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Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase
Published on: December 4, 2017
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Reversible Electrocatalytic NAD+/NADH Interconversion Mediated by a Pyrazine-Amidate Iridium Complex
Gabriel Menendez Rodriguez1, Caterina Trotta1, Leonardo Tensi2
1Department of Chemistry, Biology, and Biotechnology, Università degli Studi di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy.
Journal of the American Chemical Society
|December 3, 2024
Summary
A new iridium catalyst, [Cp*Ir(pyza)Cl], enables efficient and reversible electrocatalytic conversion between NAD+ and NADH. This catalyst operates at a low overpotential, mimicking the natural redox potential for NAD+/NADH interconversion.
Area of Science:
- Organometallic Chemistry
- Electrocatalysis
- Biomimetic Chemistry
Background:
- Nicotinamide adenine dinucleotide (NAD+/NADH) is a crucial redox cofactor in biological systems.
- Efficient electrocatalytic systems for NAD+/NADH interconversion are vital for bio-inspired energy storage and chemical synthesis.
- Existing electrocatalysts often suffer from high overpotentials, limiting their practical applications.
Purpose of the Study:
- To design and synthesize a novel iridium complex, [Cp*Ir(pyza)Cl], for efficient electrocatalytic NAD+/NADH interconversion.
- To investigate the electrochemical properties and catalytic activity of the new complex.
- To compare its performance with existing catalysts and assess the reversibility of the NAD+/NADH redox couple.
Main Methods:
- Rational catalyst design based on ligand electronic properties (pyrazine amidate vs. picolinamidate).
- Electrochemical characterization including cyclic voltammetry to determine reduction potentials and catalytic activity.
- Nuclear Magnetic Resonance (NMR) spectroscopy, specifically 1H EXSY NMR, to confirm reaction reversibility and equilibrium.
Main Results:
- The synthesized complex [Cp*Ir(pyza)Cl] exhibits significantly lower overpotential for NAD+ reduction (-0.29 V) compared to a related complex (-0.65 V).
- The catalyst operates close to the equilibrium potential of the NAD+/NADH redox couple (E°eq = -0.32 V).
- Reversible electrocatalytic cycling of NAD+ to NADH and NADH to NAD+ was demonstrated, with a catalytic bias towards reduction.
- 1H EXSY NMR confirmed rapid equilibrium of the catalyst-hydride and NADH species, indicating similar hydridicity.
Conclusions:
- [Cp*Ir(pyza)Cl] is a highly effective electrocatalyst for reversible NAD+/NADH interconversion.
- The catalyst's performance is attributed to the electronic properties of the pyrazine amidate ligand, facilitating bielectronic reduction.
- This work provides a promising platform for developing artificial systems that mimic biological redox processes.
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