Azines and Dyes

Azines and Dyes.—In their wider investigation of two-stage redox systems, Hiinig and Sauer have studied the reversible oxidation of thiazol-2-one azines (121) to (122) and (123). The required model-compounds (121) are 

A series of / -dialkylaminostyryl dyes (124), their aza- (125), and diaza-analogues (126), all derived from 4,5-diarylthiazoles, have been prepared by existing methods and their light absorption examined. The replacement 

Thiazolocyanines of type (127) and (128), derived from 3,5-diaryl-thiazolium salts, have been described. Further examples are given in the section dealing with the alkylation of thiazoles (p. 597). 

Metal Complexes.—In an extensive study of the complexing power of thiazoles, numerous zinc(n), cobalt(n), copper(ii), nickel(ii), andplatinum(n) complexes of the parent compound, and of 4-alkyl- or 2,4-dialkyl-thiazoles, usually of the general type MX2L2, have been prepared. A consideration of their spectral and magnetic properties reveals that the zinc and cobalt complexes are tetrahedral, the 4-methyl copper and nickel complexes are octahedral, and the dialkyl complexes of copper and nickel and the platinum complexes are square planar. The four-co-ordinate dialkyl complexes follow the crystal field stabilization energy predictions as to the relative tendency to form tetrahedral or square-planar forms, i.e. Zn Co Cu Ni. The complexes are invariably metal-nitrogen, and not metal-sulphur, co-ordinated.  

2-Methylthiazol-4-yl phenyl ketoxime forms a chloroform-soluble green complex with copper(n) salts. Spectrophotometric measurements show that each metal ion binds two molecules of ligand. 3,4-Dialkyl-thiazolium halides and thiamine yield solid adducts with zinc(n) and cobalt(u) halides. According to their spectra and magnetic susceptibilities they appear to be complex salts without metal-sulphur or metal-nitrogen interaction.  

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