Electrochemical behaviour of new dimeric esters and amides derived from caffeic acid in dimethylsulfoxide

Abstract

The electrochemical oxidation in DMSO of four new derivatives of caffeic acid (CA), two dimeric amides and two dimeric esters, is reported in this article. Although all of them contain two caffeoyl electroactive moieties in their structures, small differences in the connectors result in interesting changes in the electrochemical behaviour of this type of compound. Voltammograms of both esters do not show appreciable differences between them; however, an electrografting process occurs during the electrochemical oxidation of one of them, which suggests that the identity of the connector has an influence on the ability of the diesters to interact with the electrode surface. On the other hand, voltammograms of dimeric amides were more complex than those corresponding to dimeric esters. Electronic effects of diamine connectors seem to be related to the fact that caffeoyl moieties suffer from separate oxidation processes in both compounds. In contrast to their ferulic acid (FA) analogues, which have been studied by our group before, CA dimeric amides do not interact in an appreciable way with the electrode surface. In addition, a relationship between the oxidation potential and the inhibition percentage of the DPPH (2,2'-diphenyl-1-picrylhydrazyl) radical was not observed for the symmetrical CA derivatives studied here. However, the molecular flexibility seems to play a very important role in the Free Radical Scavenging Activity (FRSA) of this type of compound.

Grafting of the carbon allotropes and polypyrrole via a Kevlar-type organic linker: the correlation of carbon structure/morphology with electrochemistry of the composite electrode

“…Consequentially, reverse cathodic scan introduces electrons into the poly(pyrrole) and conveys it to the neutral state. The oxidation peak at -0.15 V is related to the redox activity of the amide linker [59]. Furthermore, the influence of carbon type or/and the morphology of the grafted material is studied using a differential voltammetry that allows to better resolve the corresponding peaks.…”

“…Possibly, the positive shift of the onset potential of this redox is a catalytic effect of the sp 2 edges in the graphene and CNHs. Another important observation is the catalytic activity towards oxygen reduction at 0.21 V, taking place onto the oxygen-containing functionalities and the sp 2 carbon active centers [59,60,61] for the graphene (Fig. 7b), and occurs as a very weak signal at 0.27 V for the CNH-based capacitor (Fig.…”

Effect of 1‐ethyl‐3‐methylimidazolium acetate on the oxidation of caffeic acid benzyl ester: An electrochemical and theoretical study

“…Similitudes between the voltammogram of CABE and those reported before, for caffeic acid and for some of its ester and amides derivatives in aprotic media, allow us to infer that the oxidation of CABE follows an electrochemical‐chemical‐electrochemical (ECE) mechanism, which involves the loss of an electron from the catechol moiety, followed by a fast deprotonation reaction and the subsequent loss of a second electron.…”

Mechanism of Chicoric Acid Electrochemical Oxidation and Identification of Oxidation Products by Liquid Chromatography and Mass Spectrometry

“…It was reported by Sánchez et al. that caffeic acid related derivatives, two dimeric amides and two dimeric esters, are electrochemically oxidized involving the catechol group via two‐step mechanism. Investigation of the electrochemical oxidation mechanisms of verbascoside and rosmarinic acid, caffeic acid esters with two catechol moieties, was reported by Gil et al.…”