Mechanistic insights into the redox reactions of chromium complexes containing picolinates as ligands, interaction with biomolecules

Proton-coupled electron transfer (PCET) is a common reaction in biological systems, with potential implications for DNA damage and repair. This study showed that tris-(2-pyridine carboxylate) chromium (III) (complex 1) exhibited an increased electrochemical reaction rate in the presence of a strong acid, suggesting that PCET via proton donation promotes the reduction reaction. Conversely, complex 1 with picolinic acid showed a decreased electrochemical exchange constant, suggesting kinetic control by slow electronic exchange, consistent with PCET. Bis(pyridine-2,6-dicarboxylate) chromate (III) of sodium (complex 2), showed potential shifts and broadening of signals in the presence of dipicolinic and ascorbic acids, further supporting the involvement of PCET. Overall, the study highlighted the modulation of the electrochemical behavior of the chromium complexes through proton-coupled shifts in reduction potentials and kinetics, shedding light on their potential interactions with cellular reductant agents and protons. The weaker interactions of complexes 1 and 2 with BSA and DNA, together with their lower bioavailability and solubility compared to CQDP, contribute to our understanding of the potential biological effects of the chromium complexes studied. This abstract provides a comprehensive overview of the results of the study, highlighting the significance of the PCET reactions and their potential implications for biological processes and health effects.