Aerial Oxidation of Protonated Aromatic Amines. Isolation, X?ray Structure, and Redox and Spectral Characteristics of N- Containing Dyes

摘要

This work reports the results of our investigation on thenaerial oxidation of aromatic amines that are promoted by protic acid. Whilenprimary aromatic amines produce substituted phenazines as majornproducts, N-phenyl-o-phenylenediamine produces polycyclic aromaticnheterocycles like azaacene and secondary and tertiary amines givenexclusively the dyes containing a triphenylmethane moiety. Isolation ofnthe compounds and the effects of substitutions on the aromatic rings havenbeen investigated. In this context, plausible reaction steps that are involvednhave been discussed. Single-crystal X-ray structure analyses of thenrepresentative compounds are solved to authenticate their formation. Innalmost every case, a high degree of delocalization of electron was noted.nThe compounds have been characterized thoroughly and show richnspectral properties. For example, the phenazine molecules exhibitednabsorption peaks between 475 and 605 nm because of the charge-transferntransition from the amine and tricyclopyrazine moiety. Their acidochromic and solvatochromic behaviors, which are supportednby theoretical calculations, are investigated. The polycyclic azacene molecule exhibits strong absorption in the visible region andnfluoresces with high quantum yield. The phenazine dyes undergo a quasi-reversible reduction at a low cathodic potential thatnvaries linearly as a function of Hammett’s constant.