Extended conjugation in di- and tri-arylmethanes. Part II. Electronic absorption spectra of longitudinally conjugated naphthalene analogues of Crystal Violet, Malachite Green, and Michler's Hydrol Blue

Abstract

Spectral studies show that terminal nitrogen atoms attached to longitudinally conjugated naphthalene groups in analogues of Crystal Violet, Malachite Green, and Michler's Hydrol Blue have a greater tendency to conjugate with the central carbon atom than those in the corresponding 9,9-dimethylfluorene analogues. Conjugation is most effective in the Crystal Violet analogue (II; R = NMe₂) in which a high resonance-energy counterbalances the high energy of the quinonoid naphthalene group.