Pigment & Resin Technology

Purpose – The purpose of this paper is to synthesise, characterise and find out properties of some new bifunctional reactive azo dyes using pyrazolo[1,2-a]pyrazole 3-carboxylic acid fused systems as the chromophoric moiety, bearing good colour strength, lightfastness, and other favourable properties.

Design/methodology/approach – The dyes are synthesised by diazotisation, coupling and cyclisation reactions. Firstly, synthesised 4-arylazo-1,5-dioxopyrazolo[1,2-a]pyrazole 3-carboxylic acid chromophoric moieties and coupled with diazonium salts having the aforementioned reactive groups, thus yielding the new target reactive. The synthesised dyes were applied to cotton and wool fabrics under the typical exhaust dyeing conditions and their dyeing properties were investigated. The structures of these dyes are characterised and confirmed by melting point, elemental analysis, infrared, ultraviolet-visible spectroscopy (UV/VIS) and nuclear magnetic resonance (1H-NMR) data.

Findings – The wavelength of maximum absorptions, molar extinction coefficients are strongly dependent on the electron donating ability of the substituents on the coupling moiety. The absorption bands of these dyes move towards longer wavelength as the polarity of the solvents and electron density of substituents on the coupling moiety increase. The dyes applied on cotton and wool showed higher exhaustion and fixation values, colour yields and fastness properties.

Research limitations/implications – The method developed provided a simple producing fused pyrazolo[1,2-a]pyrazole disazo chromophoric systems based on 4-arylazo-1,5-dioxopyrazolo[1,2-a]pyrazole 3-carboxylic acid as well as reactive dyes applied on wool and cotton dyes.

Originality/value – In this paper, three series of pyrazolo[1,2-a]pyrazole derivatives dyes are synthesised and characterised. They have not been registered in the literature previously.