Iron-complexed dyes

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. 

The stmcture of the blue material was not elucidated until 1934, when it was shown to be the iron complex of (67). The new material was christened phthalocyanine [574-93-6] reflecting both its origin from phthaUc anhydride and its beautihil blue color (like cyanine dyes). A year later the stmcture was confirmed by one of the first uses of x-ray crystallography. 

The only nitroso dyes important commercially are the iron complexes of sulfonated l-nitroso-2-naphthol, eg. Cl Acid Green 1 [57813-94-2] (78) (Cl 10020) these inexpensive colorants are used mainly for coloring paper. 

Naphthalene-3,7-disulfonic acid, 1,2-diamino-iron complexes filter dyes, 6,104 Naphthoic acid, hydroxy-metal complexes, 2, 480, 482... 

Table 12.30 Suitability of various sulphur dye types for application with anthra-quinonoid or iron-complex redox systems [214]...

Fearragillin, registered for use in aquaculture in Europe, 3 220t Feather meal, 10 856 Fe-base superalloys, 13 503 Fecal coliform analysis, of water, 26 45—46 Fe-complexed dyes, 9 446—447. See also Iron entries... 

The structures of metal-complex dyes, which must exhibit a high degree of stability during synthesis and application, is limited to certain elements in the first transition series, notably copper, chromium, iron, cobalt and nickel. The remaining members of the transition series form relatively unstable chelated complexes. The following description of the influence of electronic structure, however, is applicable to all members of the series. 

In 1929, Linsted obtained samples of this complex from ICI chemists (Scottish Dyes Ltd was now owned by ICI). ICI had developed two routes leading to the phthalocyanine iron complex. One method started from phthalic anhydride, iron, and ammonia, while the second pathway proceeded from phthalimide, iron sulfide, and ammonia. In 1933/34, elucidation of the phthalocyanine structure was credited to Linstead. The corresponding copper and nickel phthalocyanines had been prepared in the meantime. ICI introduced the first Copper Phthalocyanine Blue to the market as early as 1935, and the Ludwigshafen subsidiary of the IG Farben-industrie followed suit with a corresponding product. 

Sokolowska-Gajda, J., Freeman, H.S. and Reife, A. (1994) Synthetic dyes based on environmental considerations 1. Iron complexes for protein and polyamide fibers. Text. Res. f, 64 (7), 388-396. 

Iron, copper and nickel complexes of the products obtained by the nitrosation of arylazore-sorcinols have been claimed139 to dye leather in brown shades having excellent fastness to light. The structures of these products is open to debate since the position in which the resorcinol moiety is nitrosated (205 or 206) has not been established with any degree of certainty. Further, dyestuffs of this type, particularly those (207) derived from o-aminophenols, contain two metallizable systems and no information appears to be available regarding the stoichiometry and structure of their iron complexes. 

History. Braun and Tschemak [23] obtained phthalocyanine for the first time in 1907 as a byproduct of the preparation of o-cyanobenzamide from phthalimide and acetic anhydride. However, this discovery was of no special interest at the time. In 1927, de Diesbach and von der Weid prepared CuPc in 23 % yield by treating o-dibromobenzene with copper cyanide in pyridine [24], Instead of the colorless dinitriles, they obtained deep blue CuPc and observed the exceptional stability of their product to sulfuric acid, alkalis, and heat. The third observation of a phthalocyanine was made at Scottish Dyes, in 1929 [25], During the preparation of phthalimide from phthalic anhydride and ammonia in an enamel vessel, a greenish blue impurity appeared. Dunsworth and Drescher carried out a preliminary examination of the compound, which was analyzed as an iron complex. It was formed in a chipped region of the enamel with iron from the vessel. Further experiments yielded FePc, CuPc, and NiPc. It was soon realized that these products could be used as pigments or textile colorants. Linstead et al. at the University of London discovered the structure of phthalocyanines and developed improved synthetic methods for several metal phthalocyanines from 1929 to 1934 [1-11]. The important CuPc could not be protected by a patent, because it had been described earlier in the literature [23], Based on Linstead s work the structure of phthalocyanines was confirmed by several physicochemical measurements [26-32], Methods such as X-ray diffraction or electron microscopy verified the planarity of this macrocyclic system. Properties such as polymorphism, absorption spectra, magnetic and catalytic characteristics, oxidation and reduc-... 

Iron Complexes. Iron complexes of tridentate o,o -dihydroxyazo compounds are prepared under weakly acidic conditions at 40-80°C. Both Fe11 and Fe111 salts can serve as iron source. The Fem complexes that result in both cases do not have sufficient stability to dye textile substrates, but the dyeings on leather have good fastness properties [21],... 

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