o‐Wurster‐Radikal‐Kationen und ‐Anionen

Abstract

0-Wurster Radical Cations and AnionsSeveral ring-substituted 1,2-phenylenediamines (2,4, 16, 17, 18) as well as their dihydrochlorides may be oxidized electrolytically or by lead dioxide to stable paramagnetic intermediates. Based on the e.s,r. spectra it is concluded that these radicals are cations of the o-Wurster type (C). Their diamagnetic reaction products were found to be am compounds and phenazines. -In the reaction of the phenylenediamines with diphenylthallium hydroxide in the presence of air oxygen the corresponding radical anions (E) are formed. These paramagnetic complexes exhibit a large thallium coupling and are probably ion pairs. The spin density distributed in the phenylenediamine radical cations and anions shows only small differences. -N, N, N', N'-Tetramethyl-1,2-phenylenediamines could not be oxidized under the conditions used. However, N-phosphoranylidene-1,2-phenyIenediamines (25 -27) form stable paramagnetic products after oxidation. These species are radical cations of the Wurster type, too.Brenzcatechine lassen sich im alkalischen Medium durch monovalente Oxidation in die entsprechenden Semichinonanionen A iiberfihren. Daraus entstehen durch eine formale Protonierung die analogen neutralen Aroxyle B, die durch weitere Addition eines Protons schlieDlich die Semichinonkationen-Radikale C bilden konnen. Die% drei Radikaltypen sind schon lange bekannt, und ihre chemischen und physikalischen Eigenschaften sind gut untersucht '). Die neutralen Oxidationsprodukte von o-Aminophenolen D wurden von uns vor einiger Zeit aufgefunden, und ihre spektroskopischen Eigenschaften sowie ihre Reaktionen mit zahlreichen Verbindungs-

Donor-Substituted Diphenylacetylene Derivatives Act as Electron Donors and Acceptors

“…Being one of the most stable organic radicals, Wurster’s radical cations were even among the first to be investigated by EPR spectroscopy . Since then, numerous papers have been published dealing with the radical cations of various p -phenylenediamines. − …”

“…In 1969, a one-electron reduction of an N -trimethylsilyl-substituted p -phenylenediamine to a radical anion was established by means of EPR, , where the success in reducing an electron-rich molecule was explained in terms of a distortion of the n N /π-delocalization due to a twisting of the bulky (Me 3 Si) 2 N groups around the bond between the N and the ring C atom . Further examples are the formation of radical anions of substituted o -phenylenediamine upon treatment with diphenylthallium hydroxide or reaction with alkali-metal mirrors combined with irradiation . Angulo et al published their work on a spectroscopic characterization of tetracyano- p -phenylenediamine, which, although containing the p -phenylenediamine moiety, due to the substitution with four cyano groups becomes a strong oxidant and can be regarded as a tetracyanobenzene rather than as a p -phenylenediamine derivative …”

Artifacts in Amine Analysis from Anodic Oxidation of Organic Solvents upon Electrospray Ionization for Mass Spectrometry

“…if substituents "disturb" each other, as with oNN compared to pNN. 28 In conclusion, the p-phenylenediamines are excellent candidates to generate the M +• ; for pNNNN in particular, with an oxidation potential of 0.1-0.2 V, 27 identity of this species was confirmed. 16 Indeed, for pNNNN, M + H + was not the base peak, but M +• .…”

“…33 Planarity is further expected to support reactivity towards oxidation by reducing the sterical hindrance for mesomeric effects. 28 Thus, the number and intensities of the additional peaks would be expected to vary from compound to compound: However, the intensity of the unknown peaks predominantly followed the intensity of the protonated molecular ion; the highest relative increase was observed for 45meth followed by oNN ( Figure 5). For the N-methyl substituted compounds pNNNN and oNN and the paraphenylenediamines, intensity of M •+ significantly contributed to the abundance of oxidized species.…”