SYNTHESIS, CHARACTERIZATION AND ANTIMICROBIAL STUDY OF RARE EARTH COMPLEXES OF SCHIFF BASE DERIVED FROM 4-AMINO-3-HYDROXY BENZOIC ACID

Schiff base was prepared by using 4-amino-3-hydroxy benzoic acid and 4-nitrobenzaldehyde, namely (E)-3-hydroxy-4-((4-nitrobenzylidene) amino)benzoic acid. In the preparation of rare earth complexes, nitrates of lanthanum, Cerium, and Praseodymium were used with Schiff base. Rare earth Schiff base complexes were prepared by using NaOH to maintain the pH of solvent. Synthesized Schiff base ligand and its complexes were structurally characterized by UV, IR, NMR, HRMS, TGA, and elemental analysis. Structural characterization shows 1:2 metal to ligand ratio in the complexes. The electronic absorption spectra of the ligands and their metal complexes are recorded after preparing the solution and after standing the solution for 3 weeks in DMF. No appreciable change was observed in the spectrum with time. Free ligands and their metal complexes have different electronic spectra’s and blue shift observed in complexes which support the complex formation. HRMS are in good agreement with calculated values, which confirms the proposed structure of ligand. Carboxylate group of Schiff base ligand shows bidentate the coordination to central metal and azomethine group is not involved in coordination. TGA shows the presence of lattice and coordinated water molecules in complexes. The present study deals with antibacterial and antifungal activity of Schiff base ligand and their Ln(III) complexes by disc diffusion method. In the study of antibacterial activity of the free Schiff base ligand and their Ln(III) complexes were screened in-vitro against gram-positive bacteria Staphylococcus aureus and Bacillus subtilis as well as with gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa with Chloramphenicol as standard drug. In the study of antifungal activity of the free Schiff base ligand and their Ln(III) complexes were screened in-vitro against Aspergillus niger and Saccharomyces cerevisiae with Amphotericin B as a standard drug. Schiff base ligand and complexes showed good antimicrobial activity against Saccharomyces cerevisiae.