Electrochemical and chemical formation of a low-barrier proton transfer complex between the quinone dianion and hydroquinone

Astudillo, Pablo D.; Valencia, Drochss P.; González‐Fuentes, Miguel A.; Díaz-Sánchez, Blanca R.; Frontana, Carlos; González, Felipe J.

doi:10.1016/j.electacta.2012.07.078

Cited by 36 publications

(40 citation statements)

References 65 publications

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“…4,10,11,13 Gupta and Linschitz 4 appear to be the first to offer an explanation. They proposed that the small second CV wave could be due to the formation of an electroinactive dimer between the quinone dianion and the starting quinone, Rxn 1 in Scheme 1.…”

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confidence: 91%

The Effect of Glassy Carbon Surface Oxides in Non-Aqueous Voltammetry: The Case of Quinones in Acetonitrile

et al. 2014

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Glassy carbon (GC) electrodes are well-known to contain oxygenated functional groups such as phenols, carbonyls, and carboxylic acids on their surface. The effects of these groups on voltammetry in aqueous solution are well-studied, but there has been little discussion of their possible effects in nonaqueous solution. In this study, we show that the acidic functional groups, particularly phenols, are likely causes of anomalous features often seen in the voltammetry of quinones in nonaqueous solution. These features, a too small second cyclic voltammetric wave and extra current between the two waves that sometimes appears to be a small, broad third voltammetric wave, have previously been attributed to different types of dimerization. In this work, concentration-dependent voltammetry in acetonitrile rules out dimerization with a series of alkyl-benzoquinones because the anomalous features get larger as the concentration decreases. At low concentrations, solution bimolecular reactions will be relatively less important than reactions with surface groups. Addition of substoichiometric amounts of naphthol at higher quinone concentrations produces almost identical behavior as seen at low quinone concentrations with no added naphthol. This implicates hydrogen bonding and proton transfer from the surface phenolic groups as the cause of the anomalous features in quinone voltammetry at GC electrodes. This conclusion is supported by the perturbation of surface oxide coverage on GC electrodes through different electrode pretreatments.

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confidence: 91%

The Effect of Glassy Carbon Surface Oxides in Non-Aqueous Voltammetry: The Case of Quinones in Acetonitrile

et al. 2014

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“…In this particular case, the current is smaller than the expected ratio, however, a broad signal was observed at potential values between peaks Ic and IIc (Figure C). This signal can possibly be related to the reduction of intermolecular hydrogen bonded products formed between reduced intermediates generated during the selfprotonation step . Such behavior is consistent with the above described spectroelectrochemical‐ESR analysis, where the distinctive hyperfine coupling pattern is related to a high spin symmetry structure, which can only be explained if the compound being reduced is not directly the deprotonated form, but a hydrogen bonded dimer of this species.…”

Section: Resultsmentioning

confidence: 87%

“…This proposal was verified by performing electrochemical experiments in the presence of tetrabutylammonium hydroxide (nBu 4 NOH), as a deprotonating agent . The obtained voltammograms are presented in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…This pattern is significantly different from the one expected, due to the lack of symmetry elements in the structure (a C 1 point group). Thereby, the observed spectrum could be explained considering the formation of a radical dimer interacting between the π planes of the naphthoquinone structure, thus providing symmetry in atoms HFCC values of the proposed adduct , compared with the expected asymmetrical spin density distribution (Fig. C).…”

Section: Resultsmentioning

confidence: 99%

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Intramolecular Hydrogen Bonding/Selfprotonation Processes Modulated by the Substituent Effect in Hydroxyl‐substituted Naphthoquinones

Maldonado¹,

Martínez‐González²,

Frontana³

2016

Electroanalysis

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In this work, an electrochemical and spectroelectrochemical ESR study for a series of hydroxyl substituted 1,4‐naphthoquinones is presented. Results show that the electrochemical behaviour is dependent on the relative positions of these groups within the molecules. For compounds which have hydroxyl groups at the annellated benzene ring, intramolecular hydrogen bonding (a substituent field effect) determines the energy of reduction of the system. When hydroxyl functions are located at the C‐2 or C‐3 positions, a selfprotonation process occurs. The electrogenerated dianion or trianion radicals, derived from deprotonated quinones, show that intramolecular hydrogen bonding has a significant effect both in the spin density distribution and in the energy required for the formation of these radical species. The difference observed in the slope for EpIc vs. log v function for 2,3,5,8‐tetrahydroxy‐1,4‐naphthoquinone suggest that, for this compound, the proton transfer step does not occur as a single, but as a two‐step sequence, where an hydrogen bonded adduct could be present as a stable intermediate. These processes could help to explain the discrepancies observed earlier performing linear free energy relationships these compounds.

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“…The electrochemical reduction of quinones has been studied widely [1][2][3][4][5][6]. The study can not only provide the redox mechanism, but also help us understand the different roles which quinones and their intermediates play in the electron transfer process in living organisms [7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Investigation on redox mechanism of 1,4-naphthoquinone by in situ FT-IR spectroelectrochemistry

Chen

Jin

2015

Journal of Electroanalytical Chemistry

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Electrochemical and chemical formation of a low-barrier proton transfer complex between the quinone dianion and hydroquinone

Cited by 36 publications

References 65 publications

The Effect of Glassy Carbon Surface Oxides in Non-Aqueous Voltammetry: The Case of Quinones in Acetonitrile

The Effect of Glassy Carbon Surface Oxides in Non-Aqueous Voltammetry: The Case of Quinones in Acetonitrile

Intramolecular Hydrogen Bonding/Selfprotonation Processes Modulated by the Substituent Effect in Hydroxyl‐substituted Naphthoquinones

Investigation on redox mechanism of 1,4-naphthoquinone by in situ FT-IR spectroelectrochemistry

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