Resonance-stabilized phenylazo-ene-phenylimine cations of cyclobutanetetraone derivatives Original Research Article

Cyclobutenedione phenylazo-phenylamines were found to exhibit bathochromic shifts in acidic media and hypsochromic shifts in basic media, like phenylazo-phenylhydrazones. The bathochromic shifts are due to the formation of resonance-stabilized cations and the hypsochromic shifts to enolization. The phenylazo-phenylamines and their cations and anions have been studied by NMR spectroscopy.