Electrochemical Reduction of 4‐Nitrobenzyl Phenyl Thioether for Activation and Capture of CO₂

Abstract

In this work, a new simple molecule, 4-nitrobenzyl phenyl thioether (1), is prepared and used for controlling and tuning CO 2 reactivity in function of the electrode potential. The first part of the study is devoted to determining the electrochemical reduction mechanism of 1 in N,N-dimethylformamide under nitrogen. The compound shows a first reversible one-electron transfer process, whereas the reaction cleavage of the CÀ S bond takes place after a second electron transfer process through a stepwise mechanism (thermodynamic and kinetic parameters are conveniently determined). In the second part of the study, the inert atmosphere was replaced by a CO 2 atmosphere. At low potential values, compound 1 acts as a redox mediator that allows the reduction of CO 2 at ca. À 1.2 V vs. SCE. The electrochemical generation of 1 2À at more negative potential values leads to a CÀ S bond cleavage reaction that yields the corresponding nitrobenzyl and thiosulfate anions, which react with CO 2 . The nitro aromatic anion derivative makes it possible to obtain electrocarboxylated derivatives, whereas the thiophenolate anion captures CO 2 reversibly. Hence, this research opens a new way of tuning and controlling the reaction processes associated with CO 2 from homogenous catalysis at low negative potentials, to electrocarboxylation processes passing to CO 2 reversible electrochemically triggered adsorption processes.

Electroreductive Deoxygenative C−H and C−C Bond Formation from Non‐Derivatized Alcohols Fueled by Anodic Borohydride Oxidation

“…Likewise, it cannot be ruled out that CO 2 radical anions can act as reductive electron transfer mediators for certain substrates as reported for electroreduction of benzoate esters and thioethers. [16,90] It can be noted that alkyl carbonates were not observed in the reaction mixture by NMR, suggesting a distinctly different mechanism for the deoxygenative carboxylation compared to the in situ formed carbonate intermediate reported by Senboku and co-workers. [73] It is well established in fuel cell applications that borohydride compounds can undergo electrooxidation to generate H 2 , [81][82][83]91,92] and bubble formation at the anode suggested that this is a likely path in the present system.…”

“…As such, it cannot be ruled out that the C−C bond formation may also proceed via radical‐radical coupling of benzylic open shell intermediates and CO 2 radical anions (ESI, Section 12) and that the contribution of different pathways is substrate dependent. Likewise, it cannot be ruled out that CO 2 radical anions can act as reductive electron transfer mediators for certain substrates as reported for electroreduction of benzoate esters and thioethers [16,90] . It can be noted that alkyl carbonates were not observed in the reaction mixture by NMR, suggesting a distinctly different mechanism for the deoxygenative carboxylation compared to the in situ formed carbonate intermediate reported by Senboku and co‐workers [73] …”

Mechanism of CO2 Capture and Release on Redox-Active Organic Electrodes

“…This effort is in an early stage. In fact, many of the stimulus-responsive adsorbent materials also require high energy to release captured CO 2 and regenerate the original state. ,, Electric-swing adsorption (ESA) can minimize such energy losses in stimuli-responsive adsorbent materials because the adsorbent materials can be operated with much higher efficiency than the TSA and pressure-swing adsorption (PSA) processes. − …”

Electrocarboxylation of Spiropyran Switches through Carbon‐Bromide Bond Cleavage Reaction

“…Actually, the chemical synthesis of carboxylic acids and their derivatives (e. g., esters or amides) imply the use of many reagents, catalysts [33] or organolithium compounds [34] at mild or strong conditions [35,36] . In this context, the electrochemical carboxylation of organic molecules to produce carboxylic acids by fixing carbon dioxide has emerged during the last years as an efficient green route compared to conventional chemical synthetic methods, especially since this process can be performed efficiently under mild conditions at atmospheric pressure and avoiding the use of additional reagents [37–42] . One of the most popular electrocarboxylation strategies of organic compounds is based on the in situ formation of a carbanion via reduction, which in turn undergoes a nucleophilic addition to CO 2 to yield the carboxylate functional group (Figure 2).…”

“…[35,36] In this context, the electrochemical carboxylation of organic molecules to produce carboxylic acids by fixing carbon dioxide has emerged during the last years as an efficient green route compared to conventional chemical synthetic methods, especially since this process can be performed efficiently under mild conditions at atmospheric pressure and avoiding the use of additional reagents. [37][38][39][40][41][42] One of the most popular electrocarboxylation strategies of organic compounds is based on the in situ formation of a carbanion via reduction, which in turn undergoes a nucleophilic addition to CO 2 to yield the carboxylate functional group (Figure 2). [43] The success of this approach is strongly related to the stability (i. e., lifetime) of the anion formed in the electrolytic medium.…”