A bistable [2]catenane switched by hetero-radical pairing interactions

A bistable [2]catenane composed of a tetracationic cyclophane, namely cyclobis(paraquat-p-phenylene) (CBPQT4+) that is mechanically interlocked by a neutral macrocylic component containing both a 1,5-dioxynaphthalene (DNP) and a naphthalene-1,4,5,8-bis(dicarboximide) (NDI) unit, was obtained by using template-directed synthesis via click chemistry. In the fully oxidized state, the CBPQT4+ component encircles the DNP unit, driven by donor-acceptor interactions. Upon reduction of both the CBPQT4+ ring and the NDI unit, the CBPQT2(˙+) ring undergoes shuttling and resides on the NDI˙- station, driven by coulombic-enhanced spin-pairing interactions between different aromatic radicals.