Highly Selective and Sensitive Visual Detection of Fe using a Simple Quinazoline-Based Colorimetric Sensor.

Among the various cations, the Fe ion is one of the most critical transition metal ions in living cells for many cellular functions and enzymatic activities. The decrease or overloading of Fe can lead to different disruptions in humans. Also, Fe, highly toxic, is very common in all industrial wastewater. So, the design and synthesis of Fe chelators as high-selective chemosensors are essential for detecting Fe. In this paper, 6-(6-bromopyridin-2-yl)benzo[4,5]imidazo[1,2-c]quinazoline (BQ) as a novel colorimetric sensor for sensing of Fe was synthesized and characterized by H-NMR, C-NMR, IR, and mass spectrometry. The sensing behavior of BQ toward various cations has been analyzed via colorimetric detection and UV-vis spectroscopy. The BQ was observed to have excellent selectivity and sensitivity to the presence of Fe among the tested ions in aqueous media. Interestingly, the BQ can selectively recognize Fe ions with the naked eye via the color change of colorless to yellow. The effect of pH on the stability and absorption of BQ towards Fe was studied. The results of pH studies showed that the absorbance of complex BQ/Fe remains stable between pH 5-10. Moreover, to determine the sensing behavior of BQ to Fe, the mole ratio method was carried out. The binding stoichiometry of BQ/Fe was assessed by using Job's plot and indicated the 1:1 binding ratio between BQ and Fe. Under the optimal conditions, there was a good linear relationship (correlation coefficient R = 0.9886) in Fe concentration in the 58-114 μM range, with a detection limit of 53.39 nM.