As a part of our ongoing interest in disperse dyes and task specific azo dyes with better dyeing properties, we synthesized a series of 3-aryl(hetaryl)hydrazono-2,4-chromandiones 4a-k via Coupling of 4-hydroxycoumarin with diazotized aniline derivatives. Structures of the synthesized compounds have been investigated by means of UV, IR, 1 H-NMR and mass spectroscopy in order to elucidate their tautomeric and isomeric structures. The results of such spectral data indicated that compounds 4a-k exist predominantly in the hydrazo structure (D) as a mixture of Z and E-isomer with ratio ~ 84.5:15.5. Finally, the prepared dyestuffs 4a-k were applied as disperse dyes for dyeing polyester fabrics and their fastness properties were evaluated. Also, the position of color in CIELAB coordinates

The main target of this paper was the synthesis of novel azo disperse dyes with better dyeing properties, together with a systematic investigation to determine their dominant tautomer(s) from 12 possible tautomeric structures. In this regard, novel azopyrazolin‐5‐one dyes were synthesised via the reaction of hydrazine hydrate with 2,3,4‐chromantrione‐3‐arylhydrazones. The acid dissociation constants both in the ground and in the excited state for the series prepared were determined and correlated by the Hammett equation. The results of this correlation, together with spectral data, indicated that the compounds under scrutiny exist predominantly in the keto‐hydrazo structure as a Z‐configuration, both in the ground and in the excited state. Finally, the synthesised dyes were applied as disperse dyes for dyeing polyester fabrics, and their fastness properties were evaluated. Also, the position of colour in CIELAB coordinates was estimated and discussed.

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