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Updated: Jul 13, 2026
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Surface Functionalization of Metal-Organic Frameworks for Improved Moisture Resistance
Published on: September 5, 2018
Effect of group II metal cations on catecholate oxidation
Alexander V Lebedev1, Marina V Ivanova, Alexander A Timoshin
1Department of Biochemistry, Institute of Experimental Cardiology, Cardiology Research Center, 3rdCherepkovskaya Street 15A, 121552 Moscow, Russia. avleb@cardio.ru
Summary
Calcium ions (Ca2+) unexpectedly accelerate the oxidation of catechols by increasing hydroxyl group dissociation and promoting the formation of stable free radicals. This enhances their susceptibility to oxygen-induced oxidation, impacting biological processes.
Area of Science:
- Biochemistry
- Chemical Kinetics
- Free Radical Chemistry
Background:
- Catechol autoxidation is a complex process involving free-radical chain reactions.
- The influence of metal ions on these reactions is not fully understood.
- Dopamine and norepinephrine are biologically relevant catechols whose oxidation is of interest.
Purpose of the Study:
- To investigate the unexpected effects of calcium ions (Ca2+) on catechol oxidation.
- To elucidate the mechanisms by which Ca2+ influences free-radical chain reactions.
- To compare the effects of Ca2+ with other alkaline-earth metal cations and Zn2+.
Main Methods:
- Oxygen consumption measurements
- Electron Paramagnetic Resonance (EPR) spectroscopy
- UV/VIS spectrophotometry
- Potentiometric titration
Main Results:
- Ca2+ forms catecholate complexes, increasing phenolic hydroxyl dissociation constants (K(ai)).
- Alkaline-earth metal cations (Ca2+, Mg2+) accelerate catecholate oxidation at pH > pK(ai), while Zn2+ decreases the rate.
- Metal-catecholate complexes exhibit increased susceptibility to dioxygen-induced oxidation.
- Transient increases in EPR signals for metal-semiquinonate complexes were observed.
Conclusions:
- Ca2+ and other alkaline-earth metal cations promote catechol autoxidation through additional deprotonation and formation of more oxidizable complexes.
- These cations facilitate the formation of stable free-radical intermediates that propagate the oxidation chain.
- The findings provide new insights into metal ion modulation of catechol redox chemistry.
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