Dynamics of controlled transformation between two states of coordination-organized supramolecular polymers composed of 1,3-Butadiyne-linked Bis-zinc-porphyrin

Bis(imidazolylporphyrinatozinc) linked with 1,3-butadiyne, BIZnP, can provide two types of supramolecular polymers (extended and stacking, E / S) exclusively by two types of interconvertible imidazole-zinc coordination. Here, a new stimulationresponsive E/S transformation system is developed by adding acetic acid to the kinetically formed E-polymer of BIZnP in the presence of pyridines and an imidazole. By using the method, we investigated the kinetics of E/S-transformation of BIZnP in a vessel and in the microflow channel. As a result, first- and second-order reactions were observed in the E/S transformation. The first one appearing under high-concentration conditions has the rate-limiting step on the dissociation of a long E-polymer. The transformation rate E / S is about 10-20 times faster in the microflow channel than in the vessel. This result is related to the high diffusion rate and shear stresses in the flow method. The dynamics and transformation of the supramolecular structures of BIZnP were visualized by high-speed atomic force microscopy (HS-AFM) on highly ordered pyrolytic graphite (HOPG) in a mixture of 1,1,2,2-tetrachloroethane (TCE) and diethylene glycol dimethyl ether (diglyme). The wide belt-like structure was first observed in TCE, which was assigned as an E-polymer. The initial structure became faint by adding diglyme, and then string-like structures assigned as S-polymers were observed instead. Although both belt-like and string-like structures were moving on the HOPG surface in solution, the HS-AFM method captured the motions. • Controllable system for converting from kinetic to thermodynamic form was developed. • Supramolecular polymer conversion was controlled by the addition of acetic acid. • The conversion time can be adjusted by the type of ligand and concentration. • The conversion time in the flow system was observed to be significantly faster. • The transformation dynamics was visualized using high-speed atomic force microscopy.