Metal recognition behaviour study of coumarin containing benzimidazole moiety

Abstract

A series of chemical-sensors, benzimidazole-coumarin (M1, M2 & M3), were synthesized and characterized by 1 H NMR, mass spectrometry, and elementary analysis. UV-Vis absorption and emission spectrometer investigated the fluorescent behavior and recognition mechanism of these sensors. The absorption and emission bands of sensor M derivatives were found at 310 to 350 and 390 to 580 nm. The sensor M derivative exhibits a "turn-off " fluorescent quenching and selective complexing capacity towards Cu 2+ ions. The detection limit of sensor M1 is 3.9 nM for Cu 2+ ions, and the coordination ratio was found to be 2:1 ratio by the Job's plot method. The binding constant was also calculated to be Ks 3.41 × 10 9 /M 2 . The fluorescence quenching seen in M-Cu 2+ has been attributed to a lower HOMO-LUMO orbital gap and decreased electron donation from the coordinated imidazolyl coumarin, as found by DFT calculations. The sensor M2 was successfully applied to detect Cu 2+ in the different water samples. A stable complex of sensor M-Cu 2+ was characterized by the Job's plot method, ESI-MS and DFT studies.