Quinoxaline-derived “turn-off” fluorescent sensor for the selective detection of Fe3+: Synthesis, spectroscopic analysis, BSA binding and computational studies

Abstract

A simple quinoxaline-based “turn-off” fluorescent sensor 12-{[1-(4-isopropylphenyl)-1H-1,2,3-triazol-5-yl]methyl}c-12H-benzo[5,6][1,4]thiazino[2,3-b]quinoxaline (BTQT) was synthesised and characterised by various spectroscopic technique including FT-IR, 1D, 2D NMR and mass spectrometry. DFT-based studies have been employed to calculate reactivity descriptor-associated with the molecular structure. UV–visible absorption and fluorescence spectral studies revealed a selective “turn-off” fluorescent response towards Fe3+ with a detection limit of 3.5 µM and a response time of 5 s. Job's plot and mass spectrum establish 1:1 binidng stoichiometry between Fe3+ and BTQT. Spectral studies revealed a static mode of BTQT binding with bovine serum albumin accompanied by hydrogen bonding and weak van der Waals force of interactions. The experimental results of BSA binding were further supported by in silico studies and are in good corroboration with the experimental findings. Such a convenient and simple methodology could impart an auspicious tool for rapid, selective and sensitive analysis of Fe3+ and BSA.