Synthesis of new pyrazolone dyes

New azo- and bisazo-5-pyrazolone dyes have been synthesised by azo coupling of various arylamines and aryl diamines with 5-pyrazolones: 1-methyl-3-phenyl-1H-pyrazol-5(4H)-one, 1-(4-chlorophenyl)-3-isopropyl-1H-pyrazol-5(4H)-one and 3-isopropyl-1-(4-methoxyphenyl)-1H-pyrazol-5(4H)-one, respectively. All new synthesised dyes have been characterised by FTIR, H-1, C-13 NMR and UV-Vis spectral studies with GC/MS and LC/MS analyses. FTIR and H-1 NMR studies confirmed the existence of azo- and hydrazo-tautomeric forms of the dyes in the solid and liquid states, respectively.