An innovative Schiff-base colorimetric chemosensor for the selective detection of Cu²⁺ ions and its applications

A novel Schiff base moiety, (E)-4-(1-hydrazonoethyl)benzene-1,3-diol (2), and 2,4-dihydroxybenzaldehyde were condensed in a 1 : 1 molar ratio to generate 4-((E)-1-(((Z)-2,4dihydroxybenzylidene)hydrazono)ethyl)benzene-1,3-diol (L), which was then characterized using high-resolution mass spectrometry (HRMS), ¹H-NMR, ¹³C NMR, and single-crystal XRD techniques. UV-vis absorbance measurements were used to determine whether the Schiff base could detect the cupric ions more effectively than the other transition metal ions. When Cu²⁺ ions were involved, a new band was observed at 462 nm. From the Job plot, the binding stoichiometry for the anticipated L : Cu²⁺ partnership is determined to be 1 : 1. For the purpose of validating structural correlations and absorption data, DFT simulations were performed. Further, docking studies for L indicated high binding affinity for human hemoglobin, providing vital information about the ligand's favorable binding locations inside hemoglobin binding sites and the consequent interactions with HHb. The binding coefficient and limit of detection were found to be 3.02 × 10⁴ M^-1 and 42.09 nM, respectively. Reversibility of the complex was seen upon the addition of EDTA to the L-Cu²⁺ solution, and a colorimetric variation simulating the "INHIBIT" molecular logic gate was seen upon the addition of Cu²⁺ and EDTA to L. Furthermore, the chemosensor's potential application in the detection of Cu²⁺ in the solid state by chemosensor L also confirms its usefulness in real-world applications emphasizing its versatility and practical utility.