Three coordination polymers based on 4,4'-bis(2-methylimidazol-1-yl)diphenyl ether: Synthesis, structure and selective fluorescent sensing properties

Abstract

Three CPs [Zn₂(PDA)₂(BMIOPE)₂·3H₂O]_n (1), [Co(Br-BDC)(BMIOPE)]_n (2) and [Co(MIP)(BMIOPE)]_n (3) were synthesized by solvothermal method based on dual-ligand strategy (H₂PDA, Br-H₂BDC, BMIOPE and H₂MIP are 1,3-phenylenediacetic acid, 5-bromo-isophthalic acid, 4,4'-bis(2-methylimidazol-1-yl)diphenyl ether and 5-methylisophthalic acid, respectively). Complexes 1 and 3 exhibit twofold parallel interwoven sql nets. Complex 2 is 2D layer structure. The luminescence property investigations showed that complexes 1-3 could act as multi-responsive fluorescent sensors to detect UO₂²⁺, Cr₂O₇^2- and CrO₄^2- and nitrofurantoin (NFT) through fluorescence turn-off process, presenting excellent sensitivity and selectivity. Finally, the possible fluorescent quenching mechanisms of complexes 1-3 toward the above pollutants are also further investigated by employing spectroscopic methods and quantum chemical calculations. The fluorescence lifetime measurements manifest the mechanism of fluorescence quenching is static quenching process.

Keywords: Coordination polymer; Cr(2)O(7)(2−)/CrO(4)(2−) sensing; Multi-responsive fluorescent sensors; Nitrofurantoin sensing; UO(2)(2+) sensing.