Cyanine dyes, formation

Even if the specific role attributed to benzothiazolium was not confirmed later (24), all these syntheses account for the significant and common behavior of quaternary salts, carbocations giving either symmetrical or asymmetrical reactive anhydrobases. They constitute the mam step in cyanine dye formation. 

Arylation—The only important case is that of cyanine dye formation. This has been mentioned under the heading of substituted alkylation by replacement of halogen in a quaternary pyridinium salt. The relevant case here is the complementary one in which a picoline quaternary salt reacts with a halogen-substituted heterocyclic quaternary salt (p. 205). Both 2- and 4-picolinium salts have been used satisfactorily in such reactionsi fr... 

Anhydro bases can attack the a-position, e.g. of thiazolium cations, with the formation of adducts capable of oxidation to cyanine dyes, e.g. Scheme 18 (see Section 4.02.3.3.4). 

Sensitivity of the proposed method correlates with molai absorptivity of the cyanine dye. Mixed POMs PMeMo O j (Me=TP+, Sb +, BP+) were chosen as analytical form because of its higher stability as compared with 12-molybdophosphate. Only 2-3T0 concentration of molybdate is enough for complete formation of POM avoiding in this way formation of lA with polymolybdate ions. In addition, mixed POMs are stable in wider interval of pH. Increasing of anion chai ge from 3 to 5(6) is also favorable. Constant absorbance of lA is observed in the acidity range of 0.12-0.28 M. 

Electrophilic substitution, e.g. of the 2-position of the indole ring, followed by the elimination of water leads to the formation of cyanin dyes from ergot alkaloids [53]. 

Wang M, Silva GL, Armitage B (2000) DNA-templated formation of a helical cyanine dye J-aggregate. J Am Chem Soc 122 9977-9986... 

Ogul chansky TYu, Losytskyy MYu, Kovalska VB, Lukashov SS, Yashchuk VM, Yarmoluk SM (2001) Interaction of cyanine dyes with nucleic acids. XVIII. Formation of the carbocya-nine dye J-aggregates in nucleic acid grooves. Spectrochim Acta A Mol Biomol Spectrosc 57 2705-2715... 

Cyanine dye-CD complexes were first reported by Kasatani et al. in 1984 using 3,3 -diethyloxadicarbocyanine iodide (DODC) [22]. It was found that this dye formed complexes with (3- and y-CDs but not with a-CD. Later, they demonstrated the same tendency with cyanines 1 and 2 [23]. It was shown that inclusion of cyanine dyes in [i-CD and Me-(3-CD helps to inhibit dimer formation as well as to enhance the photostability of these cyanines, thereby enhancing the dyes utility as a fluorescent probe [7, 24],... 

Gadde S, Batchelor EK, Kaifer AE (2009) Controlling the formation of cyanine dye H- and J-aggregates with cucurbituril hosts in the presence of anionic polyelectrolytes. Chem Eur J 15 6025-6031... 

An interesting equilibrium study was performed by Kasatani and coworkers on the interaction of a series of cyanine dyes with beta and gamma cyclodextrin, using u.v.-visible spectrophotometric measurements. The results were consistent with the enhancement of dimer formation by inclusion of the dye molecules within the cyclodextrin. As expected from the work of others, such geometrical factors " as the size of the aromatic groups and the lengths of the central methine chains strongly influence the occurrence of dimer formation within the cyclodextrin cavity. 

Linear-dichroic spectra of SA monolayers prepared from mixtures of OTS and a cyanine-dye surfactant established the absence of dimerization and the orientation of the chromophore parallel to the substrate [183]. In contrast, the same cyanine dye underwent sandwich-type dimer formation in LB films and had its chromophore oriented perpendicular to the water surface [192]. These results highlight an important difference between LB and SA monolayers. Parameters which determine monolayer formation on an aqueous subphase are also responsible for the orientation and organization of the surfactants therein. Furthermore, the configuration of the surfactants is retained regardless of the structure of the substrate to which the floating monolayer was subsequently transferred to by the LB technique. Conversely, in SA monolayers, surfactant organization is primarily dependent upon the nature of the substrate [183]. 

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... 

Aryliodonium salts have been found to be coinitiators for photooxidizable dye sensitization (105). Smith polymerized aerylamide-bis(acrylamide) mixtures using acridine, xanthene, or cyanine dyes and, for example, diphenyllodonium chloride as an electron acceptor. Reduction of the salt results in the formation of phenyl radicals. 

Squarylium dyes such as (83) [75] have probably received less attention than cyanine dyes due to the fact that the majority of syntheses furnish symmetrical species which are difficult to monofunctionalize in reactions such as the formation of peptide conjugates. The unsymmetrical types have been reported but seem to suffer from about 50% decrease in extinction coefficient. Squaiyliums are also more difficult to handle due to their low solubility. Very few water-soluble systems have been reported. These compounds are also used exclusively as fluorophores, but quantum yields are highly dependent on substituents and environment. 

Effect of Aggregate Formation upon Electronic Energy Levels of Cyanine Dyes... 

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