| Abstrakt: |
Incorporation of aromatic amines, including diphenylamine (DPA), carbazole (Cbz), diphenylbenzidine (DPB) and benzidine (Bzd), into acid zeolites generated the corresponding radical cations, DPA•+, Cbz•+, DPB•+ and Bzd•+, as indicated by comparison of the characteristic long-wavelength diffuse reflectance spectra with spectra observed in solution. Samples of DPA•+ sequestered in HZSM-5 are deprotonated; the resulting diphenylaminyl radical, DPN•, is remarkably stable; diffuse reflectance or EPR spectra show that a significant population persists for longer than four years. In contrast, DPA•+ adsorbed within HY zeolite, undergoes a clean conversion to Cbz•+. Non-acidic zeolites devoid of Brønsted and Lewis sites failed to generate radical cations to an extent detectable spectroscopically; these results clearly indicate that Brønsted and/or Lewis sites are responsible for the observed oxidation. |
