A Paramagnetic Resonance Study of Unhindered Biphenyl Anion Radicals (III)

Abstract

The radical anions of biphenyl and some of its bridged derivatives have been studied by e.s.r. It is found that the proton hyperfine coupling constants change monotonically through the series of radical anions derived from biphenyl, 9,lO-dihydrophenanthrene, fluorene, dibenzothiophene, and dibenzofuran. Deuterations have been carried out for the latter two compounds and the hyperline coupling constants are assigned to specific positions in these anions. The data are displayed in the form of a correlation diagram from which assignments for other bridged biphenyl anions can be made.Les anions radicalaires du biphCny1 et des dCrivCs pontes ont Ct C Ctudits par r.p.e. I1 a Ct C trouve que les Ccarts hyperfins de protons changent graduellement dans la sCrie des anions radicalaires derives du biphenyl, 9,lO-dihydrophenanthrene, fluortne, dibenzothiophene et du dibenzofuranne. Des deutkrations ont ete effectukes pour les deux derniers composCs et les Ccarts hyperfins ont ete assignes a des positions specifiques pour ces anions.Les resultats sont reprCsentCs sous forme de diagramme de corrClation au moyen duquel des valeurs de couplages d'autres anions hyperfins pontts peuvent &re obtenues.Canadian Journal of Chemistry, 49, 3529 (1971) IntroductionIn previous papers in this series (1,2) the spectra of hindered diarylmethyl radicals were obtained and some insight was gained into the internal configuration of such molecules from a study of the proton hyperfine structure. The ideas behind this work have been extended to the biphenyl series of compounds. It has been suggested that biphenyl itself is not planar, and that steric interactions between the ortho protons prevent the two rings from assuming a perfectly coplanar arrangement. The results of gas phase electron diffraction studies suggest the rings are oriented at an angle of 42" to each other (3) while X-ray studies on the crystal suggest the rings are coplanar, but are connected by a rather long bond (for an aromatic)

An Electron Spin Resonance Study of the 9,10-Dihydrophenanthrene Radical Anion

“…Finally the two small splittings can be assigned by comparison to u.H.f.-s.c.f. results (8) or by use of a valence bond superposition method (9), and by analogy to other diphenyl compounds that have been deuterated or methylated in these positions (9,10). Thus an assignment of a, = a, = 0.70 oe and a, = a, = 0.15 oe is consistent with all available data from other sources.…”

Electron spin resonance

“…76), substituted cyclooctatetraenes (131), substituted triptycenes (44,48,85,169), substituted phenyl silanes (37, 43. 89, 129, 147, 182, 196), symmetrically disubstituted biphenyls (4,80,116,158,175), symmetrically disubstituted diphenylmethanes (146,176), naphthalenes (35,59,64,86), azulenes (77,139), biphenylene (38), 9,9'-disubstituted anthracenes (157), anthrasemiquinone (29. 190), 9,9-diphenylanthrone (121), 10-phenylacridine (102), rubrene (20), and pyrene (33,160).…”