Metallic complexes of azo dyes

Virtually every conceivable chromophore has been used in the synthesis of reactive dyes, including monoazo and disazo species, metal complexes of azo dyes, formazan dyes, anthraquinones, triphenodioxazines, and phthalocyanines. The product lines offered by the major dye producers in most cases feature comparable chromophores, differing primarily in the nature of the reactive systems and the particular substitution patterns adopted. 

METAL COMPLEXES OF AZO DYES Metal complexes of certain 0,0 -dihydroxyazo, 0-carboxy-0 -hydroxyazo, o -amino-o hydroxyazo, arylazosalicyclic acid, and formazan compounds are used as dyes for wool, nylon, and cotton with generally much improved washfastness and lightfastness properties when compared to their respective unmetallized precursors. Dyes that are chelated with the metal on the substrate during the dyeing process are termed metallizable or mordant dyes. Conversely, those dyes that have been metallized by the dye manufacturer prior to use by the dyer, are classified as premetallized dyes. The two important types of premetallized dyes are the 1 1 and 2 1 complexes, eg, complexes with 1 1 and 2 1 ligand-to-metal ratios, respectively. 

Section 2 of this review covers the literature dealing with NMR spectra of azo dyes measured in solution since the publication of last review in 1993 and focuses on azo compounds. Hydrazo compounds have been included either when prepared by diazonium salt coupling reactions or when they are important for azo-hydrazone tautomerism description. The C and N CP/MAS NMR spectra are discussed in Section 3. Azo-hydrazone tautomerism, a property that is indivisibly linked to azo dyes, is the topic of Section 4. NMR spectra of metal complexes of azo dyes are reviewed in Section 5. 

Triphenylformazan behaves as a bidentate ligand forming 2 1 complexes (217) with divalent copper, nickel, and cobalt.377 Formazan metal complexes can be compared to complexes of azo dyes or beta diketones due to structural similarity.301,302 In general, formazan metal complexes have low stability toward acids. However, when electron-donating substituents are added to the aromatic ring, a considerable enhancement in stability is observed. Cationic complexes of type 218 are also known. The complexation of formazan with metal cation can be accompanied by oxidation to the tetrazolium salt and the formation of a complex... 

Metal complexes of azo and azomethine dyes are an important class of industrially relevant pigments. Such pigments possess more advantageous properties compared to their parent chromophore including bathochromic shift of absorption, better weather- and lightfastness and enhanced solvent resistance [90]. 

Used as a soln. in dichloroethane for extraction-separation of metal complexes with azo dyes. Cryst. Mp 102-103°. 

The second type is comprised of 2 1 metal complexes of OjO -dihydroxy azo dyes which generally do not contain sulfo or other strongly hydrated groups as found ia the premetallized 2 1 complexes for wool. Thus their solubiUty ia esters, ketones, and alcohols is relatively iacreased. Cl Solvent Violet 1... 

Good non-colored negative charging CCAs have been obtained by making non-colored analogues of the 2 1 chromium complex azo dyes. This is achieved by making the metal complex of an aromatic ortho-hydroxy carboxylic acid. Typical examples are the chromium, aluminum, and zinc complexes of di-tert-butyl salicylic acid, e.g., BONTRON E-8136 41 (53) and BON-acid36,41,42 e.g., BONTRON E-82 (54). 

Metal complexes, 7 573 luminescent, 26 802 of azo dyes, 9 394-401 Metal Complex Yellow, pigment for plastics, 7 366t... 

The interaction of metallochromic indicators (Section 10.6.4) with metals has received a lot of attention since the resulting complexes are often solvent extractable. C. Woodward and H. Freiser73 have examined complexes of metals with sulfonated azo dyes with a view to their extraction by Aliquat-336. Vanadium in sea water can be determined at the 2 p.p.b. level by complexation with PAR (4-(2-pyridylazo)resorcinol) in the presence of CDTA and extracting the anion so formed into Zephiramine (tetradecyldimethylbenzylammonium chloride).74 The field has been reviewed up to 1971 by Ueno.2... 

A recurring theme throughout all the reported work on isomerism in metal complexes of tridentate azo compounds is the facility with which individual isomers revert to equilibrium mixtures in solution at elevated temperatures. Since these are the very conditions under which most metal complex dyes are applied, little technical application can be seen for the phenomenon of isomerism on dyes of this type. Nonetheless, the subject is of considerable theoretical interest and merits inclusion in this chapter on those grounds alone. 

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). 

MULTINUCLEAR NMR OF AZO DYES AND THEIR METAL COMPLEXES 17 Omura et al.79 reported <5(1SN) chemical shifts in compounds 19 (Table 8). 

---