Principal Properties and Classification

The general synthesis of the most important dyes within this group, e.g. the cyanine dyes, is described in Section 5.7. 

A cyanine containing three carbon atoms between the heterocyclic rings is called a carbocyanine (3, n = 1). Replacing these carbon atoms by one, two, and three nitrogen atoms produces aza-, diaza-, and triazacarbocyanines. Dyes of these three classes are important yellow dyes for polyacrylonitrile, e.g., C.I. Basic Yellow 28, 48054 [54060-92-3] (4) 

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