Structure
There are three types of cyanines:
- Streptocyanines or open chain cyanines:
- R2N+=CHn-NR2 (I)
- Hemicyanines:
- Aryl=N+=CHn-NR2 (II)
- Closed chain cyanines:
- Aryl=N+=CHn-N=Aryl (III)
where two nitrogens are joined by a polymethine chain. Both nitrogens are each independently part of a heteroaromatic moiety, such as pyrrole, imidazole, thiazole, pyridine, quinoline, indole, benzothiazole, etc.
Read more about this topic: Cyanine
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