Synthesis and characterization of 4-Halobenzylidene malanonitriles for optical detection of Nickel (II) ions in aqueous solution

In this work, we have developed fluorescent detection techniques for the determination of Ni2+ ions in aqueous medium with sensitivity using metal coordinating fluorescent molecules namely 4-Halobenzylidene malanonitrile. The halogen substituted benzylidene malanonitile were synthesised Knoevenagel condensation reaction of various halogen substituted aromatic aldehydes with malanonitrile and products were characterised by IR and NMR spectroscopy. The obtained benzylidene malanonitiles and are exhibited a fluorescent emission with a peak of 430 nm, 440 nm and 448 nm for chloro, bromo and fluoro substituted compounds, respectively. The intensity of optical emission of the studied molecules is increased proportional to the addition of Ni2+ ions. The effect of different halogen substitution on the fluorescence behaviour of benylidene malononitrile has also been investigated. The synthesised title compounds showed a lowest detection limit of 10-20 M for the Nickel (II) ions in aqueous solution under UV-Vis absorption spectra. The molecule 4- Bromobenzylidene malanonitrile exhibited a lowest detection limit of 10-19 M for the Nickel (II) ions in, aqueous solution, photoluminescence analysis.

Automated summary

In this study, fluorescent detection techniques using metal coordinating fluorescent molecules, namely 4-Halobenzylidene malanonitrile, were developed for sensitive determination of Ni2+ ions in aqueous medium. The synthesized compounds exhibited fluorescent emission with peak wavelengths varying based on the halogen substituent and showed increased optical emission intensity proportional to the addition of Ni2+ ions, with the lowest detection limit being 10-19 M for the Nickel (II) ions in aqueous solution.