DFT/B3LYP study of the substituent effect on the reaction enthalpies of the individual steps of single electron transfer–proton transfer and sequential proton loss electron transfer mechanisms of chroman derivatives antioxidant action

2011 ◽  
Vol 969 (1-3) ◽  
pp. 1-12 ◽  
Author(s):  
Meysam Najafi ◽  
Kaveh Haghighi Mood ◽  
Mansour Zahedi ◽  
Erik Klein
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Substituent Effect ◽  
Single Electron ◽  
Single Electron Transfer ◽  
Antioxidant Action ◽  
The Individual ◽  
Transfer Mechanisms ◽  
Proton Loss

scholarly journals Radical Biocatalysis: Using Non-Natural Single Electron Transfer Mechanisms to Access New Enzymatic Functions

Synlett ◽  
2019 ◽  
Vol 31 (03) ◽  
pp. 248-254 ◽  
Author(s):  
Todd K. Hyster
Keyword(s):  
Electron Transfer ◽  
Active Sites ◽  
Hydrogen Atom Transfer ◽  
Single Electron ◽  
Great Promise ◽  
Single Electron Transfer ◽  
Radical Intermediates ◽  
Redox Activation ◽  
Transfer Mechanisms ◽  
Ground State Electron

Exploiting non-natural reaction mechanisms within native enzymes is an emerging strategy for expanding the synthetic capabilities of biocatalysts. When coupled with modern protein engineering techniques, this approach holds great promise for biocatalysis to address long-standing selectivity and reactivity challenges in chemical synthesis. Controlling the stereochemical outcome of reactions involving radical intermediates, for instance, could benefit from biocatalytic solutions because these reactions are often difficult to control by using existing small molecule catalysts. General strategies for catalyzing non-natural radical reactions within enzyme active sites are, however, undeveloped. In this account, we highlight three distinct strategies developed in our group that exploit non-natural single electron transfer mechanisms to unveil previously unknown radical biocatalytic functions. These strategies allow common oxidoreductases to be used to address the enduring synthetic challenge of asymmetric hydrogen atom transfer.1 Introduction2 Photoinduced Electron Transfer from NADPH3 Ground State Electron Transfer from Flavin Hydroquinone4 Enzymatic Redox Activation in NADPH-Dependent Oxidoreductases5 Conclusion

Divergence between Organometallic and Single-Electron-Transfer Mechanisms in Copper(II)-Mediated Aerobic C–H Oxidation

2013 ◽  
Vol 135 (26) ◽  
pp. 9797-9804 ◽  
Author(s):  
Alison M. Suess ◽  
Mehmed Z. Ertem ◽  
Christopher J. Cramer ◽  
Shannon S. Stahl
Keyword(s):  
Electron Transfer ◽  
Single Electron ◽  
Single Electron Transfer ◽  
Transfer Mechanisms

scholarly journals Inhibited proton transfer enhances Au-catalyzed CO2-to-fuels selectivity

2016 ◽  
Vol 113 (32) ◽  
pp. E4585-E4593 ◽  
Author(s):  
Anna Wuttig ◽  
Momo Yaguchi ◽  
Kenta Motobayashi ◽  
Masatoshi Osawa ◽  
Yogesh Surendranath
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Active Sites ◽  
Carbonic Acid ◽  
Kinetic Studies ◽  
Single Electron ◽  
Ir Absorption ◽  
Single Electron Transfer ◽  
Mechanistic Basis ◽  
Rate Limiting

CO2 reduction in aqueous electrolytes suffers efficiency losses because of the simultaneous reduction of water to H2. We combine in situ surface-enhanced IR absorption spectroscopy (SEIRAS) and electrochemical kinetic studies to probe the mechanistic basis for kinetic bifurcation between H2 and CO production on polycrystalline Au electrodes. Under the conditions of CO2 reduction catalysis, electrogenerated CO species are irreversibly bound to Au in a bridging mode at a surface coverage of ∼0.2 and act as kinetically inert spectators. Electrokinetic data are consistent with a mechanism of CO production involving rate-limiting, single-electron transfer to CO2 with concomitant adsorption to surface active sites followed by rapid one-electron, two-proton transfer and CO liberation from the surface. In contrast, the data suggest an H2 evolution mechanism involving rate-limiting, single-electron transfer coupled with proton transfer from bicarbonate, hydronium, and/or carbonic acid to form adsorbed H species followed by rapid one-electron, one-proton, or H recombination reactions. The disparate proton coupling requirements for CO and H2 production establish a mechanistic basis for reaction selectivity in electrocatalytic fuel formation, and the high population of spectator CO species highlights the complex heterogeneity of electrode surfaces under conditions of fuel-forming electrocatalysis.

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