Synthesis and solvatochromic properties of some disazo dyes derived from pyrazolo[1,5-a]pyrimidine derivatives

4-Arylazo-3,5-diaminopyrazole compounds have been synthesized by reaction of arylazomalononitrile with hydrazine hydrate. The symmetrical and asymmetrical 3,6-diarylazo-2,5,7-triaminopyrazolo[1,5-a]pyrimidine heterocyclic disazo dyes have been prepared by the cyclization of 4-arylazo-3,5-diaminopyrazoles with different arylazomalononitriles. The solvatochromic behaviour of these disazo dyes in various solvents was evaluated.