Photographic Cyanine Dyes

An illustration of the technological significance of the relaxation phenomenon can be taken from photographic chemistry. Dyes of the cyanine class where Y = S, 0, CH—CH— n = 0,1,2,3...X = haUde, etc, are used as spectral sensitizers to extend photochemical response of the photographic silver hahdes, which only absorb blue and ultraviolet light, into the visible spectral regime. 

More recent research provides reversible oxidation-reduction potential data (17). These allow the derivation of better stmcture-activity relationships in both photographic sensitization and other systems where electron-transfer sensitizers are important (see Dyes, sensitizing). Data for an extensive series of cyanine dyes are pubflshed, as obtained by second harmonic a-c voltammetry (17). A recent "quantitative stmcture-activity relationship" (QSAR) (34) shows that Brooker deviations for the heterocycHc nuclei (discussed above) can provide estimates of the oxidation potentials within 0.05 V. An oxidation potential plus a dye s absorption energy provide reduction potential estimates. Different regression equations were used for dyes with one-, three-, five-methine carbons in the chromophore. Also noted in Ref. 34 are previous correlations relating Brooker deviations for many heterocycHc nuclei to the piC (for protonation/decolorization) for carbocyanine dyes the piC is thus inversely related to oxidation potential values. 

The nonreactive base structures of cyanine dyes (or carbocyanines) have been used for many years as components in photographic emulsions to increase the range and sensitivity of film and also in CD-R and DVD-R optical disks to record digital information. A major innovation came when Ernst et al. (1989) and Waggoner et al. (1993) recognized that cyanine dyes would make excellent labels for fluorescence detection, and for this reason, they synthesized reactive dye derivatives, which then could be covalently attached to proteins and other molecules. 

In recent years visible photoinitiators for the formation of polymers via a radical chain reaction have also been developed. These absorb light which is blue, green, or red and also cause the polymerization of polyolacrylates, in some instances, such as encapsulated systems, with speed which is near photographic. Some of these photoinitiators provide the photochemical backbone of the nonsilver, near-photographic speed, imaging processes such as the Cycolor processes invented by the Mead Corporation. Cycolor initiators are cyanine dye, borate ion salts (4)—so-called ( +, —) ion pair... 

The sulfones of 4-benzo[6]thienyl-ZV-methylcarbamate and its 2,3-dihydro derivative possess insecticidal activity.610 Several mero-cyanine dyes have been prepared from thioindoxyl-1,1-dioxide,735 736 and a number of 2-arylbenzo[6]thiophene-l, 1-dioxides are fluorescent and are useful commercially (e.g., as dyes 737 and in photographic films738). 2-(p-Isocyanatophenyl)benzo[6]thiophene-l, 1-dioxide has been incorporated in copolymers of use in the printing industry-302... 

J. R. Lenhard, A New Method for Measuring Electrochemical Potentials of Cyanine Dyes, in "Preprints The International East-West Symposium on the Factors Influencing Photographic Sensitivity (Oct. 28-Nov. 2, 1984, Maui,... 

Cyanine dyes were shown by Moore to act as sensitizers for visible light induced vinyl polymerization when used in combination with polyhalogen containing hydrocarbons (99). The dyes claimed are those which are known as effective sensitizers for silver halide photographic processes in which electron injection... 

Krause in the 1930 s proposed that the chromophore of rhodopsin was similar chemically to the polymethine compounds known as cyanine dyes which are also used to sensitize photographic emulsions to the longer wavelengths of the visible spectrum. He proposed that the chromophore was bound to a very large lipid/protein complex with a molecular weight near 800,000. 

Dyes having similar constitutions (e.g., 625) are claimed to improve spectral sensitivity in classical photography (88JAP63/110444). Other cyanine dyes (509, 512, 607) have already been described (Sections IV,A,5,e IV,A,5,f IV,B,3,c). It has also been reported that fused tropylium salts such as 224-type compounds stabilize photographic emulsions (90JAP02/ 156240). 

Some benzodipyrroles, furans, and thiophenes with quinonoid structures have been patented as dyes <90EUP363034>, and some thienobenzothiazoles have potential in cyanine dyes for photographic uses <84URP1082786>. 

The introduction of the nitro group in azoles leads to a long-wave shift of the visible absorption maximum and an enhancement of the sensitizing properties of cyanine dyes. A long-wave shift of the sensitivity of photographic materials is... 

Cyanine dyes in this series have been described as photographic sensitizers, and are strongly adsorbed on the silver bromide crystals. The sensitization maximum is at about 500-650 m/x.83... 

A spirothietane sulfone-oxetane is a comonomer in the preparation of polyethers. A polymer obtained from this sulfone in a solution of bis(3,3-chloromethyl) oxetane with phosphorus pentafluoride can be spun to drawable filaments. Thietane sulfone spirocyclic carbonates may be polymerized via the carbonate group to high-molecular-weight solids said to be useful in laminating. Thietane 1,1-dioxide improves the dye receptivity of poly (acrylonitrile), viscose, cellulose acetate, and poly(vinyl chloride). It is also reported to be a stabilizer for nitric acid in oxidizer mixtures for rocket motors. 2-Methylthietane 1,1-dioxide is claimed to be superior to sulfolane (thiolane 1,1-dioxide) in the liquid extraction of aromatic hydrocarbons from mixtures with saturated hydrocarbons. " A number of bis(3,3-alkoxy) thietane 1,1-dioxides have been proposed as intermediates in the preparation of cyanine dyes useful as photographic sensitizers. " ... 

Thietanone 1,1-dioxides are intermediates in the synthesis of cyanine dyes used as photographic sensitizers. ... 

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