page_title: Cyanine
section_title: Structure
hierarchical_section_title: Cyanine / Structure
caption_attribution_description: Chemical structure of Cyanines
context_page_description: Cyanines are defined as "synthetic dyes with the general formula R2N[CH=CH]nCH=N+R2↔R2N+=CH[CH=CH]nNR2 in which the nitrogen and part of the conjugated chain usually form part of a heterocyclic system, such as imidazole, pyridine, pyrrole, quinoline and thiazole." Cyanines are used in industry biotechnology.
context_section_description: Cyanines have been classified in many ways:
  Streptocyanines or open chain cyanines:
  R₂N⁺=CH[CH=CH]ₙ-NR₂ (I)
  Hemicyanines:
  Aryl=N⁺=CH[CH=CH]ₙ-NR₂ (II)
  Closed chain cyanines:
  Aryl=N⁺=CH[CH=CH]ₙ-N=Aryl (III)
  Additionally, these classes are recognized:
  Neutrocyanines:
  R₂N⁺=CH[CH=CH]ₙ-CN and  R₂N⁺=CH[CH=CH]ₙ-CHO
  Merocyanines including spiropyrans and quinophthalones.
  Apocyanines
  where two quaternary nitrogens are joined by a polymethine chain. Both nitrogens may each be independently part of a heteroaromatic moiety, such as pyrrole, imidazole, thiazole, pyridine, quinoline, indole, benzothiazole, etc.
caption: The Cyanines:
  I = Streptocyanines,
  II = Hemicyanines,
  III = Closed cyanines
exif: {}