Xanthenes, Acridines and Oxazines

These classes of chemicals contain not only some of the oldest dyes, dating back to the 19th centnry, bnt also some of the most important flnorescent chromophores. The earliest of these discoveries was flnorescein (3.21), which was later brominated to give the polybromo derivative eosin (3.22) (Fignre 3.10). They are of little importance in textile coloration processes bnt are nsed in some fluorescent pigments and extensively in analysis and biological methods and also in tracing the course of water in drains and other water outlets. 

The nitrogen analogues of the rhodamines based on acridine (3.24) are strongly 

Derivatives of long established fluorescent dyes based on the phenoxazine ring system, such as the cationic Nile Blue (3.25a) 627 nm, and the neutral Nile Red 

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