Electron spin resonance study of some polycyclic nitrogen heterocyclic radical anions

Sevenster, Arjen J. L.; Tabner, Brian J.

doi:10.1002/mrc.1270220810

Cited by 6 publications

(2 citation statements)

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“…Im ESR-Spektrum bei 260 K (Fig.2,a), welches um einen g-Faktor von 2,0031 zentriert ist, wird ein bei Radikal-Anionen von N-Heterocyclen haufig anzutreffendes Phanomen [20] beobachtet: Die Randlinien sind gegeniiber denen im Zentrum stark verbreitert. Ursache dieser selektiven Linienverbreiterung sind die bei tieferen Tempera- (1) und C (7).…”

Section: Srhemu Iunclassified

“…In den Ph-Substituenten sind die Spindichten deutlich kleiner und ihre Torsionswinkel w mussen in den HMOIMcLuchlun -Berechnungen ( I ) durch eine winkelabhangige Storung KC2,3Cph = K,, x cos odes Coulomb-Terms zwischen C(2) bzw. C (3) [20] ein: Der Torsionswinkel o = 0" erhoht deren Spindichten vor allem auf Kosten derjenigen in den C(5)-und C(8)-Stellungen erheblich. In allen drei Chinoxalin-Radikalanionen befindet sich etwa die Halfte des Gesamtspins an den N-Zentren.…”

Section: Srhemu Iunclassified

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Strukturen und Molekül‐Eigenschaften ladungsgestörter Moleküle. 52. Mitteilung. 2, 3‐Diphenylchinoxalin‐Radikalanionen in Lösung und im Kristall

Bock

John

Näther

et al. 1994

Helvetica Chimica Acta

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The Naa and K@ radical-ion salts of 2,3-diphenylquinoxaline seem to be (according to a structural database search) among the first ones of N-heterocyclic radical anions in crystals. The one-electron reduction in aprotic 1,2-dimethoxyethan (DME) solution at metal mirrors and the crystallization under Ar have been preceded by cyclovoltammetric (CV) and ESRiENDOR measurement. The first electron insertion at -1.63 V proves to be reversible, whereas the irreversible second step, which is accompanied by an overcrossing of the CV line, can be rationalized by an 'ECE-DISP' mechanism via a dianion redox disproportionation. The ENDOR spectrum resolves four 'H couplings and allows to simulate the ESR spectrum including the I4N hyperfine splittings. Both dark-blue single crystals of the radical ion salts [2,3-diphenylq~inoxaline'~ Met@(DME)]' show unexpected similarities for Met@ = Naa, K@ despite the 36-pm difference in their ionic radii. The largest structural changes inflicted by the one-electron reduction of the N-heterocyclic molecule are observed in the vicinity of the N-centers bearing the highest effective nuclear charge. The DME-chelated metal cations coordinate at the N electron pairs and form Met@(DME)-bridged polymer chains of the radical anion, which are differently ondulated in the Nae and KQ radical anion salts. The take-home lesson suggests that many more N-heterocyclic molecules might be analogously reduced under optimized conditions and isolated as single crystals.

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Section: Srhemu Iunclassified