Metal-Complex Dyes Sulfonic Acid Groups

Chromium Complexes Containing Sulfonic Acid Groups. The production of premetallized complex dyes began in 1912, when R. Bohn of BASF synthesized 1 1 chromium complexes and BA SF and CIBA introduced ranges of sulfonic acid containing 1 1 chromium complex azo dyes. No metal other than chromium is suitable for this class of dyes. 

Dyes and Pigments. Several thousand metric tons of metallated or metal coordinated phthalocyanine dyes (10) are sold annually in the United States. The partially oxidized metallated phthalocyanine dyes are good conductors and are called molecular metals (see Semiconductors Phthalocyanine compounds Colorants forplastics). Azo dyes (qv) are also often metallated. The basic unit for a 2,2 -azobisphenol dye is shown as stmcture (11). Sulfonic acid groups are used to provide solubiHty, and a wide variety of other substituents influence color and stabiHty. Such complexes have also found appHcations as analytical indicators, pigments (qv), and paint additives. 

Another important class of pigment are the so-called toner pigments. These are water-soluble dyes containing sulfonic acid groups which are insolubilized by forming a salt with a divalent cation such as calcium and barium5 (Scheme 2). Until recently the toner pigments were perceived merely as insoluble salts but X-ray studies have shown them to exist as supramolecular metal complexes (see Section 9.12.4.2). 

The most recent development in this area is the 1 2 metal-complex dyes with two sulfonic acid groups. Contrary to the opinion frequently expressed in the literature that such dyes would exhibit inadequate levelness when applied in a weakly acid bath and inadequate stability to acid in a strongly acidic dyebath,... 

Chromium Complexes with One Sulfonic Acid Group. By definition, l 2-metal complexes with one sulfonic acid group must be unsymmetrical, because only one of the two azo dye ligands bears a sulfonic acid group. In 1962 the first metal-... 

Acid dyes, i.e., azo or anthraquinone dyes containing sulfonic acid groups, were occasionally used for dyeing cotton however, they are no longer important. They do not have sufficient substantivity for cellulose. Only those dyes are usable that can form a metal complex on the fiber when applied together with a metal salt. Excess heavy metal contaminates the wastewater. 

Certain dyes when appHed by the afterchrome method are oxidized prior to metal complex formation. Examples iaclude. Chromotrope EB [3567-69-9] (52) (Cl Acid Red 14 Cl 14720) (naphthionic acid — l-naphthol-4-sulfonic acid) ia which a hydroxyl group is iatroduced by oxidation at the... 

Acid Dyes. These water-soluble anionic dyes ate appHed to nylon, wool, sUk, and modified acryHcs. They ate also used to some extent for paper, leather, food, and cosmetics. The original members of this class aU had one or mote sulfonic or catboxyHc acid groups in thein molecules. This characteristic probably gave the class its name. Chemically, the acid dyes consist of azo (including preformed metal complexes), anthraquiaone, and ttiaryHnethane compounds with a few azHie, xanthene, ketone imine, nitro, nitroso, and quHiophthalone compounds. 

First, 1 2 metal complexes of (mainly mono-) azo dyes, without sulfonic or carboxylic acid groups, and trivalent metals (see Section 3.11). The metals are preferably chromium and cobalt nickel, manganese, iron, or aluminum are of lesser importance. Diazo components are mainly chloro- and nitroaminophenols or amino-phenol sulfonamides coupling components are (3-naphthol, resorcinol, and 1-phe-nyl-3-methyl-5-pyrazolone. Formation of a complex from an azo dye and a metal salt generally takes place in the presence of organic solvents, such as alcohols, pyridine, or formamide. An example is C.I. Solvent Red 8, 12715 [33270-70-1] (1). 

Second, 1 1 metal-complex azo dyes that contain sulfonic acid or carboxylic acid groups and are present in the form of internal salts. Here, azamethine-metal complexes are also of importance. An examples is C.I. Solvent Yellow 32, 48045 [61931-84-8] (2). 

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