Spectroscopy and a theoretical study of colorimetric sensing of fluoride ions by salicylidene based Schiff base derivatives

Three colorimetric anion sensors based on salicylidene Schiff bases (salicylaldehyde-o-aminophenol [SA1 ], 3,5-dimethyl-salicylaldehyde-o-aminophenol [SA2], and 3,5-dichloro-salicylaldehyde-o-aminophenol [SA3] were comprehensively studied based on experimental methods combined with theoretical calculations. All derivatives showed high sensitivity for colorimetric detection of fluoride ions (F-) with a binding stoichiometry of 1:1 in acetonitrile solutions. The color of the sensor solutions visibly changed from light yellow to orange red in the presence of F-. From the experimental results, SA1 and SA2 showed higher potential as F- sensors than SA3 due to their higher selectivity with a limit of detection (LOD) as low as 8 x 10(-5), 21 x 10(-5) and 7 x 10(-5) M, respectively. The optimized structure and electronic transitions were confirmed by DFT and TDDFT studies. In this study, F- detection mechanism is proposed based on experimental and the density functional theory (DFT) calculation. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Three colorimetric anion sensors based on salicylidene Schiff bases were comprehensively studied for the detection of fluoride ions, with experimental methods and theoretical calculations revealing differences in performance and detection mechanisms.