Synthesis, characterization and antibacterial study of 5-substituted 1,10-phenanthroline-2,9-dialdehydes and their Schiff bases with sulfur-containing amines
The use of chelating agent such as 1,10-phenanthroline (phen) has played an important role in synthetic and medicinal chemistry. 1,10-phenanthroline (phen) has several distinct properties due to the rigid structure and an interesting synthon in the synthesis of numerous multifunctional molecules. Also, phenanthroline derivatives containing O, S, N atoms have received considerable attention because of their pharmacological properties like anticancer, antibacterial, antitumor activity. 2,9-dialdehyde-1,10-phenantroline Schiff base ligands provide suitable conformational and coordination environments for the metal ions. This property has made them important in different areas like self-assembly, coordination chemistry, catalysis etc. Hard `nitrogen' and soft `sulfur' donor atom containing Schiff bases are synthesized from S-alkyl/aryl dithiocarbazaic acid with heterocyclic aldehydes and ketones which are able to form stable complexes with a variety of metal ions. To synthesize Schiff base having the above mentioned properties 1,10-phenanthroline-2,9-dicarboxaldehyde and sulfur containing amines were taken and studied their antibacterial properties. Eight new Schiff bases of 5-nitro and 5-bromo-substituted 1,10-phenanthroline-2,9-dicarboxaldehydes with the sulfur-containing amines, thiosemicarbazide, S-alkyl/aryl dithiocarbazates and 2-mercaptoaniline have been synthesized and characterized by a variety of spectroscopic methods. The condensation reactions of the dialdehydes with the amines were carried out both in the presence and absence of conc. sulfuric acid. A significant increase in yield of the Schiff bases was observed when the reactions were carried out in the presence of sulfuric acid. These Schiff bases and intermediates compounds were used for antibacterial study. The antibacterial activity of the synthesized compounds was initially examined by paper disc diffusion technique. Also, the minimum inhibitory concentrations (MIC) of these compounds were determined by tube dilution method. All the compounds showed antibacterial activity at the tested dose against different human and plant pathogenic bacteria. But, for most compounds activity was considerably less when compared to the reference standard drug tetracycline. However, one intermediate compound showed very high activity against some human and plant pathogenic bacteria, even sometimes higher active than standard tetracycline.
"Synthesis, characterization and antibacterial study of 5-substituted 1,10-phenanthroline-2,9-dialdehydes and their Schiff bases with sulfur-containing amines"
ETD Collection for Tennessee State University.