The synthesis, spectroscopic properties and theoretical calculation of some novel disperse disazo dyes derived from 3-amino-5-hydroxy-1-phenylpyrazole

In this study 5-amino-4-arylazo-3-methyl-1H-pyrazoles (1a-1m) were diazotised and coupled with 3amino-5-hydroxy-1-phenylpyrazole to give disperse disazo dyes (2a-2m). The newly synthesized 13 disperse disazo dyes were characterized by elemental analysis and spectral methods. The solvatochromic behaviour of these disperse disazo dyes in various solvents was evaluated. Substituent, acid and base effects on the visible absorption spectra of the disperse disazo dyes substituted with electron-withdrawing and electron-donating groups at their o-, m-, p-position were also reported in detail. Additionally, theoretical calculations are performed for the disazo dyes. The molecular geometry and chemical shift are calculated by using ab initio calculations based on the density functional theory (DFT) in the ground state. The results obtained are in agreement with the experimental results. (C) 2009 Elsevier B.V. All rights reserved.