ESR, 1H, and 2D Studies of the Radical Anion of 1,3,5-Triphenylbenzene

MO calculations predict that the monoanion of 1,3,5‐triphenylbenzene (Tpb) is in an orbitally degenerate ground state. Nevertheless, the ESR spectrum in liquid NH₃ is well resolved; the derivative linewidth is equal to 0.06 Oe only. The $g$ value and the electronic relaxation times $T_1$ and $T_2$ were comparable in magnitude to those of orbitally nondegenerate radicals. It is suggested that twisting of the phenyl rings out of the plane of the molecule, which may lift the orbital degeneracy, is the principal reason of this behavior. ¹H and ²D NMR experiments were performed on a reduced sample of Tpb, containing both normal and perdeutero‐Tpb. From the Fermi contact shifts signs and magnitudes of all hyperfine splitting constants have been determined, and they agreed very well with the ESR splitting constants. From the proton linewidths the electronic and dipolar correlation times were inferred. Quadrupole coupling constants for all deuterium nuclei were calculated from the ²D linewidths.