The Colorimetric Signaling of Water Content by a Deprotonated Schiff Base in some Aprotic Organic Solvents

Abstract

A simple Schiff base, (E)-2-[1-{2-(2,4-dinitrophenyl)hydrazono} ethyl]phenol (Hdph) and its deprotonated form, (E)-1-(2,4dinitrophenyl)-2-{1-(2-hydroxyphenyl)ethylidene} hydrazine-1ide (dph) have been synthesized and characterized by various physicochemical and spectroscopic techniques. Their structures have also been determined by single-crystal X-ray crystallography. The dph has been utilized as a colorimetric probe for the signaling of water content in some water-miscible aprotic organic solvents (acetonitrile and tetrahydrofuran). The dph reveals a pronounced colorimetric behavior in response to the variation of water content in these solvents. Significant changes in UV-visible absorption spectra permit a ratiometric analysis of the signaling behavior. The spectral changes are pronounced for the water content of less than 10 %, which is suitable for the application of dph as a receptor for the determination of water content in binary aqueous organic solvents having lower water content. The limit of detection (LOD) for water content in acetonitrile and tetrahydrofuran is calculated as 0.20 % and 0.28 %, respectively.