Cyanine-type dyes

Selenazoles and their derivatives, that is. selenazolines and selenazo-lidines. aremainh used in cyanine-type dyes and photographic sensitizers as well as in pharmacology and chemotheraphs. 

Methyl- and 4-methyl-pyridinium methiodides yield cyanine-type dyes with chloroform and alcohohc potassium hydroxide, e.g. via the methylene dihydropyridine (51) with attack by dichlorocarbene at the active methylene group (cf. ref. 92a). 

Figure 9.44 The common nitrogenous ring structures of cyanine-type dyes. Indolium-based dye derivatives are the most frequently used due to the high extinction coefficient of the indol groups.

Because of a perceived importance of amino substituents for biological activities in 1,8-naphthyridines, e.g.,359 422 478 526 1395,1410 sucjj derivatives have been widely investigated, for example, with respect to their ionization,1043 NMR spectra,174 mass spectra, fluorescence properties, tautomerism, and conversion into cyanine-type dyes.768... 

The reaction of 4-methylthioquinolizinium salt with 1,4-dimethylquinoli-nium salt in the presence of piperidine gave a reddish-purple cyanine dye 321 (41%) (54JOC499). Cyanine-type dyes were also obtained by the... 

Condensed aromatic compounds (benzoselenazoles) are considered much more stable, and they are in fact more commonly used in the area of cyanine-type photographic dyes. 

Selenium and selenium compounds are also used in electroless nickel-plating baths, delayed-action blasting caps, lithium batteries, xeroradiography, cyanine- and noncyanine-type dyes, thin-film field effect transistors (FET), thin-film lasers, and fire-resistant functional fluids in aeronautics (see... 

It should be stressed here that the conductivities of e.g. polymers with phthalo-cyanine-type structure vary between 6.3 x 10 3 and 2.1 x 10 10 1 1 with activation energies down to 0.04 eV 8,68,69) The best conducting dye polymers showed a maximum of . 

The well-known indicator phenolphthalein (8) is an example of tri-arylmethane dyes which represents a cyanine-type chromogen and does not fluoresce. If an oxygen bridge is introduced between the upper benzene rings, the intensely green fluorescing flourescein (1) results. 

An electrode covered with several molecular layers of dye could be made to adsorb all of the visible light, and obviate the need for the multielectrode stack. Very thick dye layers have tended not to be conductive or highly photoconductive so that their photoelectrochemical efficiencies are no better and perhaps worse than those seen on electrodes modified with very thin dye films. Molecular disorder of the dye appears to be the dominant reason for lack of conductivity in thick films of fluorescein-type, cyanine-type, and phthalocyanine-type dyes (12). It has been shown however that ordered molecular systems (mainly conjugated, highly unsaturated hydrocarbons) have considerable potential as conductive media, and that these ordered systems may be used to chemically modify electrode surfaces (12, 15). 

Here we focus on the literature of photophysical processes and photochemical reactions of cyanine and merocyanine dyes in solution at ambient temperatures. Besides pioneering and fundamental articles, " mainly recent pubhcations are discussed. This chapter does not include stilbazolium-type dyes and their crown ethers, and data concerning films or adsorbed dyes - are not covered. 

For 12 and 13 type dyes with various counterions in nonpolar media, electron transfers via singlet and triplet states were distinguished by flash photolysis. The rate constant for electron transfer from the first excited singlet state of 02 in methanol to benzoquinone and other suitable acceptors is = (1-3) X 10 ° M secr. Electron transfer, involving the triplet state of T2-T4, was performed with benzoquinone and ascorbic acid in alcohols. ESR results with various cyanine dyes were interpreted by electron transfer involving the superoxide radical anion. Electron transfer competes with delayed fluorescence and trans—Kis isomerization when induced by energy transfer from triplet anthracene to 13 dyes. Charge-transfer states were reported for cyanine-oxonol ion pairs. 

Additional Chromophores. Other types of dyes that have been studied as chromophores in dye developers include rhodamine dyes, azamethine dyes, indophenol dyes, and naphthazarin dyes (21). Cyanine dyes, although not generally stable enough for use as image dyes, have also been incorporated in dye developers (31). 

Several examples of the chromophoric systems (A), (B), and (C) are shown ia Figure 1. The early dyes were single chromophore stmctures of the type (A) WiUiams cyanine [862-57-7] Piaacyanol [605-91-4], and thiacarbocyanine [905-97-5]. The more compHcated dye stmctures ia Figure 1 stUl contain these chromophoric systems. 

Several types of nitrogen substituents occur in known dye stmetures. The most useful are the acid-substituted alkyl N-substituents such as sulfopropyl, which provide desirable solubiUty and adsorption characteristics for practical cyanine and merocyanine sensitizers. Patents in this area are numerous. Other types of substituents include N-aryl groups, heterocycHc substituents, and complexes of dye bases with metal ions (iridium, platinum, zinc, copper, nickel). Heteroatom substituents directly bonded to nitrogen (N—O, N—NR2, N—OR) provide photochemically reactive dyes. 

Symmetrical, long-chain cyanine dyes for laser appHcations provide output from 680 to 980 nm (76). Although these dyes were obtained through early screening procedures, infrared dyes for other technologies use similar stmetures. A long-chain indolenine-type cyanine dye, general stmeture as in dye (34), has been described as the sensitizer in optical disk memories (77). 

Engchpedia articles oa specific chemical types of dyes ate Azinedyes Azo dyes Cyanine dyes Dyes, anthraquinone Phthalocyanine compounds POLYTffiTHINE dyes StILBENE DYES SULFURDYES ThIAZOLE DYES TrIPHENYLT THANE AND RELATED DYES XaNTTIENE DYES. 

Dyes, polymethine used for dyes having at least one electron donor and one electron acceptor group linked by methine groups or aza analogues aUopolar cyanine, dye bases, complex cyanine, hemicyanine, merocyanine, oxonol, streptocyanine, and styryl. Supersensitization has been reported for these types—18 cites for cyanines, 3 for merocyanine, and 6 for all other polymethine types. 

O Regan B, Schwartz DT (1995) Efficient photo-hole injection from adsorbed cyanine dyes into electrodeposited copper(I) thiocyanate thin films p-type semiconductors. Chem Mater 7 1349-1354... 

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