Electron spin resonance measurements have been made on dimethyl sulfoxide solutions of the anion radicals of s‐tetrazine, pyridazine, phthalazine, and phenazine, as well as the diprotopyrazine cation radical. The radicals were generated by constant potential electroreduction of the parent compound at a mercury pool cathode within the microwave cavity. Complete assignment of the hyperfine coupling constants to positions of phthalazine anion was made by selective deuteration and the help of a spectral synthesis program. Satellites due to the C13 hyperfine interaction of pyrazine anion have been observed, and the coupling constant measured. The mechanism of N14 hyperfine interactions in polyazine anion radicals is discussed in terms of earlier theories of C13 interaction. We find that π‐electron spin density on nearest‐neighbor N atoms affects aN strongly, whereas on nearest‐neighbor C atoms it does not. Values for several empirically determined spin‐polarization parameters are reported.

Electron Spin Resonance Studies of the Diazine Negative Ions

ESR Study of Polyazine Anions

https://pure.rug.nl/ws/files/14661681/1972ChemPhysLettJonkman.PDF

The UV Spectra and Their Calculation of TCNQ and Its Mono- and Di-valent Anion

ESR spectra of the anions of several aromatic heterocyclics, containing nitrogen, have been recorded with the object of correlating the observed nitrogen hyperfine splittings with the π‐electron spin‐density distributions.As a result of this analysis it is found that the 14N hfs splitting constant (AN) depends not only on the π spin density at the nitrogen site (ρNπ) but also on the π spin densities at the nearest‐neighbor carbon atoms (ρC1π and ρC2π, respectively).If, to a first approximation, the relationship is written as AN=QNNNρNπ+QCCN(ρC1π+ρC2π), where C1 and C2 are the two nearest neighbors of N, the coupling factors QNNN and QCCN are found to be +19.1±1.7 and +9.1±1.7 G, respectively.

14N Hyperfine Structure in ESR Spectra of Heterocyclic Anions

4 – Electron Spin Resonance of Porphyrin π Cations and Anions

Electron spin resonance (E.S.R.) spectra have been obtained from several semiquinones in strongly acidic media, where they exist as doubly protonated species. Hyperfine splitting was observed both from these protons and from the aromatic ring protons. Splitting constants are tabulated for the semiquinones obtained by the reduction of: 2 : 5-dihydroxy-p-benzoquinone, 1 : 4-naphthoquinone, anthraquinone, pyrazine, 4 : 4′-dipyridyl and phenazine. The quantitative features of these spectra can be reasonably interpreted in terms of simple molecular orbital theory.

Electron Spin Resonance Studies of the Diazine Negative Ions

Citations

ESR Study of Polyazine Anions

The UV Spectra and Their Calculation of TCNQ and Its Mono- and Di-valent Anion

14N Hyperfine Structure in ESR Spectra of Heterocyclic Anions

4 – Electron Spin Resonance of Porphyrin π Cations and Anions

Electron spin resonance studies of semiquinones and related nitrogen heterocyclic molecules in acid solution

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Self-consistent field theory of the electron spin distribution in π-electron radicals