Modular Scaffolds for Supramolecular Systems: In this report, a new series of mono-, di-, tri-, and tetra-cationic pyridinium and vinylpyridinium modified [2.2]paracyclophanes (PCPs) is described. On N-methylation, the 3D PCPs bearing (cationic) pyridyl and vinylpyridinium functionalities have been demonstrated as efficient molecular receptors for application in supramolecular systems. 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.

Abstract

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.