Indanthrones

In some cases, a single chemical substance can serve both as a dye and as a pigment. For example, indanthrone [81-77-6] (Pigment Blue 60) functions as a blue pigment or as a dye. As a pigment, indanthrone is a particulate, insoluble soHd dispersed directly into a vehicle, whereas as a dye it is reduced to a base-soluble hydtoquinone derivative and then reoxidized onto a soHd substrate. 

Pigment Blue 60 [81-77-6] 69800 indanthrone intermolecular condensation of 2-amino-anthtaquinone in presence of a strong inorganic base and oxidi2ing agent... 

Practical methods for synthesis and elucidation of the optimum physical forms were developed at Du Pont (13). The violets fill the void in the color gamut when the inorganics are inadequate. The quinacridones may be used in most resins except polymers such as nylon-6,6, polystyrene, and ABS. They are stable up to 275°C and show excellent weatherabiUty. One use is to shade phthalocyanines to match Indanthrone Blue. In carpeting, the quinacridones are recommended for polypropylene, acrylonitrile, polyester, and nylon-6 filaments. Predispersions in plastici2ers ate used in thermoset polyesters, urethanes, and epoxy resins (14). 

Although the colors of the polycycHc aromatic carbonyl dyes cover the entire shade gamut, only the blue dyes and the tertiary shade dyes, namely, browns, greens, and blacks, are important commercially. Typical dyes are the blue indanthrone [81-77-6] (40), the brown Cl Vat Brown 3 [131-92-0] (Cl 69012), (41), the black Cl Vat Black 27 [2379-81-9] (42), and the green Cl Vat Green 1 [128-58-5] (Cl 59825) (43), probably the most famous of all the polycycHc aromatic carbonyl dyes. 

In 1901, mercury cataly2ed a-sulfonation of anthraquinone was discovered, and this led to the development of the chemistry of a-substituted anthraquinone derivatives (a-amino, a-chloro, a-hydroxy, and a,a -dihydroxyanthraquinones). In the same year R. Bohn discovered indanthrone. Afterward flavanthrone, pyranthrone, and ben2anthrone, etc, were synthesi2ed, and anthraquinone vat dyes such as ben2oylaniinoanthraquinone, anthrimides, and anthrimidocarba2oles were also invented. These anthraquinone derivatives were widely used to dye cotton with excellent fastness, and formed the basis of the anthraquinone vat dye industry. 

Some anthraquinone dyes are employed as organic pigments (see Pigments, organic). Examples appear in Figure 1. Indanthrone blue (6) is an important automotive paint pigment as is Cl Pigment Red 177 (7), a bisanthraquinonyl. 

Fig. 1. Anthraquinone dyes used as organic pigments (4) = dibromoan than throne [4378-61-4] (Cl Pigment Red 168 Cl Vat Orange 3 Cl 5930G) (5) = an anthrapyrimidine [4216-01 -7] (Cl Pigment YeUow 108 Cl Vat YeUow 20 Cl 68420)-, (6) = indanthrone blue [81-77-6] (Cl Pigment Blue 60 Cl Vat Blue 4 ...

The anthraquiaone vat dyes can be classified into several groups on the basis of their chemical stmctures (/) benzanthrone dyes, (2) indanthrones, (3) anthrimides, (4) anthrimidocarbazoles, (5) acylaminoanthraquinones, (6) anthraquinoneazoles, (7) anthraquiaone acridones, (8) anthrapyrimidines, and 9) highly condensed ring systems. Most currendy (1993) available dyes have been known for many decades, and very few new dyes have been commercialized since the 1970s. Recendy, research and development efforts have focused on improved manufacturing of traditional vat dyes. 

Indanthrones. Indanthrone blue (Cl Vat Blue 4) [81-77-6] (6) (Cl 69800) is the first invented anthraquinone vat dye, and has been extensively used as the most important vat dye for many decades because of its bright color as well as excellent affinity and fastness. These advantages are considered to be due to the stable stmcture attained by the intramolecular hydrogen bonding (145). 

Chlorination of indanthrone in sulfuric acid by passing through chlorine gas with addition of a small amount of manganese dioxide affords Cl Vat Blue 14 as well as Cl Vat Blue 6. 

The relative importance of structures 130 and 131 have long been discussed for the dye indanthrone. Initially, the infrared spectrum was considered to favor 131 ° because a vN—H band could not be found. However, this interpretation has been questioned, and recently the predominance of structure 130 was established by Weinstein and MerritP on the basis of the following evidence (a) a... 

V NH band is present in the infrared spectra of both indanthrone and mono-A -methylindanthrone, (h) the infrared spectra of indanthrone and its mono- and di-A -methyl derivatives showed vC—O bands of approximately equal intensity, and (c) the ultraviolet and visible spectra of indanthrone and its A -methyl derivatives are similar. 

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... 

The syntheses of three polycyclic anthraquinones, indanthrone (53), pyranthrone (55a) and flavanthrone (55b), are illustrated in Scheme 4.7. In spite of the structural complexity of the products, the syntheses of these types of compound are often quite straightforward, involving, for... 

Scheme 4.7 Syntheses of the polycyclic anthraquinones indanthrone (53), pyranthrone (55a) and flavanthrone f55b)...

A number of vat dyes developed originally for textile applications are suitable, after conversion into an appropriate pigmentary physical form, for use in many paint and plastics applications. Examples of these so-called vat pigments include the anthraquinones, Indanthrone Blue (215, C. I. Pigment Blue 60) and Flavanthrone Yellow (216, C. I. Pigment... 

Hydroxyacetone (12.48), mentioned in section 12.8.1 in connection with sulphur dyes, is sulphur-free and biodegradable. This compound was originally proposed for use with vat dyes and continues to generate some interest. This agent can be used for the pad-steam application of vat dyes in the presence of high concentrations of sodium hydroxide (about 3.5-4.5 g/1). Hydroxyacetone does not cause over-reduction of indanthrone vat dyes but does give different shades with carbazole dyes, compared with sodium dithionite [218]. 

Blue - cobalt blue, indanthrone, a-copper phthalocyanine... 

Indanthrone has low fastness to bleaching because the corresponding yellowish green azine (6.66) is formed. Its importance at the time of its discovery lay in the dearth of fast dyes for cotton. Indanthrone is also used as a pigment (Cl Pigment Blue 60). 

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