Formation of Supramolecular Polymers from Porphyrin Tripods

Abstract

A porphyrin tripod (PZnT) composed of three zinc porphyrin wings connected via triazole bridges was prepared as a monomeric building block for a supramolecular polymer. PZnT formed long fibrous supramolecular polymers with a diameter of 7 nm through the axial coordination of triazole nitrogen atoms to zinc porphyrins. The molecular packing structure of a PZnT-based supramolecular polymer was assigned as a hexagonal columnar phase. PZnT formed a stable 1:1 host-guest complex with 1,3,5-tris(4-pyridyl)benzene (Py3B) through axial coordination of pyridyl groups to zinc porphyrins. The host-guest complex between PZnT and Py3B adopts a cone-shaped geometry. After the addition of Py3B, the host-guest complex exhibited a characteristic X-ray diffraction pattern of rectangular columnar ordering. Furthermore, the formation of supercoiled helical fibrous assemblies was observed by transmission electron microscopy (TEM).