Vibrational characterization of azobenzenes, azoxybenzenes and azoaromatic and azoxyaromatic polyethers

Raman and infrared spectra of a bisphenol-A-containing azoaromatic polyether, a bisphenol-A-containing azoxyaromatic polyether and a bisphenol-A-containing 2-hydroxyazoaromatic polyether were analyzed. Vibrational spectra were also collected for the corresponding model compounds 4,4′-(4-tert-butylphenoxy)azobenzene, 4,4′-(4-tert-butylphenoxy)azoxybenzene and 4,4′-(4-tert-butylphenoxy)-2-hydroxyazobenzene. Comparisons with substituted azobenzenes and azoxybenzenes were used in assigning the spectra in the 1650–900 cm-1 region. Assignments of the N=N stretch (1410–1390 cm-1) demonstrate that all of the compounds are in the trans configuration. The azo bridge vibrations of the azoaromatic ethers are very similar to those of azobenzene. Different types of hydrogen bonding are seen in the 2-hydroxyazoaromatic compounds. The polyether has an OH stretch at 3355 cm-1 which indicates a network of intermolecular hydrogen bonds among the polymers. The 2-hydroxyazoaromatic model compound has no IR peak above 3100 cm-1 and N=N, CO and CN stretches which are shifted due to an intramolecular hydrogen bond with the azo nitrogen. The N=N stretch of the azoxyaromatic ethers is at the same wavenumber as in the azo compounds. Assignment of the N→O stretch vibration is difficult because of mixing with other modes of the azoxy bridge. © 1997 John Wiley & Sons, Ltd.