Synthesis and absorption spectra of some novel heterocyclic disazo dyes derived from pyridone and pyrazolone derivatives

Heterocyclic amines were diazotized and coupled with 3-aminocrotononitrile to give the 2-hetarylhydrazone-3-ketiminobutyronitrile (1a–1e) which can react with hydrazine hydrate and phenylhydrazine to afford the corresponding 5-amino-3-methyl-4-hetarylazo-1H-pyrazoles and 5-amino-3-methyl-4-hetarylazo-1-phenylpyrazoles (2a–2j), respectively. Then, some novel disazo dyes 3a–3j and 4a–4j were synthesized by diazotisation of 5-amino-3-methyl-4-hetarylazo-1H-pyrazoles and 5-amino-3-methyl-4-hetarylazo-1-phenylpyrazoles using nitrosyl sulphuric acid, coupling with 3-cyano-6-hydroxy-4-methyl-2-pyridone and 3-methyl-1H-pyrazole-5-one. The dyes were characterized by elemental analysis and spectral methods and the solvatochromic behaviour of the dyes in various solvents was evaluated. Substituent, acid and base effects on the visible absorption maxima of the dyes were also reported.