Hydrogen-bonded macrocycle-mediated dimerization for orthogonal supramolecular polymerization

Orthogonal self-assembly represents a useful methodology to construct supramolecular polymers with AA and AB type monomers as commonly used for covalent bond-linked polymers. So far, the design of such monomers has relied heavily on three-dimensional macrocycles and the use of two-dimensional shape-persistent macrocycle for this purpose remains rather rare. Here, we demonstrate a dimerization motif based on a hydrogen-bonded macrocycle that can be effectively applied to form orthogonal supramolecular polymers. The macrocycle-mediated connectivity was confirmed by single crystal X-ray diffraction, which reveals a unique 2:2 binding motif between host and guest bridged by two cationic pyridinum end groups through π-stacking interactions and other cooperative intermolecular forces. Zinc ion-induced coordination with the macrocycle and a terpyridinium derivative enables orthogonal polymerization as revealed by 1H NMR, DLS, and TEM techniques. In addition, viscosity measurements show a transition from oligomers to polymers at the critical polymerization concentration of 17 mM. These polymers are highly concentration dependent. Establishing this new dimerization motif with shape-persistent H-bonded macrocycle widens the scope of options of non-covalent building blocks for supramolecular polymers and augurs well for the future development of functional materials.