Extended conjugation in di- and tri-arylmethanes. Part III. Electronic absorption spectra of transversely conjugated naphthalene analogues of Crystal Violet, Malachite Green, and Michler's hydrol blue

Abstract

Spectral changes caused by the effect of the additional ring in transversely conjugated naphthalene analogues of Crystal Violet, Malachite Green, and Michler's Hydrol Blue are described and discussed. Although peri-hindrance of the terminal dimethylamino-groups leads to incomplete conversion of dye base into dye in acid solution, and to ready protonation of the crowded groups, the univalent cations are shown to be electronically symmetrical and pronounced bathochromic shifts of the first bands are observed. The carbonyl group of bis-(4-dimethylamino-1-naphthyl) ketone is unusually resistant to reduction.