Uv-Vis Spectroscopic and Colorimetric Anion Detection and Fluorescence "On-Off" Properties of New 3-Amino-4-Hydroxybenzenesulfonic Acid-Based Imines Depending on the Strength and Position of the Electron Donor Substitution

Abstract

We synthesized new imine compounds ( 1 - 3 ) by reacting 3-amino-4-hydroxybenzenesulfonic acid with 2,5-dihydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde and 2-hydroxy-3-methoxybenzaldehyde. The structure of the synthesized compounds was elucidated from elemental analysis, 1H- and 13C-NMR, FTIR and UV-Vis spectra data. The anion sensor properties of the compounds were investigated both UV-Vis spectroscopically and calorimetrically under sunlight and UV light. A theoretical analysis of their structures was also conducted using density functional theory. A variety of biological properties of these compounds were also investigated, including their antimicrobial activity, DNA binding, and DNA cleavage properties. Again, we measured antioxidant activity using the DPPH method. On the other part, the fluorescence measurements were conducted to analyze steady-state interactions and it was concluded that the emission signal was significantly affected by the position and strength of the electron-donating moiety. According to the results of femtosecond absorption spectroscopy experiments, the quenching of the fluorescence signal can be ascribed to intersystem crossing (ISC) and intramolecular charge transfer mechanisms depending on the position of the hydroxy and the presence of the methoxy moieties, respectively. This research provides a new design strategy for the biological activity, anion sensor and optical properties of 3-amino-4-hydroxybenzenesulfonic acid-based Schiff bases.

Keywords: Biological activity, 3-Amino-4-hydroxybenzenesulfonic acid, Femtosecond transient absorption spectroscopy, Anion sensor, DPPH method, Density Functional Theory (DFT)