Synthesis, structure and nitroaromatic sensing ability of a trinuclear zinc complex with a reduced Schiff base ligand: Assessment of the ability of the ligand to sense zinc ion

Abstract

A trinuclear zinc complex, [Zn{Zn(N3)L}2] {H2L = 2,2′-[(1-ethyl-1,3-propanediyl)bis(iminomethylene)]bis[6-ethoxyphenol]}, has been synthesized and characterized. Its structure has been confirmed by X-ray crystallographic analysis. The complex acts as a sensor for the detection of nitroaromatics in CH3CN solution via turn-off fluorescence response. The solution phase sensing phenomenon has been studied and a strong quenching efficiency has been observed with a quenching constant (KSV) 13.7952 × 102 M−1 for 2-chloro-4-nitrobenzoic acid. H2L displayed high specificity, sensitivity as well as selectivity for zinc ion in its turn-on fluorescence activity. The mechanism of fluorescence enhancement has been proposed, while the metal–ligand binding stoichiometry and binding constant have also been determined. The detection limit of zinc ion is 7.74 × 10−7 M., with the binding constant K = 2.857 × 105 M−1.