Effects of the molecular structure on the electrochemical properties of naturally occurring α-hydroxyquinones. An electrochemical and ESR study

Frontana, Carlos; González, Ignacio

doi:10.1016/j.jelechem.2007.01.024

Cited by 32 publications

(13 citation statements)

References 35 publications

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“…The experimentally determined slopes for the above mentioned function were lower than the one expected if electron transfer would the rate determining step (nearly 60 mV per decade), therefore, the observed electrochemical behaviour is related to the presence of a coupled chemical reaction which occurs after the first electron uptake. These results are consistent with the presence of a selfprotonation process , where the presence of hydroxyl functions at positions 2 and 3, afford proton donor sites, which react with the electrogenerated anion radical species, in a father‐son reaction. This selfprotonation reaction sequence is depicted as follows,

true Q - O H + e^{-} \overset{⇀}{↽} {(Q - O H)}^{• -} E_{1}^{0}

true {(Q - O H)}^{• -} + Q - O H \leftrightarrow_{k_{- 1}}^{k_{1}} {(H Q - O H)}^{•} + Q - O^{-} k_{1} ≫ k_{- 1}

true {(H Q - O H)}^{•} + e^{-} \overset{⇀}{↽} {(H Q - O H)}^{-} E_{2}^{0}

…”

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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true Q - O H + e^{-} \overset{⇀}{↽} {(Q - O H)}^{• -} E_{1}^{0}

true {(Q - O H)}^{• -} + Q - O H \leftrightarrow_{k_{- 1}}^{k_{1}} {(H Q - O H)}^{•} + Q - O^{-} k_{1} ≫ k_{- 1}

true {(H Q - O H)}^{•} + e^{-} \overset{⇀}{↽} {(H Q - O H)}^{-} E_{2}^{0}

…”

Section: Resultsmentioning

confidence: 99%

“…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%

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 general, the overall rate of the ECE reaction scheme (reactions (2), (13), (15), (16), (17), (18)) needed to be increased as the water concentration was increased.…”

Section: Mechanism Of Reduction At the First Peak In The Presence Of mentioning

confidence: 99%

Effect of hydroxylic additives on the electrochemical reduction of some azobenzenes

Sánchez¹,

Evans²

2010

Journal of Electroanalytical Chemistry

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“…However, up to present, a systematic and comparative analysis of the electrochemical properties of dihydroxy-anthraquinones and an assessment of their suitability for the reduction of dispersed indigo is not available in the literature [20][21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Indirect cathodic reduction of dispersed CI Vat Blue 1 (indigo) by dihydroxy-9,10-anthraquinones in cyclic voltammetry experiments

Turcanu¹,

Fitz-Binder²,

Bechtold³

2011

Journal of Electroanalytical Chemistry

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Effects of the molecular structure on the electrochemical properties of naturally occurring α-hydroxyquinones. An electrochemical and ESR study

Cited by 32 publications

References 35 publications

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

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

Effect of hydroxylic additives on the electrochemical reduction of some azobenzenes

Indirect cathodic reduction of dispersed CI Vat Blue 1 (indigo) by dihydroxy-9,10-anthraquinones in cyclic voltammetry experiments

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