ChemInform Abstract: Redox Chemistry of Substituted Benzenes. The One-Electron Reduction Potentials of Methoxy-Substituted Benzene Radical Cations

Nitroaromatic compounds—adducts of Morita–Baylis–Hillman (MBHA) reaction—have been applied in the treatment of malaria, leishmaniasis, and Chagas disease. The biological activity of these compounds is directly related to chemical reactivity in the environment, chemical structure of the compound, and reduction of the nitro group. Because of the last aspect, electrochemical methods are used to simulate the pharmacological activity of nitroaromatic compounds. In particular, previous studies have shown a correlation between the one-electron reduction potentials in aprotic medium (estimated by cyclic voltammetry) and antileishmanial activities (measured by the IC50) for a series of twelve MBHA. In the present work, two different computational protocols were calibrated to simulate the reduction potentials for this series of molecules with the aim of supporting the molecular modeling of new pharmacological compounds from the prediction of their reduction potentials. The results showed that it was possible to predict the experimental reduction potential for the calibration set with mean absolute errors of less than 25 mV (about 0.6 kcal·mol−1).

Download Full-text

Relative One-Electron Reduction Potentials of Carotenoid Radical Cations and the Interactions of Carotenoids with the Vitamin E Radical Cation

Journal of the American Chemical Society ◽

10.1021/ja974191q ◽

1998 ◽

Vol 120 (17) ◽

pp. 4087-4090 ◽

Cited By ~ 91

Author(s):

Ruth Edge ◽

Edward J. Land ◽

David McGarvey ◽

Louise Mulroy ◽

T. George Truscott

Keyword(s):

Vitamin E ◽

Radical Cation ◽

Radical Cations ◽

Reduction Potentials ◽

Electron Reduction

Download Full-text

The one-electron reduction potentials of NAD

Biochimica et Biophysica Acta (BBA) - Bioenergetics ◽

10.1016/0005-2728(80)90031-6 ◽

1980 ◽

Vol 590 (2) ◽

pp. 273-276 ◽

Cited By ~ 51

Author(s):

John A. Farrington ◽

Edward J. Land ◽

A.John Swallow

Keyword(s):

Reduction Potentials ◽

Electron Reduction ◽

The One

Download Full-text

Electrochemical properties and catalytic reactivity of cobalt complexes with redox-active meso-substituted porphycene ligands

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424619500780 ◽

2020 ◽

Vol 24 (01n03) ◽

pp. 90-97 ◽

Cited By ~ 1

Author(s):

Taro Koide ◽

Zihan Zhou ◽

Ning Xu ◽

Yoshio Yano ◽

Toshikazu Ono ◽

...

Keyword(s):

Reduction Potential ◽

Energy Levels ◽

Cobalt Complexes ◽

Alkyl Halides ◽

Reduction Potentials ◽

Positive Side ◽

Redox Active ◽

Catalytic Reactivity ◽

Electron Reduction ◽

The One

The cobalt complexes of meso-aryl substituted porphycenes were synthesized and characterized. The reduction potentials of the complexes were shifted to the positive side depending on the strength of the electron-withdrawing properties of the meso-substituents, while the optical properties, such as the absorption spectra of these complexes, were similar. This suggests that the energy levels of the molecular orbitals of the complexes were changed by the meso-substituents while the gaps of the orbitals were not significantly changed. The one-electron reduction of the complex did not afford the Co(I) species, but the ligand-reduced radical anion, which was characterized by electrospectrochemistry. The generated ligand-reduced species reacted with alkyl halides to form the Co(III)-alkyl complex. As a result, the reduction potential of the electrolytic reaction could be directly controlled by the substituents of the porphycene. The catalytic reaction with trichloromethylbenzene was also performed and it was found that the ratio of the obtained products was changed by the reduction potentials of the catalyst, [Formula: see text]. the cobalt porphycenes.

Download Full-text

Reduction of ferric haemoproteins by tetrahydropterins: a kinetic study

Biochemical Journal ◽

10.1042/bj20050437 ◽

2005 ◽

Vol 392 (3) ◽

pp. 583-587 ◽

Cited By ~ 10

Author(s):

Chantal Capeillere-Blandin ◽

Delphine Mathieu ◽

Daniel Mansuy

Keyword(s):

Electron Transfer ◽

Cytochrome C ◽

Cytochrome B5 ◽

Reduction Rate ◽

Cation Radical ◽

Order Reduction ◽

Reduction Potentials ◽

Electron Reduction ◽

The One

We previously showed that one-electron transfer from tetrahydropterins to iron porphyrins is a very general reaction, with formation of an intermediate cation radical similar to the one detected in NO synthase. As a model reaction, the rates of reduction of eight haemoproteins by diMePH4 (6,7-dimethyltetrahydropterin) have been studied and correlated with their one-electron reduction potentials, Em (FeIII/FeII). On the basis of kinetic data analyses, a bimolecular collisional mechanism is proposed for the electron transfer from diMePH4 to ferrihaemoproteins. Haemoproteins with reduction potentials below −160 mV were shown not to be reduced by diMePH4 to the corresponding ferrohaemoproteins. For haemoproteins with reduction potentials more positive than −160 mV, such as chloroperoxidase, cytochrome b5, methaemoglobin and cytochrome c, there was a good correlation between the second-order reduction rate constant and the redox potential, Em (FeIII/FeII):The rate of reduction of cytochrome c by BH4 [(6R)-5,6,7,8-tetrahydrobiopterin] was determined to be similar to that of the reduction of cytochrome c by diMePH4. These results confirm the role of tetrahydropterins as one-electron donors to FeIII porphyrins.

Download Full-text

Elektronentransfer und Ionenpaar-Bildung, 33 [1, 2]. Die Einelektronen-Reduktion von Tetraphenyl-p-benzochinon mit Alkalimetallen: ENDOR-Spektren von Kontaktionen-Paaren sowie Tripelionen in Lösung und Einkristallstrukturen der Neutralverbindung und ihres Natrium-Salzes / Electron Transfer and Ion Pair Formation, 33 [1,2]. The Single Electron Reduction of Tetraphenyl-p-benzoquinone by Alkali Metals: ENDOR Spectra of Contact Ion Pairs as well as Triple Ions in Solution and Single Crystal Structures of Both the Neutral Compound and its Sodium Salt

Zeitschrift für Naturforschung B ◽

10.1515/znb-1994-0416 ◽

1994 ◽

Vol 49 (4) ◽

pp. 529-541 ◽

Cited By ~ 7

Author(s):

Hans Bock ◽

Andreas John ◽

Markus Kleine ◽

Christian Näther ◽

Jan W. Bats

Keyword(s):

Single Crystal ◽

Radical Anion ◽

Alkali Metals ◽

Ion Pairs ◽

Radical Cations ◽

Chair Conformation ◽

Reduction Potentials ◽

Half Wave ◽

Electron Reduction ◽

Contact Ion Pairs

Tetraphenyl-p-benzoquinone, according to its single crystal structure, shows some steric congestion: its quinone ring is distorted by 7° to a chair conformation, and its phenyl substituents are twisted around their CC axes between 46° and 72°. The half-wave reduction potentials of -0.57 and -1.25 V in acetonitrile confirm negligible π interaction of the phenyl substituents. Addition of alkalimetal tetraphenylborate salts lowers the second reduction potential due to contact ion formation, which can be confirmed by UV/VIS spectra recorded under aprotic conditions. Extensive ESR/ENDOR investigations prove the formation of the following species in THF solution: Tetraphenyl-p-benzosemiquinone radical anion contact ion pairs [M·⊖ Me⊕solv]' (Me⊕: Li⊕, Na⊕, Rb⊕, Cs⊕) and contact triple ion radical cations both with identical cations [M·⊖ (Me⊕solv)2]·⊕ (Me⊕: Li⊕, Na⊕, Cs⊕) and different cations [M·⊖ (Li⊕solv)(Me⊕solv)]·⊕ (Me⊕: Na⊕, Cs⊕). Addition of crown ethers can lead to external solvation of the Me⊕ counter cations, whereas cryptands form internal solvation complexes. The radical anion of 2,6-diphenyl-p-benzosemiquinone adds cations at its phenyl-free molecular half. The radical anion salt [tetraphenyl-p-benzosemiquinone·⊖ (Na⊕(tetrahydropyrane) 2)] could be crystallized and its structure determined at 200 K. In agreement with the Hirota sign rules for contact radicals in solution, the Na⊕ ion is found 62 pm above the π plane and 29° outside the axis of the CO bound, which is elongated due to one-electron reduction by 5 pm to 127 pm.

Download Full-text