Considering the electrochemical behavior of xanthones XH3 and XH7 regarding the peak potential separation (DEp), one could observe that for pH 7.4 and 11.0, the Epc–Epa values 30–35 mV
point to the involvement of two-electrons in the oxidation reaction on the glassy carbon electrode. The results suggest that the catechol moiety of the xanthone core is implied in a two-electron two-proton redox process, leading to the formation of orthoquinone-type intermediates.36 In acidic medium, the separation of the redox peak potentials DEp was 66 mV and 159 mV for XH7 and XH3, respectively. We can postulate that the mechanism behind the oxidation of XH7 involves the formation of a semiquinone intermediate which suffers disproportionation with formation of the ortho-quinone derivative and simultaneous regeneration of XH7. These results are consistent with our previous report on the oxidation mechanism of 2-styrylchromones possessing a catechol moiety.
When the potential scan was inverted before the second oxidation peak, the DEp value of xanthones XH6 and XH8 at pH 7.4 and 11.0 decreased to approximately 52–54 mV, corresponding to
one-electron oxidation. Slightly changes occurred at pH 4.0 showing high DEp values.
Considering the electrochemical behavior of xanthones XH3 and XH7 regarding the peak potential separation (DEp), one could observe that for pH 7.4 and 11.0, the Epc–Epa values 30–35 mVpoint to the involvement of two-electrons in the oxidation reaction on the glassy carbon electrode. The results suggest that the catechol moiety of the xanthone core is implied in a two-electron two-proton redox process, leading to the formation of orthoquinone-type intermediates.36 In acidic medium, the separation of the redox peak potentials DEp was 66 mV and 159 mV for XH7 and XH3, respectively. We can postulate that the mechanism behind the oxidation of XH7 involves the formation of a semiquinone intermediate which suffers disproportionation with formation of the ortho-quinone derivative and simultaneous regeneration of XH7. These results are consistent with our previous report on the oxidation mechanism of 2-styrylchromones possessing a catechol moiety. When the potential scan was inverted before the second oxidation peak, the DEp value of xanthones XH6 and XH8 at pH 7.4 and 11.0 decreased to approximately 52–54 mV, corresponding toone-electron oxidation. Slightly changes occurred at pH 4.0 showing high DEp values.
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