Bromine-containing dyes

Odier bromine-containing dye intemiediates include 6-bromo-2,4-dinitroaniline [1817-73-8] C H BrN O, and 5,7-dibromoisatin [6374-91-0] CgH2Bi2N02. Bromodinitroaniline is used in making a2o dyes and dibromoisatin is used in making Alizarin Indigos B, 3R, and G. 

The bromine-containing dyes were prepared by Lewis and Uteeht which are described here A. 3-Bromo-4 (hexylamino)-N-hexyl-l, 8-naphthalimide... 

A pyridinyl-functionalized ionic liquid, iV-butyl-]V -(4-pyridyIhept-yl)imidazolium bromide, cf. Figure 2.38, has been S5mthesized and applied as an additive for dye-sensitized solar cells (129). In comparison to a volatile organic additive, 4-tert-butyl pyridine, the bromine-containing compound can be used at a very low concentration for high overall power conversion efficiency cells, which shows an overall power conversion efficiency of 5.67% under the simulated air... 

In addition to the processes that can compete with fluorescence within the molecule itself, external actions can rob the molecule of excitation energy. Such an action or process is referred to as quenching. Quenching of fluorescence can occur because the dye system is too warm, which is a very common phenomenon. Solvents, particularly those that contain heavy atoms such as bromine or groups that ate detrimental to fluorescence in a dye molecule, eg, the nitro group, ate often capable of quenching fluorescence as ate nonfluorescent dye molecules. 

In addition to benzenoid diazo components, diazotised heterocyclic amines in which the amino group is attached to a nitrogen- or sulphur-containing ring figure prominently in the preparation of disperse dyes [87,88], since these can produce marked bathochromic shifts. The most commonly used of these are the 6-substituted 2-aminobenzothiazoles, prepared by the reaction of a suitable arylamine with bromine and potassium thiocyanate (Scheme 4.31). Intermediates of this type, such as the 6-nitro derivative (4.79), are the source of red dyes, as in Cl Disperse Red 145 (4.80). It has been found that dichloroacetic acid is an effective solvent for the diazotisation of 2-amino-6-nitrobenzothiazole [89]. Subsequent coupling reactions can be carried out in the same solvent system. Monoazo disperse dyes have also been synthesised from other isomeric nitro derivatives of 2-aminobenzothiazole [90]. Various dichloronitro derivatives of this amine can be used to generate reddish blue dyes for polyester [91]. 

These classes of chemicals contain not only some of the oldest dyes, dating back to the 19th centnry, bnt also some of the most important flnorescent chromophores. The earliest of these discoveries was flnorescein (3.21), which was later brominated to give the polybromo derivative eosin (3.22) (Fignre 3.10). They are of little importance in textile coloration processes bnt are nsed in some fluorescent pigments and extensively in analysis and biological methods and also in tracing the course of water in drains and other water outlets. 

E. Marchand10 has reported the presence of. traces of bromine in rain and snow. The ashes of many sea weeds and sea animals contain bromine—thus, dried Fucus vesiculosus contains 0 682 per cent, of bromine.11 Bromine has been reported in human urine, salt herrings, sponges, and cod liver oil but not in bone ash. Indeed, all products directly or indirectly derived from sea-salt or from Stassfurt deposits— in the present or in the pash—contain bromine. It is also said to be an essential constituent of the dye Tyrian purple which was once largely obtained from a species of marine gastropod or mollusc. 

Non-tellurium-containing type-123 trimethine dyes have been found recently to be susceptible to a reaction with chlorine and bromine (93MI1 94MI1). In this case, however, the reaction is rather slow and occurs at the trimethine bridges. For the formation of dihalogenides 124, halogens must be present in at least 2.5-fold excess to the initial trimethine cyanine 122. 

A fairly new major use for bromine is in clear completion fluids used in crude oil production. These are concentrated solutions of CaBr2 or CaBr2-ZnBr2, which have a high density. Several hundred pharmaceuticals contain bromine atoms. Other moderate-sized markets for bromine compounds are in photography, water treatment chemicals, extinguisher fluids, and dyes. 

The elemental composition is useful for characterisation of inorganic pigments and organic dyes. However, a database is needed for their identification. In all ballpoint pen inks, sulfur, copper, silicon and phosphorus are present in the elemental composition. Some samples also contain zinc, chlorine, bromine and calcium. In black inks, chromium and lead are additionally found. Samples differ with respect to the elemental composition quantitatively rather than the qualitatively. A greater variability in elemental content is observed for gel inks. 

The same pigment containing bromine atoms in the molecule was also isolated from the secretion of the marine sea shell Purpura aperta used for dyeing by the native peoples of Mexico and Costa Rica, and also from European P. lapillus [7]. 

Halogen-containing compounds are not only produced by man, but also by Nature [1740-1742], A brominated indole derivative - Tyrian purple dye - was isolated from the mollusc Murex brandaris by the Phoenicians. Since that time, more than 1,000 halogenated natural products of various structural types have been isolated from sources such as bacteria, fungi, algae, higher plants, marine molluscs, insects, and mammals [1743], Whereas fluorinated and iodinated species are rather rare, chloro and bromo derivatives are found more often. The former are predominantly... 

Tyrian purple 6,6 -dibromoindigotin, a red-violet pigment containing two brominated and oxidized indole ring systems. Tp. is present in marine moUusks of the genera Murex and Nucella, and a few related whelks. The isolation and structural elucidation of Tp. from the hypobranchial body of the purple snail Murex brandaris were performed by Friedlander between 1909 and 1911. In antiquity and later in the Middle Ages, Tp. was one of the most expensive dyes. 

Intersystem crossing will obviously be accelerated by heavy-atom sub-stitutients, and no efficient laser dye contains them. The four bromine atoms in eosin (Fig. 9.7) increase its - ISC yield to 76%, as compared to the 3% value observed in fluorescein. Solvents containing heavy atoms (e.g., CBr4) also contribute to buildup in laser dyes, and are avoided. 

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