Spectroscopic, colorimetric and theoretical investigation of Salicylidene hydrazine based reduced Schiff base and its application towards biologically important anions

A reduced Schiff base anionic receptor 1 [N,N′-bis-(2-hydroxy-5-nitro-benzyl)hydrazine] has been synthesized, characterized and reported as a selective chromogenic receptor for fluoride, acetate and phosphate anions over the other tested anions such as chloride, bromide, iodide and hydrogensulphite. Colorimetric naked-eye detection and UV–vis absorption spectroscopic techniques were used to distinguish the recognition behaviours towards various anions. The receptor–anion complexation mainly occurs via hydrogen bonding interactions which facile to generate the charge transfer band in the UV–vis spectra and cause large bathochromic shift as well as naked-eye colour change. Complexation stoichiometry, binding constant and free energy change due to complex formation were determined from Benesi–Hildebrand plot. The binding constant and the free energy change values are well interactive for spontaneous complexation. The experimental results have been correlated with the theoretical calculations using B3LYP hybrid functional and 6-311++G(d,p) basis set for both the receptor and complex by Density Functional Theory (DFT) method.

A reduced Schiff base N,N′-bis-(2-hydroxy-5-nitro-benzyl)hydrazine has been synthesized, characterized and reported as a chromogenic receptor for multi-anions detection. The receptor–anions complexation occurs via hydrogen bonding interactions which facile to generate the charge transfer band in UV–vis spectra and cause large bathochromic shift as well as naked-eye colour change. Complexation stoichiometry, binding constant and free energy change have been reported using Benesi–Hildebrand plot. The experimental results have been correlated well with theoretical Density Functional Theory (DFT) calculation.Figure optionsDownload as PowerPoint slideHighlights
► Applications of reduced Schiff base receptor towards multi-anions detection.
► Synthesis and characterization of N,N′-bis-(2-hydroxy-5-nitro-benzyl)hydrazine.
► Multi-anions detection based on spectroscopic techniques and naked-eye colour change.
► Spectroscopic and molecular modelling study of reduced Schiff base–anion complexes.