Metallized dyes

In the presence of many metal ions, diorthohydroxyazo dyes exhibit two polarographic reduction waves, the first due to free dye and the second to metal-dye complex. Highly sensitive analytical methods based on this principle have been developed for example, Ni or Fe may be determined in the presence of an excess of aluminum thank to thiazolylazo derivatives (563). 

Metallic dyes Metallic fibers Metallic glass Metallic pinwheels Metallic soaps... 

Hair coloring preparations have been in use since the ancient Egyptians, and recorded recipes exist in many cultures. These followed the traditional apphcation of plant extracts or metallic dyes, both of which still are used. In the latter part of the nineteenth century, synthetic organic compounds were discovered which eventually led to modem hair coloring. 

Metallic Dyes. MetaUic dyes are among the older hair color materials known. Commercial products are based on a 1% solution of lead acetate in an aqueous, slightly acidic, alcohoHc medium. Precipitated sulfur appears to be essential. The convenience aspect is stressed by the leave-in appHcation method. Actually, the color development is so slow, taking about a week to ten days, that there is no alternative to this technique. Daily appHcation is needed at first. 

Although lead acetate [301-04-2] is the only metallic dye used ia the early 1990s, salts or silver, copper, nickel, cobalt, bismuth, and iron have been utilized ia the past. A patent (39) refers to the use of bismuth citrate ia a solution made alkaline with triisopropan ol amine. 

In contrast to metal complexes of OjoTydroxyazo types, these terminally metallized dyes derived from the o-hydroxy carboxyl stmctures undergo httie color change on metallization and exhibit Httie improvement ia lightfastness (49). 

Polacolor. The first instant color film, Polacolot, was introduced by Polaroid Corporation in 1963. Polacolot was replaced in 1975 by Polacolot 2, a film with improved light stabiUty, which utilizes the metallized dye developers shown in Eigute 4. An extended range version, Polacolot ER, introduced in 1980, utilizes the cyan and yeUow metallized dye developers together with a magenta dye developer that incorporates a xanthene dye having reduced blue absorption (see Eig. 5). 

Metal Introduced Into the Dyestuff Molecule in Manufacture. These dyes fall into two categories according to the ratio of metal cation to dye molecule anion 1 1 metal dye complexes comprise one metal cation and one chromophoric ligand and 1 2 metal dye complexes comprise one metal cation and two chromophoric ligands. 

An example of a 1 1 metal dye complex is shown in Figure 5a. The net charge on the molecule is derived from the plus three charge on chromium,... 

With 1 2 metal—dye complexes the coordination number of the metal is fuUy satisfied so no reaction can take place with the amino groups in the wool. A representative stmcture is shown in Figure 5b. 

Metal Complex Dyes. The 1 1 metal—dye complexes caimot be used on nylon because the low pH values needed cause fiber degradation. 

The 1 2 metal—dye complexes are of commercial interest because of their excellent lightfastness in pale shades. These macromolecules are difficult to apply level and are sensitive to both chemical and physical variations. In their appHcation they are treated as the Group 3 acid dyes. 

Salz-farbe,/. metallic dye, dye salt, -fehler, m. salt error, -fleisch, n. salt meat, -fiuss, m.. saline flux salt rheum, eczema, salz-fdrmig, a. saliniform. -frei, a. free from salt, salt-free. 

In general, coordination complexes and metallized dyes exhibit higher photochemical stability than purely organic molecules so it is clear that coordination chemistry has a major role to play in the future development of ODS media. 

It has been estimated that 200 to 300 agents have been identified as inducers of occupational asthma [4], The LMW agents can be broadly classified by chemical class such as isocyanates, anhydrides, metals, dyes, amines, drugs, acrylates and other compounds. The HM W agents can be broadly classified as animal protein, plant protein and microbial byproducts. Table 33.1 shows apartial listing of LMW and HMW sensitizers along with the workplace environments where these agents can be encountered. 

Metallized azo dyes, 9 250-251 Metallized dye developers, 19 286 Metallized dyes, stability of, 19 296 Metallizing, ABS, 1 428. See also Metalbzation... 

In a bidentate ligand system, three molecules of a dye containing either a terminal salicylic acid unit (as in 5.2) or an o-nitrosonaphthol residue are able to chelate simultaneously with a trivalent metal ion of CN6, such as chromium (III) or iron(III), to form a 1 3 metal-dye complex (as in 5.8). Historically, the most important bidentate ligand system was alizarin (5.1). It has been suggested that both hydroxy groups and the keto group in the peri position are all involved with the metal atom in the chelation mechanism. 

Salicylic acid has been found useful as a terminal coupling component in direct or mordant dyes to provide a bidentate site for metallisation. The free acid is also capable of complexing and ammonium chromisalicylate (5.12) is used as an intermediate in the synthesis of metal-dye complexes. Cl Mordant Orange 1 (5.3) and Yellow 5 (5.13) are examples of dyes... 

The unfilled sites in 1 1 metal-dye complexes of chromium(III) or cobalt(III) ions can be... 

The replacement reactions may be represented generally by a two-stage process. Introduction of the first tridentate monoazo dye ligand D2 is the rate-determining step (Scheme 5.7). Where a typical o,o -dihydroxyazo dye ligand is used in excess with a hydrated chromium (III) salt under alkaline conditions (pH >9) favouring 1 2 metal-dye complex formation, none of the 1 1 complex remains. This indicates that the presence of one... 

Various chromium-complex dyes were prepared recently by reacting ammonium chromium sulphate with a series of chelatable o,o -dihydroxyazopyridone structures (Scheme 5.9). Elemental analyses corresponded to a 1 2 metal-dye ligand ratio (5.35). The... 

An important subclass of black reactive dyes for the dyeing of cellulosic fibres consists of symmetrical 1 2 metal-dye complexes in which the metal content is a deliberate mixture of chromium (III) and cobalt (III) ions, usually rich in the chromium component. The two most important structural types are the nitrophenylazo H acid complex 5.40 and the nitronaphthylazo J acid complex 5.41. In both cases, each reactive system Z is linked to the NH site in each coupling component. 

Symmetrical premetallised 1 2 metal-dye complexes of unsulphonated monoazo structures with aluminium (5.57) or trivalent iron (5.58) have been patented recently for use as solvent dyes [36]. They contain a polar methoxypropylaminosulphone grouping in each diazo component and are marketed as alkylamine salts. It remains to be seen, however, whether a full colour gamut of bright aluminium and iron complex dyes can be discovered with light fastness performance equivalent to that of currently available chromium and cobalt complex dyes. 

Buryak, A. Severin, K. Easy to optimize Dynamic combinatorial libraries of metal-dye complexes as flexible sensors for tripeptides. J. Comb. Chem. 2006, 8, 540-543. 

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