Formazans tetradentate

Formazan, l-(2-hydroxy-5-suIfophenyl)-3-phenyl-5-(2-carboxyphenyl)-zinc detection, 6, 83 Formazans cobalt complexes dyes, 6, 81 metal complexes bidentate, 6, 78 color photography, 6,111 dyes, 6, 77 tetradentate, 6, 81 tridentate, 6, 79... 

A variety of complexes, e.g., 224 and 225, can be formed from the tetradentate formazans.384,385,388 396 Tetradentate formazans containing heterocycles, e.g., 226 and 227, also form metal complexes.385... 

There are bi-, tri-, and tetradentate formazan dyes7 but only the tetradentate copper complex formazan dyes have found use as commercial products. The dye Cl Reactive Blue 160, of generic structure (41), is a representative example. Because of the intensity of their colors, the metal complex formazan dyes have also found application in analysis. Thus, the dye (42) detects zinc at a concentration of 1 part in 50 million.31... 

Comparison117129 of the behaviour of bidentate, tridentate and tetradentate formazans with copper(II) salts has effectively demonstrated that two competing reactions occur copper complex formation (equation 16) and oxidation of the formazan to tetrazolium salt (equation 17). 

The preparation of chromium(III) and cobalt(III) complexes of tetradentate formazans in which the coordination sphere of the metal is completed by a variety of neutral ligands has been reported116 and these (185) were claimed to be very stable towards acids. By analogy with copper complexes, however, some doubt must exist regarding the structures assigned to those complexes derived from l,5-bis(2-carboxyphenyl)formazans. Various dyestuff and pigment applications have... 

Metallization. Bident ate formazans that are insoluble in water can be warmed with cobalt, nickel, and copper salts (preferably acetates) to form metal chelates in solvents such as methanol, ethanol, acetone, and dimethylformamide. Metal complexes of tri- and tetradentate formazans are much more stable. Metallization with divalent salts occurs rapidly at room temperature. On reaction with diazo-tized 2-aminophenols or 2-aminonaphthols, coupling and metallization with divalent metal salts can take place concurrently under the same conditions. When coupling is complete, the dye is usually fully metallized. 

Metal Containing Tetradentate Formazans. Formazans with two complex-forming groups in the 2- and 2 -positions of the N1- and N5-aryl substituents are potential quadridentate ligands. They form 1 1 coordination complexes with four- and six-coordinate metals ... 

Formazan dyes bear a formal resemblance to azo dyes, since they contain an azo group, but have sufficient structural dissimilarities to be considered as a separate class. The most important formazan dyes are the metal complexes, particularly copper complexes, of tetradentate formazans (see Section 2.10.3). They are used as reactive dyes for cotton (12) is a representative example. 

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