Mononuclear Zn(II) Complex Based on N2O Ligand Compartment: First Case to Detect Nitro Explosives

This paper scrutinises the development of low-cost hypersensitive fluorescent probes manipulated chemically with Schiff base complexes and their prospective applicability for the detection of nitro explosives in light of the rapidly expanding demand for anti-trafficking measures. In this study, a new Zn(II) metal complex has been synthesized in one pot using the Schiff base ligand L= 2-methoxy-5-methyl-N-(2-pyridin-2-ylmethylene) aniline. The complex was also thoroughly characterised using various spectroscopic tools and subjected to single crystal XRD analysis. In the asymmetric unit, square pyramidal zinc (II) centre exist in the inner N2O compartment of the ligand L. The intermolecular Cg···Cg interactions exist between two different asymmetric residual units lead to supramolecular assembly along b axis. By turning off the fluorescence response, the complex serves as a sensor for the detection of nitro aromatics in CH₃CN solution. A significant quenching efficiency has been reported with a quenching constant (K_SV) 1.8 × 10⁴ M^-1 for 4-nitrobenzoic acid during investigation of sensing phenomenon in solution phase. In addition, determining the binding stoichiometry of the chemosensor with NO₂ and the binding constant, the mechanism of fluorescence quenching has also been postulated. The detection limit of NO₂ is 7.6×10 ^-7 M, with the binding constant k = 1.1021× 10⁸ M^-1. Additionally, the DFT calculation makes it easier to comprehend the appropriate binding process in light of the findings of experiments. We also designed a paper sensor strip for the visual detection of Nitro Explosive Residues in light of the sensor's potential used in forensic investigations.