Template-directed syntheses of configurable and reconfigurable molecular switches

Two self-complexing compounds based on donor-acceptor interactions, one comprised of a π-electron-deficient cyclobis(paraquat-p-phenylene) (CBPQT⁴⁺) ring attached to a side-arm component containing π-electron-rich tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP) units, and the other comprised of a CBPQT⁴⁺ ring carrying two side-arms, one containing a TTF unit and the other a DNP unit have been synthesized. ¹H NMR spectroscopy and UV/Vis spectroelectrochemistry have revealed that, while the latter compound behaves as a reconfigurable redox-active molecular switch involving only the side-arm containing the TTF unit in a self-complexing role with the CBPQT⁴⁺ ring (the side-arm containing the DNP unit is essentially a 'spectator'), the former compound behaves as a molecular switch that is reversible and reconfigurable when its starting self-complexing conformation is retained, but becomes only configurable and irreversible when the self-complexing conformation is partially transformed into 'uncomplexed' conformation on oxidation of the TTF unit.