Structural, thermal, morphological and biological studies of proton-transfer complexes formed from 4-aminoantipyrine with quinol and picric acid.

4-Aminoantipyrine (4AAP) is widely used in the pharmaceutical industry, biochemical experiments and environmental monitoring. However, residual amounts of 4AAP in the environment may pose a threat to human health. To provide basic data that can be used to extract or eliminate 4AAP from the environment, the proton-transfer complexes of 4AAP with quinol (QL) and picric acid (PA) were synthesized and spectroscopically investigated. The interactions afforded two new proton-transfer salts named 1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-aminium-4-hydroxyphenolate and 1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-aminium-2,4,6-trinitrophenolate for QL and PA, respectively, via a 1:1 stoichiometry. Elemental analysis (CHN), electronic absorption, spectrophotometric titration, IR, Raman, (1)H NMR and X-ray diffraction were used to characterize the new products. The thermal stability of the synthesized CT complexes was investigated using thermogravimetric (TG) analyses, and the morphology and particle size of these complexes were obtained from scanning electron microscopy (SEM). It was found that PA and 4AAP immediately formed a yellow precipitate with a remarkable sponge-like morphology and good thermal stability up to 180°C. Finally, the biological activities of the newly synthesized CT complexes were tested for their antibacterial and antifungal activities. The results indicated that the [(4AAP)(QL)] complex exhibited strong antimicrobial activities against various bacterial and fungal strains compared with standard drugs.