Schiff base as a fluorescent sensor derived from chromone moiety for the effective detection of Zn (II) ions

A new Schiff base 5-[(4-Oxo-4H-chromen-3-ylmethylene)-amino]-1H-pyrimidine-2, 4‑dione (CUR) was synthesized from chromone moiety and identified as a colorimetric as well as a fluorescent probe for Zn2+ ions detection. Characterization of CUR was done by utilizing 1H NMR, 13C NMR, FTIR, and HRMS analytical techniques. UV–Vis absorption and fluorescence studies revealed that this probe CUR offered great selectivity and sensitivity towards Zn2+ ions above other added metal ions, namely; Cd2+, Hg2+, Ag+, Zr2+, Cr3+, Cu2+, Mn2+, Fe3+, Ni2+, Co2+, Al3+, and Pb2+. A 2:1 binding stoichiometry among CUR and Zn2+ ions was obtained using Job's plot analysis and further confirmed by 1H NMR titrations, and HRMS parameters. The binding constant (Ka) and limit of detection (LOD) for Zn2+ ions were measured to be 7.7 × 106 M−1 and 9.6 × 10−9 M, respectively, using fluorimetric titrations with the help of the Benesi-Hildebrand equation (B-H equation). DFT computational studies also validated the results obtained from absorption and emission studies. The pH and time response studies ensured the stability of CUR and additionally, it was effectively implemented to quantify Zn2+ ions in the collected real water samples.