EFFECT OF Cu(II) COORDINATION ON THE REDOX BEHAVIOUR OF CURCUMINOIDS: A CYCLIC VOLTAMMETRIC INVESTIGATION
The electrochemical behaviour of a series of curcuminoids and their Cu(II) complexes was investigated using cyclicvoltammetry to evaluate the influence of metal coordination and substituent effects on electron-transfer characteristics. Cyclic voltammetric measurements were carried out in a methanolic mediumcontainingtetrabutylammonium iodide as the supporting electrolyte using a glassy carbon electrode at different scan rates. Thefree curcuminoid ligands exhibited a single, well-defined reversible redox couple in the positive potential regionwith ΔEp values ranging from 0.05–0.07 V and Ipa/Ipc ratios close to unity, indicating diffusion-controlled reversibleelectron transfer. Upon coordination with Cu(II), noticeable changes in the redox potentials were observed, indicating modification of the electronic environment through metal–ligand charge delocalisation. In addition totheligand-centered process, the Cu(II) complexes displayed an extra redox couple assigned to the Cu(II)/Cu(I) transition, characterized by quasi-reversible behaviour with ΔEp values of 0.27–0.34 V and Ipa/Ipc ratios greater thanunity. The results further indicate that electron-donating substituents such as hydroxyl and methoxy groups influencethe electrochemical response of the curcuminoid framework. The study provides important insight into the roleof metal coordination in tuning the redox properties of curcuminoids, which is relevant to their biological and catalyticapplications. The study also supports Sustainable Development Goal 3 (Good Health and Well-being) throughthedevelopment of biologically relevant redox-active coordination compounds.
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