Pseudo Sulfur Dyes

The term pseudo (or synthetic) sulfur dyes refers to dyes that have application properties similar to those of sulfur dyes but are obtained by the insertion of mer-capto groups or their precursors into the dye precursors or pigments rather than by the classical sulfurization method. These dyes thus have some of the characteristics of sulfur dyes. 

The principal chromophores in pseudo sulfur dyes are copper and cobalt phthalocyanines, e.g., in C.I. Sulphur Green 25 (16), and the perylene tetracar-boxylic diimide structure in C.I. Sulphur Red 14 [81209-07-6] and C.I. Solubilised Sulfur Red 11 [61969-41-3] (17). In contrast to the sulfur dye made from Cu phthalocyanine, the cobalt derivative can be applied with dithionite. 

Some special reactive dyes that can be applied by sulfur-dye methods and can also be combined with sulfur dyes represent a special case. An example is C.I. Solubilised Sulfur Red 11. These dyes contain no thiolate groups at all. 

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Pseudo sulfur dyes are dyes that can be applied in the same way as sulfur dyes but are not prepared by classical sulfurization. 

Pseudo sulfur dyes are not prepared by the classical sulfurization method. Instead, mercapto groups or their precursors are introduced into dye precursors or pigments by preparative means. 

Pseudo-stilbenes may emit fluorescence that is, contrary to true stilbenes, generally weak at room temperature and often weak even at low temperatures. Protonated azobenzene-type molecules and many protonated azo dye molecules emit strong fluorescence in sulfuric acid at 77 K with quantum yields of about 0.1. Inclusion of azobenzene in the channels of AIPO4-5 crystals provides complexation of the n-electrons and space confinement. This leads to emission by protonated azobenzene at room temperature. For their cyclopalladated azobenzenes, Ghedini et al. " report quantum yields of ca. 1T0 and lifetimes of ca. 1 ns. In contrast, donor/acceptor pseudo-stilbenes, if emitting at low temperatures or when adsorbed to surfaces, are weak emitters. In textile chemistry, it has long been known that azo dyes adsorbed to fibers may show fluorescence. ... 

Pseudo-stilbenes may emit fluorescence that is, contrary to true stilbenes, generally weak at room temperature and often weak even at low temperatures. Protonated azobenzene-type molecules and many protonated azo dye molecules emit strong fluorescence in sulfuric acid at 77 with quantum... 

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