Synthesis, Spectroscopic Characterization and Antimicrobial Activities of Some Rare Earth Metal Complexes of Biologically Active Asymmetrical Tetradentate Ligand

The solid complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III) and Gd(III) with asymmetrical tetradentate Schiff bases derived from 4-methyl-o-phenylenediamine, 3-Acetyl-6-methyl-pyran-2,4-dione and 2-hydroxy-1-naphthaldehyde have been synthesized and characterized by elemental analysis, conductometry, magnetic susceptibility, UV-visible, FTIR, 1 H-NMR spectra, X- ray diffraction, thermal analysis and screened for antimicrobial activity. The IR spectral data suggest that the ligand behaves as a dibasic tetradentate ligand with ONNO donor atoms sequence towards central metal ion. From the microanalytical data, the stoichiometry of the complexes has been found to be 1:1 (metal: ligand). The X-ray differaction data suggest tetragonal crystal system for La(III) complex and orthomboic crystal system for Ce(III) complex. Thermal behaviour (DSC/TGA) of the complexes was studied and kintic parameters were determined by Horowitz-Metzger and Coats-Redfern method. The ligand and their metal complexes were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli and fungicidal activity were tested against Aspergillus Niger and Trichoderma.