Porphyrin Tripod as a Monomeric Building Block for Guest-Induced Reversible Supramolecular Polymerization

Abstract

A porphyrin tripod (DPZnT) connected through a triazole bridge was prepared as a monomeric building block for guest-induced supramolecular polymerization. Although the lone pair electrons in triazolic nitrogen potentially bind to the zinc porphyrin units through axial ligation, the intrinsic steric hindrance suppressed the coordination of the triazole bridge to the porphyrin unit in DPZnT. Therefore, DPZnT formed spherical nanoparticles through pi-pi interactions. The addition of 1,3,5-tri(pyridin-4-yl)benzene (Py3B) caused the guest-induced fibrous supramolecular polymerization of DPZnT by forming a 1:1 host-guest complex, which was further assembled into a fibrous polymer. Furthermore, addition of Cl- to DPZnT induced the transformation of spherical nanoparticles to networked supramolecular polymers. The fibrous and networked supramolecular polymers of DPZnT obtained by adding Py3B or Cl- were depolymerized to their original spherical particles after adding Cu(ClO4)(2) or AgNO3, respectively.