Synthesis And Antibacterial Studies Of Asymmetric Di-Schiff Bases

Schiff base compounds have aroused widespread attention for a long time because of their widespread app1ications in medicine, catalysis, chemical analysis, functional materials, corrosion resistance, activity of oxygen carrier and so on, which is mainly due to the funtionality of C=N and the electron effect. So the studies of synthesis and properties for the compund also have become a quite active subject in chemistry fields in recent decades.The synthesis and exploratory development of schiff bases were summarized in this paper and their synthesis, character and antibacterial activity were also investigated. In the synthesis part, with raw materials of 2-methyl benzoic acid and p-Xphenol(X=Br,Cl), 2-{[(2-aminophenyl)imino](o-tolyl)methyl}-4-Xphenol was obtai -ned by esterification, fries rearrangement, condensation and so on. The mono-schiff base reacted with ten aldehydes, such as salicylaldehyde, p-dimethyl aminobenzaldehy -de, 2-thiophenecarboxaldehyde, benzaldehyde, 2,4-dihydroxy aceto-phenone, o-dihydroxy acetophenone and so on in different conditions. Thereby twenty asymmetrical di-schiff bases were given. Structures of products were characterized by NMR and melting point. Then reactive processes and mechanisms were presumed on the basis of these structures.The study on antibaterial activity of schiff bases was carried out by filter paper method. Two representative strains, Gram-negative bacterium (E. coli) and Gram- positive bacterium (S. aureus) were selected. Their antimicrobial activity was determined by measurement for zone of inhibition. It was detected in multiple controlled trials that minimum inhibitory concentration (MIC) of compunds were determined and the regularity was summarized according to the size of zone of inhibition. Results showed that most of ligands have the activity of inhibiting the growth of two bacterium, certain selectivity to strains and inhibition is weaker to E. coli′than S. aureus′.Besides, the same substituent in different positions may leads to different results of antibacterial activity. The schiff base with S atom in the molecule has highest antimicrobial activity. The MIC is 10^-4g·L^-1 for Gram-positive bacterium (S. aureus) and 10^-3g·L^-1 for Gram-negative bacterium (E. coli).