The Role of Anthraquinonoid Dyes in the Catalytic Fading'of Dye Mixtures– Substituent–dependent Triplet Yield of Diaminoanthraquinones

Taking various diaminoanthraquinones as model compounds for commercial anthraquinonoid dyes it was found that the ability of initiating catalytic fading via singlet oxygen mechanism is closely related to the quantum yield of triplet formation in these dyes. The quantum yields of triplet formation show a marked difference between the various diaminoanthraquinones. Whereas 1, 4– and 1, 2–diaminoanthraquinones have very small quantum yields, the 1, 5– and 1, 8–derivatives pass into the triplet state with a fairly high efficiency. From this it was concluded that catalytic fading occuring via singlet oxygen mechanism must be expected in dye mixtures consisting of 1, 5– or 1, 8–diamino substituted anthraquinonoid dyes and easily oxidizable azo–compounds.