Cationic dyes delocalized

The positive charge of cationic dyes may be either localized or delocalized. In 1, the positive charge is localized on an ammonium group ... 

Cationic dyes with delocalized charge are classified with the methine dyes (see Section 2.6). They may be viewed as vinylogous amidinium salts 3 [1] ... 

Cationic dyes form positively charged dye ions by dissociation, and the positive electric charge is delocalized over the entire molecule. They are usually di- and triarylmethine dyes such as C.I. Basic Green 4, 42000 [569-64-2] (31), which are also known as triarylmethane dyes or triaryl carbenium ions [15], oxazine dyes such as C.I. Basic Blue 3, 51005 [2787-91-9] (32), orthiazine dyes. 

The positive charge is here an integral part of the chromophoric system and the dyes are termed delocalized cationic dyes. 

So-called delocalized cationic azo dyes are another type ia which the positive charge is delocalized (or distributed) across the dye cation. Basic Blue 54 (132) (2-amiao-6-methoxybenzothiazole coupled to /V, /V-dimethy1 ani1 ine and then quarternized with dimethyl sulfate) is an example of this class which can also be considered as a diazamethine dye. 

Basic Red 22 (134), which contains 1 part ia 7 of the yellowish red 1,4-dimethyl isomer, Basic Red 29 (135), and Basic Yellow 25 (136) are all examples of delocalized cationic azo dyes. Dyes of this type can also be synthesized by Hbnig s oxidative coupling reaction of heteroaromatic hydrazones with tertiary aromatic amines. 

Delivery receipt, 25 330 Delocalized cationic azo dyes, 9 423 Delta-3-carene (A-3-carene), 24 499 8-alumina, 2 404, 406t Delta coke, 22 704 8-damascone, 24 570... 

In the diazahemicyanine dye 2, the positive charge is delocalized across the dye cation. 

Such bonding implies that chelation of the proton with the azo group increases the accessibility of the electron pair involved in the hydrogen bond with the cotton. The chelation of a metal ion would probably result in the formation of a more stable chelate ring but would also introduce the probability of delocalizing the electron pair as well as converting the dye to a cation. 

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