Microwave synthesis, characterization, and bio-efficacy of novel halogenated Schiff bases

Abstract

ABSTRACTA new series of halogenated Schiff bases was synthesized by the condensation of 5-fluoro-2-hydroxy acetophenone and 3,5-dichloro-2-hydroxy acetophenone with different alkyl amines, namely propyl, pentyl, hexyl, heptyl, octyl, nonyl, dodecyl, tetradecyl, hexadecyl, and octadecyl amines, under microwave irradiation. Newly formed molecules were characterized by Infrared and nuclear magnetic resonance (1H NMR and 13C NMR) spectroscopic techniques. Further, the Schiff bases were screened for antifungal bioassay, and the results showed potential fungicidal activity against two very important plant infecting fungi, viz. Rhizoctonia solani and Sclerotium rolfsii. Among the screened compounds, 2,4-dichloro-2-[1-(propylimino)ethyl]phenol was found to be the most active compound against both R. solani (ED50 8.02 mg L−1) and S. rolfsii (ED50 21.51 mg L−1) followed by 2,4-dichloro-2-[1-(pentylimino) ethyl]phenol (ED50 13.02 and 29.57 mg L−1, respectively). The synthesized compounds were also screened for antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH)-free radical scavenging technique. All the compounds showed very low to moderate activity as compared with Gallic acid.