Tuning the sensing properties of isophthalic dihydrazide-based receptor via formation of organic–inorganic hybrid and metal complex: An enhanced sensing activity for Hg2+ and CN− detection in semi-aqueous medium

Abstract

A Schiff base receptor H2L has been synthesized through a condensation reaction between 2-hydroxy-3-methoxybenzaldehyde and isophthalic dihydrazide. The compound has been characterized by various characterization techniques such as 1H, FT-IR, CHNS and single crystal X-ray crystallography. Despite its limited solubility in water, a strategy was employed to enhance its effectiveness in aqueous environment by forming fluorescent nanoaggregates of H2L through a re-precipitation method. The fluorescent nanoaggregates of H2L show strong recognition ability towards Hg2+ ions through a fluorescence turn-on mechanism in H2O–DMSO (90 %, v/v). The study has been extended by developing a hybrid nano-assembly of H2L as Ag@H2L which exhibits higher sensitivity for Hg2+ ions with an improved detection limit 9.3 × 10−9 M as compared to that of organic nanoaggregates having 7.9 × 10−8 M in H2O–DMSO (90 %, v/v). Further Hg2+ complex of H2L has also been synthesized and characterized using elemental analysis, mass spectrometry and IR, UV–Vis spectroscopic techniques. The findings have been complimented by density functional theory (DFT) computations. The synthesized H2L-Hg complex is able to detect CN− ion using UV–Vis spectroscopy in H2O–DMSO (80 %, v/v) with a detection limits of 1.04 × 10−6 M.