Synthesis, Characterization, and Theoretical Calculation of New Azo Dyes Derived from [1,5-a]Pyrimidine-5-one Having Solvatochromic Properties

Abstract

7-Amino-3-phenylazo-2-methyl-4H-pyrazolo[1,5-a]pyrimidine-5-one (3) was synthesized by the reaction of 5-amino-3-methyl-4-phenylazo-1H-pyrazole and 2-aminobenzothiazole with ethyl cyanoacetate in acetic acid at 150°C. Four novel heterocyclic azo disperse dyes were obtained by the coupling of heterocyclic amines-based diazonium chloride with compound 3. They were purified and characterized by elemental analysis, FTIR, and 1 H NMR. Furthermore, solvatochromic behaviors of related dyes were studied in detail by using ultraviolet–visible absorption spectrometer. The experimental data were supported by density functional theory using b3lyp/cc-pvtz level calculations, and a detailed analysis of predicted tautomeric structures was made.