobenzene (−N=N−) functional core as side‐groups impart photosensitivity that can be remotely transformed on irradiation, offering photo‐controlled smart molecular functions. Furthermore, the symmetrical PCPs bearing bi‐, and tetra‐pyridyl functionalities at the peripheries have enormous potential to serve as ditopic and tetratopic 3D molecular tectons for engineering non‐covalent supramolecular assemblies with new structural and functional attributes. [ABSTRACT FROM AUTHOR]