Spectroelectrochemical studies of TDMQ20: A potential drug against Alzheimer's disease - part 2 - Cu-complexes

Alzheimer's Disease (AD) has been associated with the overproduction reactive radicals through the catalytic effect of β-amyloid peptide Cu(II) complexes. In this article, we performed electrochemical characterisation of copper complexed with TDMQ20, which has been suggested as a potential drug against AD, using electrochemistry and spectroelectrochemistry (SEC). Based on voltammetry, we showed that oxidation as well as reduction processes of Cu(II)-TDMQ20 are pH-sensitive. Simulations of the CVs allowed us to estimate the kinetic parameters of the initial quasi-reversible oxidation of Cu(II) and the subsequent internal electron transfer to the Cu(III) ion from the TDMQ20 ligand (k₀ ≈ 18 s^-1). The electrochemical mechanism of oxidation/reduction of Cu(II)-TDM20 complex was also studied using UV-VIS absorption spectroelectrochemistry (UV-VIS SEC). UV-VIS SEC measurements showed that after oxidation of the ligand through the reduction of the Cu(III), the Cu remains complexed with the TDMQ20, but the electrochemical properties of the complex are changed. Our findings contribute to a broader understanding of the redox activity of the Cu(II)-TDMQ20 complex at physiological pH, which is a crucial aspect in evaluating the potential clinical utility of this compound.