A Schiff base colorimetric sensor for selective and sensitive detection of Cr3+ ions in solution and solid matrix

Trivalent chromium ions are the abundant hazardous metal, which have an impact on plant, animal, human health and water ecosystem. Therefore, an efficient Schiff base colorimetric sensor was developed for the selective detection of Cr3+ ions in an acetonitrile aqueous medium. The structural characterization of synthesized 1,1-hydrazine-1,2-diylidene bis(methanylylidene) bis(4,1-phenylene) bis(azanetriyl) tetrakis (ethane2,1diyl) tetrakis (diethylcarbamodithioate) [HAD] was confirmed using 1H NMR, 13C NMR, FT-IR, and HR-MS. Even in the presence of various metal cations, the probe could instantly detect Cr3+ ions with specific selectivity and high sensitivity and exhibited striking color shifts from colorless to orange, which can be easily observed by the naked eye with a reversible response. The binding mode of HAD towards Cr3+ ions was discovered to be a 1:2 ratio using Job’s plot, HR-MS, which was also supported by density functional theory (DFT) calculations and the binding constant was estimated to be 6.425 ×106 M−1 using the Benesi-Hiledebrand (B-H) plot. The calculated detection limit of HAD to Cr3+ was 4.87 × 10−10 M, significantly lower than World Health Organization (WHO) guidance (0.962 10−6 M). The sensing mechanism of HAD with Cr3+ was investigated by 1H NMR titration, ESI HR-MS and theoretical calculations. A Boolean logical response of molecular AND gate HAD to sense Cr3+ ions was built. Further to improve the practical applicability, solid state HAD and silica supported HAD was prepared and demonstrated for the determination of Cr3+ ions. [Display omitted] •HAD showed rapid absorbance, excellent selectivity and high sensitivity towards Cr3+ ions are summarized.•The detection mechanism is based on Ligand to Metal Charge Transfer (LMCT) upon interaction with Cr3+ ions.•The limit of detection achieved for Cr3+ is 4.87 x 10 -10 M.•The response of HAD toward Cr3+ ion is reversible and reusable.•Solid state HAD and Solid-supported HAD@SiO2 was developed and demonstrated for onsite analysis.