Copper-based electrochemical sensor derived from halogen-substituted Schiff base for selective detection of neurotransmitter dopamine: Insight from DFT and docking analysis

Abstract

The significant influence of dopamine levels on biological processes and diseases necessitates precise and selective detection methods, crucial for conditions like Parkinson's and Alzheimer's diseases. In this study, copper(II) complexes (C1-C3) derived from halogen-substituted Schiff base ligands were synthesized in situ without isolating the ligands, employing methanol as a solvent at room temperature. Characterization through FTIR, UV–Vis, elemental analysis, and mass spectroscopy, along with single crystal X-ray diffraction (SCXRD) analysis, unveiled the solid-state structures of the complexes. Notably, the ligands acted as bidentate mono-negative, coordinating the Cu(II) ion through oxygen and nitrogen atoms, resulting in a square planar geometry. These modified complexes were applied to glassy carbon electrodes (GCEs) for electrochemical sensing of dopamine using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) methods, with dopamine concentrations ranging from 2 to 10 μM. While C2 did not detect dopamine at any tested concentrations, C1 and C3 emerged as effective electrode materials for dopamine sensing, with C3 exhibiting superior performance by providing an effective surface area for the electrochemical oxidation of dopamine. The sensitivity and limits of detection (LOD) for C1 and C3 were determined to be 0.72 μAcm⁻² μM⁻¹ and 1.67 μM, and 3.72 μAcm⁻² μM⁻¹ and 0.52 μM, respectively. The proposed method exhibited no interference by γ-amino butyric acid, uric acid, ascorbic acid, and glucose at concentrations of 15 μM. Additionally, results from computational studies involving DFT, molecular docking, and molecular dynamic simulations not only supported the experimental findings but also elucidated the interaction mechanisms between the compounds and dopamine. These findings position the electrochemical sensors, particularly C3, as promising candidates for the development of sensitive and low-limit electrochemical sensors.