An imidazole ligated zinc(II) transition metal complex as a “turn-off” fluorescent sensor for the selective and sensitive detection of brilliant blue FCF

Abstract

Synthetic colors play a significant role in the food industry and processing sector whereas food safety incidents caused by the illegal addition of colors have gotten more successive. In this study, a highly selective novel zinc incorporated imidazole based metal complex (ZL1) was developed from ligand 2-[(1H-imidazole-2-ylmethylene)-amino]-4-methyl-phenol (L1) in 1:2 (metal:ligand) molar ratio. It was characterized quantitatively using standard spectroscopic techniques. The vital fluorescence properties such as stokes shift, lifetime and quantum yield values were evaluated for the rapid and non-destructive detection of brilliant blue FCF (BB) by the inner filter effect where the emission spectra of ZL1 were overlapped with the absorption spectra of BB. In the presence of BB, a bright yellow colored solution of ZL1 with an emission at 570 nm was quenched with a peak shift observed at 540 nm. It also illustrated the lower detection limit of 2.67 × 10-8 M in the linear range of 1 × 10-6 M to 5 × 10-6 M under optimal conditions. To attain more idea about the properties of a compound, indirect optical band gap energies (Eg) were found using a tauc plot. Encouragingly, the non-toxic property of ZL1 towards myogenic cell line H9c2 was done using a cytotoxicity study and showed excellent photostability. The theoretical approach for geometry optimization, vibrational band assignments, frontier molecular orbitals, and absorption spectrum of the ZL1 were investigated by DFT/B3LYP/6–311 + G(d,p) methods. The theoretical ultraviolet and infrared spectrum of the complex was obtained in vacuum state. Also, the elucidation of the quenching mechanism of fluorescence sensing was proposed with the help of cyclic voltammetry studies. In addition, the practical application of ZL1 was applied to access the BB in food samples showing its potential in food quality control in the future.