Naked-eye colorimetric anion probing and fluorescent switching features of conjugated Schiff Bases derived from 4-(Trifluoromethyl) benzenesulfonamide.

In this work, synthesis, spectroscopic, density functional theory (DFT) and photophysical studies of the three conjugated benzenesulfonamide Schiff bases were reported. We also calculated the energies of the frontier molecular orbitals (FMOs) and UV–Vis spectra of Schiff bases theoretically using the DFT and TD-DFT methods. Additionally, photophysical properties were investigated by UV–Vis and fluorescence spectroscopy techniques. The ground state interactions show that the absorption band has been separated into two branches and bathochromatically tuned to the visible region, and fluorescence intensity decreased in the case of the Schiff base incorporated naphthalene unit. Furthermore, the charge transfer dynamics of the compounds were analyzed using femtosecond transient absorption spectroscopy measurements proving the triplet-triplet transitions via intersystem crossing mechanism. Based on the ultrafast pump-probe experimental results, as well as decay kinetics of the compounds, the Schiff base with naphthalene unit, showed a fast transition to the triplet state (1.2 ps) as compared to Schiff bases including methyl (4 ps) and chloro (2.7 ps) units. However, upon the addition of various anions, the molecule structure gains anion sensing and fluorescence switching capabilities under daylight and UV light. The obtained experimental results pointed out that the modification of Schiff base molecules with methyl, chlorine and naphthalene units affected its photophysical properties as well as excited-state dynamics significantly. [Display omitted] • Novel three conjugated benzene sulfonamide Schiff bases have been synthesized and characterized. • Calorimetrically anion probing features of newly synthesized Schiff bases under daylight and UV light were observed. [ABSTRACT FROM AUTHOR]