1.1.4. Synthesis and characterization of some sulfadrugs azodyes, potentiometric studies of the synthesized dyes and their Fe (III) complexes.

New sulfa drugs azo dyes (HL1, HL2, HL3, HL4 and HL5) were prepared by the coupling of 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one with the sulfa drugs (sulfadiazine, sulfapyridine, sulfamethoxazole, sulfadimidine, sulfathiazole). The five prepared ligands were characterized by elemental analysis, infrared, mass spectra, and 1H-NMR spectra. The ionization constants of the ligands and stability constants of their Fe (III) complexes were determined potentiometrically in ethanol-water media at 25°C. HL1 ligand has two pKa values while the other ligands (HL2, HL3, HL4 and HL5) have one pKa value. All the ligands form 1:1 metal chelates