Synthesis, Characterisation and Colorimetric Study of New Azo-stilbene Dyes

Using 4,4\'-diaminostilbene-2,2\'-disulphonic acid an well known eco-friendly middle component and 2-chlorosalicylanilide and 2-bromosalicylanilide as coupling components, two new symmetrical disazo direct dyes were synthesized. The dyes were analyzed by TLC, VIS, FT/IR, ¹³C-NMR spectroscopy, and HPLC technique. The colour assessment of the two new synthesized dyes was made by means of the tri-stimulus colour characteristics lightness (L*), redness (a*), yellowness (b*), chroma (C*) and hue angle (hº) relative to the standard illuminants: D65 (natural day light), A (tungsten light), F2 (fluorescent light) and the standard 10° observer respectively The colour differences (ΔE_ab^*, ΔECMC) calculated against an white standard, namely Pigment White 6 (C.I. 77 891) reveal a good colouring power of these new azo-stilbene dyes