Anisotropic electrical conductivity and e.s.r. spectra of a whisker prepared by electrolysis of 3,3′,5,5′-tetramethylbenzidine

The electrical conductivity of a whisker prepared by electrochemical oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) was investigated. The TMB whisker showed significant anisotropic conductivity: the conductivity parallel to the long axis of the whisker showed a high value (σ = 1.03 S/cm), whereas the perpendicular one showed a low value (σ = 5.11 × 10^-4 S/cm). The cation radical salt of TMB prepared by chemical oxidation with I₂ showed low conductivity (σ = 2.57 × 10^-4 S/cm) because of the amorphous structure. The association of TMB cation radicals in the whisker was suggested by absorption spectra and e.s.r. spectra of the whisker dissolved in organic solvents. The e.s.r. specturm of a TMB whisker showed anisotropy because of the crystalline structure, whereas the e.s.r. spectrum of the chemical oxidation product was a singlet symmetrical signal which is typical of an amorphous structure. The e.s.r. signal of the whisker showed a rapid intensity drop with decreasing temperature, in comparison with that of the chemical oxidation product.