Fluorescence chemosensor for anion recognition, solvatochromism and protein binding studies based on Schiff- base derivative

Abstract

A new salicylidene-based chemosensor (E)-N1-(2-hydroxy-3-methoxy-5-nitrobenzylidene)-N2-phenylbenzene-1,2-diamine (MNP) has been developed by condensation of 3-methoxy-5-nitrosalicylaldehyde with N-phenyl-o-phenylenediamine and analysed using FT-IR, 1H-NMR and ESI-MS spectral techniques. The photophysical properties of MNP, including solvatochromism were investigated and the colour changed from bright yellow to red in the presence of water. This MNP specifically detects only Cu2+ with "turn-off" and a colour turned from light yellow to violet in CH3CN/H2O (9/1, v/v) mixture.The optimized geometry of the MNP-Cu complex was analyzed using DFT methods and the results is confirm the formation of the MNP-Cu complex. Besides, the F− and H2PO4−anions are preferentially sensed by the MNP in comparison to other anions, leading a "turn-off" and the colour change from light yellow to dark yellow in the THF medium. From the pH sensor data, the fluorescence intensity increased at pH 4.0 due to protonation of the -OH group. The interaction of the MNP with protein molecules (BSA, HSA) was investigated using absorption and emission spectral methods. The investigation computed values of the binding constant and the Stern-Volmer quenching constant demonstrated that the MNP had a far stronger affinity for BSA than for HSA. The interaction of the MNP with protein molecules was confirmed using docking studies.