Charge transfer complex based real-time colorimetric chemosensor for rapid recognition of dinitrobenzene and discriminative detection of Fe2+ ions in aqueous media and human hemoglobin

Abstract

A cost-effective and easy to prepare colorimetric aqueous medium dual chemosensor (S1) as a charge transfer complex (CTC) in the form of precipitate was synthesized by one step procedure. S1 showed a highly selective fluorescence quenching response towards 1,3-dinitrobenzene over other nitro explosives with a low detection limit of 0.084 ppb and binding constant of 8.51 × 102 M−1. S1 also showed selective and discriminative detection between Fe2+ and Fe3+ state over other metal ions, which can be noticed in color difference among Fe2+ and Fe3+ by the naked eye. This discriminative detection of two states Fe ion was also found in human deoxyhemoglobin (HHb) and oxyhemoglobin (HbO2) with the binding constant of 132.53 M-1 and 26.46 M−1respectively. Molecular docking between S1 and hemoglobin provides free energy of binding values of –275 kcal mol–1 (HHb) and -253 kcal mol–1 (HbO2), represents that S1 binds with HHb more efficiently than HbO2. The sensing material S1 [(PYRH)+(DNBA)-] was characterized by SC-X-ray study, FTIR, 1H NMR, TG/DTA and Hirshfeld surface analysis. UV–vis spectrophotometry reveals that formation of S1 dependent on the solvent polarity and KCT and εCT with other physical parameters like ECT, ID, RN, ΔG, f and μEN were also calculated using spectrophotometric data. 1:1 stoichiometry of S1 was depicted by the straight-line method and the Benesi-Hildebrand equation. DFT studies provide comparable theoretical data and the HOMO-LUMO energy band gap ΔE=3.515 eV. The N+–H---O- bonding among reactants was found to have an important role in Fe2+ interaction with S1, proving this approach of CTC synthesis as a chemosensor to be novel.