Supramolecular polymers based on molecular recognition of bisporphyrin clefts

This review highlights supramolecular polymers based on bisporphyrin clefts, which are rigidly linked porphyrin dimers that function as electron-rich molecular tweezers and incorporate three addressable recognition modes: donor-acceptor host-guest complexation, self-complementary dimerization, and metal coordination. These interactions can induce supramolecular polymerization and enable interchange among supramolecular polymer-chain structures, affording attractive functions in solution and in the bulk. This feature article first discusses head-to-tail host-guest complexation-directed step-growth polymerization and ring-chain equilibria of heterotopic monomers bearing both a cleft and an electron-deficient guest, as well as redox regulation of supramolecular polymer chains through redox-tuning of donor-acceptor host-guest complexation. It also describes polymerization driven by self-complementary dimerization, post-polymerization main-chain editing via recognition-pair exchange, and helicity control using built-in or external chirality, affording amplified chiroptical readouts of solvent chirality. Finally, cooperative coupling of host-guest interactions and coordination cross-linking is highlighted as a pathway from supramolecular polymer chains to supramolecular polymer networks, yielding gels and robust free-standing films.