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Das Redoxverhalten der bromsubstituierten Triarylamine 2 -7 wurde mit Hilfe der Methode der cyclischen Voltammetrie untersucht. Die Oxidationspotentiale des Redoxpaars Amin/ Radikalkation hangen stark vom Substitutionsgrad in den ortho-Positionen ab, wobei zusatzlich zu einem starken elektronischen Effekt ein schwacherer sterischer EinfluB beobachtet wird. Der Einflua der Substitution auf das zweite Oxidationspotential, RadikalkatiodDikation, ist wesentlich geringer. Die UV/VIS-Spektren der zugehorigen Radikalkationen sind mit zunehmender ortho-Substitution bathochrom verschoben. Zwischen Redoxpotential der Amine und langwelligstem Absorptionsmaximum der Radikalkationen besteht ein hearer Zusammenhang. Redoxpotentiale und UV/VIS-Spektren gestatten eine partielle Termanalyse der Amine und der zugehorigen Radikalkationen. Die ESR-Spektren der Radikalkationen zeigen breite unaufgeloste Signale. Organic Electron Transfer Agents, I Electrochemical and Spectroscopical Study of Bromo-substituted Triarylamine Redox SystemsThe redox behaviour of the bromo-substituted triarylamines 2 -7 has been studied by cyclic voltammetry. The oxidation potentials of the redox pair amine/cation radical strongly depend on the degree of substitution in ortho-position showing a smaller sterical influence in addition to a strong electronic effect. The second oxidation potential, cation radical/dication, is influenced by substitution to a much smaller degree. The UV/VIS spectra of the corresponding cation radicals are shifted bathochromically with increasing ortho-substitution. A linear relationship between redox potentials of the amines and long wave-length absorbance maxima of the cation radicals is observed. Redox potentials and UV/VIS spectra allow partial analysis of the term schemes of the amines and the corresponding cation radicals. ESR spectra of the cation radicals show broad and unresolved signals.

Articles you may be interested inPhotoelectron spectra of polynuclear aromatics. V. Correlations with ultraviolet absorption spectra in the catacondensed seriesThe high-resolution photoelectron spectra of 65 polycyclic aromatic hydrocarbons containing up to II condensed benzene rings have been obtained in the gas phase at temperatures between 20 and 450"C. Vibrational analysis of the spectra coupled with semiempirical MO calculations permitted positive identification of the 71' ionizations in the 6-11 eV range. Irrespective of size and symmetry of the hydrocarbons, two-thirds of all 71' bands are found to precede the onset of (T ionization, which occurs at 1O.6±0.2 eV in the molecules beyond naphthalene. The possibility of lahn-Teller forces operating in the degenerate ionic ground states of D 3h and D 6h molecules is discussed, and comments are made on the origin of the 1350 cm -\ vibrational progression that prevails in the first band of all planar hydrocarbons. In sterically overcrowded systems, excitation of low-frequency twisting and out-of-plane bending modes results in a blurring of the vibrational structure. In cases where reliable x-ray data are unavailable (e.g., dibiphenylene-ethylene), this observation allows a distinction to be made between planar and nonplanar hydrocarbons. The present data are of sufficiently high quality to permit the question as to the planarity of phenanthrene to be settled with some certainty. 12 14 FIG. 4. The photoelectron spectrum of peropyrene (286°).

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