Anthraquinone Chromophore

Once the second most important class of dyes, it also includes some of the oldest dyes they have been found in the wrappings of mummies dating back over 4000 years. In contrast to the azo dyes, which have no natural counterparts, all the important natural red dyes were anthraquinones [1]. However, the importance of anthraquinone dyes has declined due to their low cost-effectiveness. 

Anthraquinone dyes are based on 9,10-anthraquinone (1), which is essentially colorless. To produce commercially useful dyes, strongly electron donating groups such as amino or hydroxyl are introduced into one or more of the four a positions 

The strength of electron-donor groups increases in the order OH NH 2 NHR HNAr. Tetrasubstituted anthraquinones (1,4,5,8-) are more bathochromic than di- (1,4-) or trisubstituted (1,2,4-) anthraquinones. Thus, by an appropriate selection of donor groups and substitution patterns, a wide variety of colors can be achieved. 

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The anthracyclines are aminoglycosidic derivatives of tetracyclic compounds that contain an anthraquinone chromophore. Originally, dauno-mycin and adriamycin, its hydroxy analogue, were isolated from cultures of Streptomyces peucetiusd The main target of these drugs appears to be DNA, most likely by formation of an intercalation complex. The drugs also affect topoisomerase II, an enzyme which interacts with the DNA that has been modified by intercalation. ... 

The hydroxylated anthraquinone chromophore of the anthracyclines would seem an ideal candidate for synthesis through two Friedel-Crafts acylations, either in a concurrent or a stepwise manner with formation of ring C. However, the fact that the first acylation deactivates the future ring B toward further electrophilic substitution necessitates vigorous reaction conditions, and this... 

Addition of sodium dithionite to formaldehyde yields the sodium salt of hydroxymethanesulfinic acid [79-25-4] H0CH2S02Na, which retains the useful reducing character of the sodium dithionite although somewhat attenuated in reactivity. The most important organic chemistry of sodium dithionite involves its use in reducing dyes, eg, anthraquinone vat dyes, sulfur dyes, and indigo, to their soluble leuco forms (see Dyes, anthraquinone). Dithionite can reduce various chromophores that are not reduced by sulfite. Dithionite can be used for the reduction of aldehydes and ketones to alcohols (348). Quantitative studies have been made of the reduction potential of dithionite as a function of pH and the concentration of other salts (349,350). 

Pyrazolone dyes are particularly versatile yellow chromophores the yellow dye developer used in Polacolor, the first instant color film, was based on a pyrazolone dye. The stmctures of the three Polacolor dyes are shown in Figure 3. The study of azo dyes derived from 4-substituted 1-naphthols led to the chromophore used in the Polacolor magenta dye developer. The Polacolor cyan dye developer contained a 1,4,5,8-tetra-substituted anthraquinone as chromophore (20). 

Production of anthraquinone reactive dyes based on derivatives of bromamine acid (8) was first commercialized in 1956. Some improvements have been made and now they ate predominandy used among the reactive blue dyes. Cl Reactive Blue 19 [2580-78-1] (9) (Cl 61200) (developed by Hoechst in 1957) has the greatest share among them including dye chromophores other than anthraquinones. 

Several basic chromophore stmctures have been proposed for this purpose. Anthraquinone dyes appear to be predominant since they have a wider color range, excellent photostabiHty, good solubiHty in Hquid crystal media, and very high order parameters. Typical basic stmctures of the three primary colors are illustrated in Figure 11. Some examples are given in Table 10. The appropriate combination of three primary colors gives a black display. 

Water-soluble polymeric dyes have been prepared from water-insoluble chromophores, viz., anthraquinone derivatives. Unreacted chromophore and its simple derivatives, which are all water-insoluble, remain in solution due to solubilization by the polymeric dye. A method has been developed to separate and quantitate the polymeric dye and these hydrophobic impurities using Sephadex column packing. The solvent developed has the property of debinding the impiirities from the polymer, and further allows a separation of the imp irities into discrete species. This latter separation is based on the functional groups on the impurity molecules, having a different interaction with the Sephadex surface in the presence of this solvent. The polymer elutes at the void volume... 

Anthraquinone leuco dyes are widely known as vat dyes.10 Vat dyes possess extensively conjugated aromatic systems containing two or more carbonyl groups, e.g., anthraquinone, indigoid chromophores. The colored form of vat dyes are insoluble in water. The dyes are applied by a process whereby the dye is converted to the reduced form (leuco dye) which is soluble in water and can penetrate into a cellulosic fiber. On exposure to the atmosphere the leuco form is oxidized to the original quinoid form which then precipitates as an aggregate. Vat dyes generally have excellent chemical and photochemical stability. 

Indigo is the most important vat dye, dating back to ancient times and produced on an industrial scale since 1880. To replace the indigo dyes, the indanthrone (21) class of dyes was developed. Indanthrone has superior characteristics as a vat dye and became a key material for further development of anthraquinoid vat dyes. There exist a variety of anthraquinone vat dyes differing in the chromophoric system. The color-structure relationship of vat dyes have been rationalized by the Pariser-Parr-Pople molecular orbital (PPP MO) method. Some examples of commercialized anthraquinoid vat dyes are shown in Scheme 6.14... 

These chromophores have declined significantly in importance as textile dyes bnt have remained of interest becanse of their fluorescent behaviour, as discussed in Chapter 3, section 3.5.1.5. One exception is the triphenodioxazine ring system, which is used to produce valuable blue dyes in the Direct (2.19) and Reactive dye classes (2.20) as well as pigments (see section 2.4.1.7). The dyes from this chromogen have a very high molar absorption coefficient (ca. 80 000) versus typical anthraquinone dyes (ca. 15 000) and have therefore replaced some of the dyes from this latter chromogen in the reactive dyeing of cotton. ... 

The anthraquinone mitoxantrone (63) is a clinically useful antineoplastic agent. This compound contains a planar chromophore that could potentially insert or intercalate... 

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