Generation and conversions of aromatic amine radical cations in acid zeolites

Incorporation of aromatic amines, including diphenylamine (DPA), carbazole (Cbz), diphenylbenzidine (DPB) and benzidine (Bzd), into acid zeolites gene rated the corresponding radical cations, and DPA(.+,) Cbz(.+), DPB.+ and Bz d(.+), as indicated by comparison of the characteristic long-wavelength dif fuse reflectance spectra with spectra observed in solution. Samples of DPA( .+) sequestered in HZSM-5 are deprotonated; the resulting diphenylaminyl ra dical, DPN.+ is remarkably stable; diffuse reflectance or EPR spectra show that a significant, population persists for longer than four years. In cont rast, DPA(.+) adsorbed within HY zeolite, undergoes a clean conversion to C bz(.+). Non-acidic zeolites devoid of Bronsted and Lewis sites failed to ge nerate radical cations to an extent detectable spectroscopically; these res ults clearly indicate that Bronsted and/or Lewis sites are responsible for the observed oxidation.