Azo Metal-Complex Dyes

A study similar to that of Hersey and Robinson has been reported by Seiyama and coworkers.From a stopped-flow, kinetic study of the interaction of various azo dyes and some azo dye-metal complexes with alpha cyclodextrin, they observed two kinetic processes. The dependence of the observed rate-constants for these two processes on the alpha cyclodextrin concentration was found to be explainable in terms of a mechanism identical to that proposed earlier by Hersey and Robinson. In the case of the guests used by Seiyama and coworkers, however, values for the rate constants of the binding step could be determined from the concentration dependence of kobs for the faster process thus,... 

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. 

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