M. Ballester et al., SYNTHESES AND SPECTRA OF SOME INERT TRIPHENYLMETHYL DIRADICALS - A CONCURRENT DIRADICAL FORM, Journal of the American Chemical Society, 116(10), 1994, pp. 4205-4210
The synthesis and characterization of 11 inert diradicals of the perch
lorotriphenylmethyl class, -6-Cl-4(C6Cl5)C-C6Cl4-Sp-C6Cl4-C(C6Cl5)-C6C
l4-R(p) where R is Cl, OH, or O- and Sp is a spacer chain from zero to
nine atom links, are described. The ESR spectra of these species in s
olution from room temperature to -140 degrees C (glassy matrix) point
to the concurrence of two isomeric diradical forms: the conventional s
pecies, displaying spin-spin dipolar interaction, and a form apparentl
y devoid of it. The ESR C-13 hyperfine couplings, the magnetic suscept
ibility, and the IR and UV-vis spectra of these diradicals are describ
ed. Some related monoradicals and a triradical are also reported.