Cyanine

Cyanines ( gr cyanos, κυανός, blue) or cyanine dyes is a collective term for synthetic organic dyes from the group of polymethine dyes. These were systematized in 1922 by Walter King. Cyanine all have both a quaternary ammonium group as an electron acceptor ( Antiauxochrom ), and a tertiary amino group as an electron donor ( auxochrome ), which are connected via a polyene bridge. Cyanines are thus becoming increasingly imines ( azomethine ). Both groups have a relatively strong bathochromic effect, which is why cyanine dyes already absorb light in the visible range with a very small π - electron systems.

The cyanines consist of the diarylmethane, triaryl methane and quinone.

Structure

The cyanines can be divided into three sub-groups:

  • The structure of the streptocyanines or open-chain cyanines is
  • , The quaternary nitrogen - atom component of a heterocyclic ring system, it is called hemicyanine:
  • The second nitrogen atom is part of a ring, it is a cyanine geschlossenkettiges:

The chain links between the two nitrogen atoms are usually present in the more stable all- trans form. Frequently, derivatives of nitrogen-containing heterocycles, such as quinolines, thiazoles, pyrroles, imidazoles, oxazoles, or be used, in which one or both nitrogen atoms are part of a ring system. The heterocyclic dye compound can thus be either a hemicyanine (type II), or a geschlossenkettiges cyanine (type III).

Production

Cyanine dyes can be prepared by various methods, including by the condensation of aldehydes with amines complex.

Frequent cyanine

Properties and Uses

Most cyanines are colored blue and light sensitive, so only have a low color fastness and are not generally used for dyeing of textiles. The light sensitivity makes them ideal for use in photography, where they are used to raise awareness of the photographic emulsion. Even in organic dye lasers as well as a drug against worm infections Cyanine be used. Brooker's merocyanine is used as a solvatochromic indicator.

CD / DVD dye

Cyanines were used to produce the first CD-R and are still partially ( approximately by Taiyo Yuden ) in use, as in the Orange Book specifies. Since cyanine is chemically unstable, various mixtures (metal- stabilized cyanine TDK, Super Cyanine by Taiyo Yuden ) have been developed which are durability moderate the azo and phthalocyanine media equal. Cyanine CD-R is patented by Taiyo Yuden. Cyanine include azo dyes as well as to the long strategy dyes. For the cyanine type numbers 0-4 are reserved for CD -R. Today's DVD -R media using mixtures of cyanines and azo dyes.

Biochemistry

Proteins may be stained with, inter alia, the triarylmethane dye Coomassie Brilliant Blue or Fast Green FCF merocyanines, SYPRO Orange, or SYPRO Red for a SDS-PAGE. The asymmetric cyanine dye SYBR Green I is used for the detection of double-stranded DNA. The triaryl fuchsin and parafuchsine be used for staining in histology. Various cyanines can be used to label the molecule.

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