Cyanin chloride

Jelley EE. 1937. Molecular, nematic and crystal states of l,l -diethyl- /-cyanine chloride. Nature 139 631-632. 

As noted, the uniformity of the detector used to make absorption measurement and whether it is energy-based or Figure 5.3.5-2 CR Absorption spectmm of aqueous quantum-flux based should be determined. A major solutions of diethyl-2,2 -cyanine chloride at 25C (1) 1.3 x problem has occurred in psychophysically determiningthe 5M 1-3 x 10 3M (3)7.1 x 10 3M (4) 1.4 x 10... 

Anthocyanins cyanidin chloride, callistephin chloride, pelargonin chloride, ideanin chloride, cyanin chloride and pelargonidin chloride (Prof. Liselotte Krenn, Vienna, Austria) were dissolved in DMSO. 

Akins " reported an enhancement of about 2000 for cyanine chloride when adsorbed on a silver sol. However, the dye absorption is centered around 530 nm, while for the Raman studies a 564-nm excitation was used, i.e., a slightly off-resonance situation. An absorption feature, not present for the dye by itself or the sol alone, was seen at about 575 nm. Akins interprets it as due to a dye aggregate. However, as will be seen in Section II.5, similar bands are commonplace in SERS systems. In a separate study, Li et alP tried to evaluate the enhancement factor for cyanine chloride at 488 nm (in the absorption band) on a silver electrode and on a sol. Their estimate is a factor of about 50 for the colloid and 10" on the electrode. One should recall the difficulties inherent in such determinations (see Section II.I). 

These transformations, typically given by cyanine chloride, are reversed upon lowering the pH as shown in Scheme 3. At any given pH it appears that three or four structural entities may be present in varying proportions. 

C9H21CIN2O2, Bis(dimethyl)-pentamethine-cyanine chloride, 41B, 36 C9H22N2S2, Diethylammonium diethyldithiocarbamate, 44B, 28 C9H2 Ag,I13N2, N,N,N,N, N ,N -Hexamethylisopropylenediamine diiodide - silver iodide, 42B, 20... 

Between 1933 and 1935, a succession of liquid crystalline dye solutions were reported by Gaubert [16]. This was immediately followed by studies carried out independently by Jelley [17] and Schiebe et al. [ 18] on the aggregation of pseudo-isocyanine dyes in solution. Jelley describes the appearance of solutions of l l diethyl-p-cyanine chloride in terms of a fine thread-like... 

Crystal stmcture analyses of cyanine and related dyes are reviewed in Ref. 32. Most typical sensitizers are nearly planar, with angles of less than 15° between planes defined by heterocycHc rings. Distinct solvent of crystallization is present in most of the cationic dyes. X-ray crystal analyses also provide intermolecular data. Because of photographic use of cyanine and carbocyanine dyes, the cation-cation arrangements of most interest have been those for l,l -dieth5l-2,2 -quinocyanine chloride [2402-42-8] 5,5, 6,6 -tetrachloro-l,l, 3,3 -tetraethylbenzimidazolocarbocyanineiodide [3520-43-2] and 5,5 -dichloro-3,3, 9-triethylthiacarbocyanine bromide [18426-56-7] (32) (see Fig. 8). 

Tran [391,392] has reported ng detection of dyes on filter paper by SERS. Silver colloidal hydrosols stabilised by filter supports enhance the Raman scattering of adsorbed dyes. Typical detection limits are 500 pg (crystal violet), 7 ng (l,l,9-trimethyl-2,2 -cyanine perchlorate), 15 ng (3,3 -diethylthiacarbocyanine chloride) and 240 ng (methyl red) using a 3 mW He-Ne laser. 

The strategies used in the synthesis of polymethine dyes are illustrated for a series of indoline derivatives in Scheme 6.1. There is an even wider range of synthetic routes to polymethine dyes than is described here, but they are based for the most part on a similar set of principles. The starting material for the synthesis of this group of polymethine dyes is invariably 2-methylene-1,3,3-trimethylindolenine (121), known universally as Fischer s base. As illustrated in the scheme, compound 121 may be converted by formylation using phosphoryl chloride and dimethylformamide into compound 122, referred to as Fischer s aldehyde, which is also a useful starting material for this series of polymethine dyes. When compound 121 (2 mol) is heated with triethylorthoformate (1 mol) in the presence of a base such as pyridine, the symmetrical cyanine dye, C. I. Basic Red 12 109 is formed. The synthesis of some hemicyanines may be achieved by... 

Treatment of l-methyltetrazolo[5,l-tf]isoindolium perchlorate 49 with acyl chlorides and triethylamine in dioxane as solvent affords a mixture of the 5-acyl-l-methyltetrazolo[5,l-tf]isoindoles 50 and the monomethine cyanine dye 51 (Equation 2) <2004T195>. 

The cyanine dye, 3,3 -diethyl-9-methylthiacarbocyanine chloride, had a much greater effect than gelatin in decreasing the reaction rate of the silver chloride. The rate of reduction of silver chloride varied linearly with the amount of silver chloride surface not covered by the dye, and the rate attained at complete coverage was of the order of one-thousandth that for the undyed precipitate. The dye exerted scarcely any effect upon the reduction of silver ions from silver sulfite complex solution. 

The effect of the cyanine dye and of gelatin on the reaction rate shows that reduction of silver ions from solution is not the rate-controlling process. These influences of adsorbed components on the reaction rate speak against the concept that solution of the silver halide is the rate controlling process. Hence, the silver catalyzed reduction of silver chloride by hydroxylamine takes place substantially at the solid silver/ silver halide interface. 

Anthocyanins, in association with other compounds, such as flavones, are responsible for the colour of certain flowers. An anthocyanin found in rose petals is cyanin it can be isolated as its chloride. The corresponding anthocyanidin, cyan id in, exists as the pentahydroxy salt in acidic media, but as the pH increases it gives first a quinone and then an anion. Each of these forms has a different colour (see Scheme 5.1). 

The more basic benzimidazole-phosphamethin-cyanines can be easily protonated. In acetonitrile with 50% ethereal HBF4 the cyanine absorption bands at 440—421 nm and 347—335 nm(Table 1) of bis-[l,3-dimethyl-benzimidazole-2]-phosphacyanine disappear completely, A new sharp absorption at 300 nm (e = 30000) can be observed. Addition of tert-butanol restores 9C of the starting material, as can be seen by the spectrum. If the protonation is carried out in ethylene chloride with an excess of ethereal HBF4, the product can be isolated as a colorless, stable, but not analytically pure salt. Ethyldiisopropylamine or more ether will regenerate the cyanine. 

Mercuric chloride in methanol also reacts with compounds 8 (in dichloro-methane), forming colorless mercury complexes, which can in turn be reconverted to the cyanines 8. Such addition compounds are stable only as solids, decomposing rather quickly in solution. Mercuric acetate in methanol reacts rapidly with the formation of elemental mercury, where by the phosphamethin-cyanines are destroyed uniform products from this reaction have not as yet been isolated. 

One such reaction that has been studied is the electrocatalytic reduction of oxygen directly to water.25,27 The electrocatalysts for this process are often based on metal porphyrins and phthalo-cyanins. Thus a graphite electrode whose surface was modified by the irreversible adsorption of a cofacial dicobalt porphyrin dimer was able to reduce oxygen under conditions where the reduction did not occur on the bare electrode itself. Similarly, a catalytic chemically modified electrode for the oxidation of chloride to chlorine has been prepared28 where the active catalyst was reported to be a ruthenium dimer, [(bipy)2(OH)RulvORuvO(bipy)2]4+, which was reduced to the corresponding [Rum-RuIV] dimer during the reaction. 

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. 

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