Metal Ion Selective Self-Assembly of a Ligand Functionalized Polymer into [1+1] Macrocyclic and Supramolecular Polymer Structures via Metal-Ligand Coordination

Abstract

The design and synthesis of polymer-based metallomacrocycles relying on metal-ligand interactions remain a challenge in the polymer field. Instead of utilizing chemical reactions to synthesize macrocycles, a general approach is proposed to construct metallomacrocyclic structures through supramolecular self-assembly of a specific macroligand with suitable transition metal ions. Therefore, a new ditopic macroligand (L) consisting of PEG end-capped with 2,6-bis(1,2,3-triazol-4-yl)pyridine derivatives is prepared via CuAAC "click" reaction. Four types of metal (Fe²⁺ , Zn²⁺ , Ni²⁺ , and Cu²⁺ ) complexes are obtained by simply mixing a solution of metal ions and L in appropriate concentrations. The investigation of the coordination chemistry suggests that coordination of L with Cu²⁺ results in the formation of a [1+1] metallomacrocycle, while the other metal complexes exclusively lead to the formation of linear metallopolymers and/or larger aggregates. This work provides new insights into designing metallomacrocycles and may have potential application in the synthesis of catenanes and other cyclic or cycle-based topological architectures.

Keywords: [1+1] metallomacrocycle; metal-ligand coordination; supramolecular polymers.