Studies of the electrochemical reduction of some dinitroaromatics

Revisiting the electrochemical formation, stability and structure of radical and biradical anionic structures in dinitrobenzenes

“…For instance, the reduction of molecules bearing two nitro groups has gained attention in recent years [5][6][7][8] mainly due to the effects occurring in the stabilization of the corresponding electrogenerated radical anions by interacting groups present in the structure, since this phenomenon is known to be dependent on the environment surrounding the radical anion and on the method employed for its formation [6][7][8][9]. This issue is relevant, in biological and pharmacological terms, once the stability of the electrogenerated radical species is related to the capacity of these species to induce the formation of reactive oxygen species, in the presence of oxygen and after reduction [2][3][4][10][11][12] that in vivo or in cell occurs via the action of nitroreductases [2,11,12].…”

“…Nitroaromatic compounds reduction give more stable radical anions or dianions than nitroaliphatic ones, due to charge delocalization by resonance effects, where in some cases, like paradinitrobenzene, it is observed a large contribution of a quinonoidic type structure, which must have the major contribution to the true structure [8]. This stabilization may promote bond break at substituent-aromatic ring positions, such as bromine and iodine [16,17], or simple proton dissociation of phenol or carboxylic acid derivatives [18].…”

“…1), evidence was found of complete delocalization of the spin of the radical anion A •− (Eq. (1)) on both nitro groups through the aromatic ring [8,9]. Also, a second electron transfer yields a dianion species which, having no unpaired electrons, did not give an ESR signal.…”

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

“…The electrochemical redox process, including the possible electrode reactions and proton-transfer reactions, can be depicted by the well-known nine-membered square scheme [6,16,17]. Dimerization is one of the significant organic radical reactions [18][19][20][21][22][23].…”

Electron Transfer and Structural Change: Distinguishing Concerted and Two‐Step Processes

“…For example, the rate constants for isomerization of the radical anions of 6 and 7 have been estimated to be of the order of 10 5 s À1 by voltammetric studies. [12,13] In addition to the rather large rates of isomerization, the similarity of E o 1A and E o 1B in the cases of 6 and 7 also makes difficult the unambiguous detection of the intermediate. Nevertheless, these reactions can be assigned with confidence to be two-step processes, electron transfer followed by structural change.…”