p-Phenylazoaniline hydrochloride from powder data: protonation site and UV-visible spectra

The crystal structure of the title compound, (4-aminophenyl)phenyldiazenium chloride, C12H12N3+. Cl-, was determined from X-ray laboratory powder data , and the protonation on the azo group was confirmed by the neutron powder data. The cations form stacks along [100], while the chloride anions form h ydrogen bonds to all three H atoms attached to N atoms. The absorption maxi mum of the crystalline salt is shifted bathochromically by 850 cm(-1), comp ared with that in ethanol solution.