8-Hydroxyquinoline based push-pull azo dye: Novel colorimetric chemosensor for anion detection

Abstract

A novel colorimetric chemosensor based on push-pull dye (8HQA) was synthesized and characterized by using IR, 1H/13C NMR and HRMS for the purpose of recognition of anions and cations in DMSO. The absorption maxima of the chemosensor were determined in different solvents. The selectivity and sensitivity of 8HQA to anions were determined with spectrophotometric and 1H NMR titration techniques. The selectivity of 8HQA for studied anions (CN−, F−, Cl−, I−, AcO−, HSO4− and H2PO4−) was determined in DMSO. There is no selectivity between competing anions such as CN−, F− AcO− and H2PO4− at the stoichiometric ratio of 1:1 in UV-vis titrations experiments however, it was observed different color changes upon addition of CN−, F−, AcO− and H2PO4− to the DMSO solution. In addition, the chemosensor showed no colorimetric response for the following anions; Cl−, I− and HSO4− in DMSO. The colorimetric sensing ability of 8HQA was studied in the presence of chloride salts of different cations such as Ca2+, Mg2+, Cu2+, Co2+, Sn2+, Ni2+, Cd2+ and Hg2+. Upon the addition of 4 equiv of each of the cations showed bathochromic shifts except for Ca2+and Cu2+. Interestingly, no selectivity was observed in interaction with metal cations. In addition, the molecular and electronic structures of 8HQA, as well as the molecular complexes of 8HQA, formed with the anions, were obtained theoretically and confirmed by DFT and TD-DFT calculations.