Triarylmethane dyes are synthetic organic compounds containing triphenylmethane backbones.
Variation is found is dimethylamine vs diethylamino substituents on the phenyl rings and variations of the secondary amine on the naphthyl group.
Where two of the aryl groups are bridged by a heteroatom, these triarylmethane compounds may be further categorized into acridines (nitrogen-bridged), xanthenes (oxygen-bridged), and thioxanthenes (sulfur-bridged).
The amine-containing dyes are often prepared from Michler's ketone or its diethylamino analogue.
The Friedel–Crafts alkylation reaction is a popular method to prepare many of the phenolic derivatives: In addition to their dominant use as dyes, many of these dyes react reversibly with acid and base, and thus serve as pH indicators.