Synthesis, characterization, kinetics, thermodynamics and nematicidal studies of Sm(III), Gd(III) and Nd(III) Schiff Base Complexes

Abstract

Schiff base derived from benzaldehyde and ethylenediimine and its Sm(III), Gd(III) and Nd(III) complexes were synthesized. The ligand N, N’-Bis(2-hydroxy-1,2-diphenylethanone)ethylenediamine (N, N'- B2HDE) and its complexes were characterized by molar conductivity, melting point, solubility test and spectrophotometrically (IR and UV-Vis). The kinetics was studied by determining the rate of formation at different temperatures. The observed rate constants k was obtained and used to obtain activation energy (Ea). Thermodynamics parameters showed that activation energy (Ea) obtained for Sm(III) and Gd(III) was 0.452, and 1.196 KJ respectively which were positive (Ea) indicating that, the rate of formation increased with increased temperature. The result of thermodynamic parameters showed that; the ΔG^o of the complexes were -3896.02 KJmol^-1and - 8201.18KJmol ¹ which indicated the ability of the studied ligand to form stable complexes, while ΔH^o was 1168 KJmol^-1 and 2268 KJmol^-1, for Sm(III) and Gd(III) respectively. The negative result of the ΔS^o of Sm(III) and Gd(III) was -16.99 KJmol^-1 and -19.91 KJmol^-1respectively. The ligand and its metal complexes were screened for nematicidal activities against a root knot nematode, Meloidogyne incognita. The metal complexes revealed better nematicidal activities than ligand. The solubility showed that ligand and its metal complexes were electrolytic nature, soluble in acetone, dimethylsulphoxide, dimethylformaldehyde while the melting point of ligand and complexes was found to be between 120-130 ^oC. The complexes had molar conductivity of 11.5-12.0 indicating an electrolytic property; The IR spectra coordinated through azomethine nitrogen atom and hydroxyl group. UV-Vis spectrophotometer showed a complexation of the metal and ligand, demonstrating an octahedral geometry for both complexes. Hatching test of the ligand and its metal complexes showed that they behaved radically different from each other. The behaviour of the ligand and its complexes at different time (hours) and concentrations employed showed significant difference in terms of their nematicidal activity against M.
incognita.