Schiff bases as analytical tools: synthesis, chemo-sensor, and computational studies of 2-aminophenol Schiff bases?

Materials Advances Pub Date: 2023-05-02 DOI: 10.1039/D3MA00097D

Abstract

Schiff bases of 2-((2-hydroxybenzylidene)amino)phenol (MJ1) and 4-bromo-2-(((2-hydroxyphenyl)imino)methyl)phenol (MJ2) were synthesized from 2-aminophenol and screened for the detection of some biologically important metal ions. UV-vis spectroscopy screening, electrochemical studies, and theoretical calculations of the ligands (MJ1 and MJ2) revealed the sensing properties of the probes. The binding interactions of probes MJ1 and MJ2 with Cu2+, Zn2+, and Ni2+ resulted in redshifts in the absorption maxima. MJ1 exhibited reversibility of its metal complexes with Cu2+ and Zn2+ in an EDTA solution. The electrochemical behavior of both probes with Cu2+, Zn2+, Ni2+, Cr3+ resembled voltammograms with one or two quasi-reversible redox processes, indicating complex formation between the probes and metal ions. The electrochemical screening showed none or insignificant binding interactions between the probes with Cr3+. The change in electro-activeness of ligands MJ1 and MJ2 upon complexation with metal ions (Cu2+, Zn2+, and Ni2+) suggested a metal-to-ligand charge transfer (MLCT) and intramolecular charge transfer binding mechanism. The complex formed between the sensor and ligand was determined using density functional theory employing the B3LYP functional and the LANL2DZ and 6-311+G(d,p) basis sets. Atomic charge and molecular orbital analyses of the frontier molecular orbitals also support the MLCT mechanism. The global reactivity descriptor parameters show that MJ2 may be a better electron acceptor than MJ1.

Graphical abstract: Schiff bases as analytical tools: synthesis, chemo-sensor, and computational studies of 2-aminophenol Schiff bases
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