Facile Synthesis of Size-Tunable Functional Polyimidazolium Macrocycles through a Photochemical Closing Strategy

A synthetic strategy for the preparation of a series of polyimidazolium macrocycles from the corresponding dicarbene-derived metallacycles is described. Photodimerization of terminal cinnamic esters (UV-irradiation, λ=365 nm) produces the closed metallacycles with perfect stereoselectivity and high yields. Subsequent removal of the template from the photodimerization product results in polyimidazolium macrocycles. The size and shape of the receptor can be tuned easily by changing the length and breadth of the internal bridging groups of the ligands. Preliminary investigation shows the potential of the macrocycle as iodide sensor.