New phenylhydrazinium complexes of lanthanide (III) with ethylenediaminetetraacetate: Spectral, thermal and XRD studies

R. Ragul and B. N. Sivasankar

Abstract

Synthesis, structural characterization and thermal degradation studies on novel precursors, phenyl hydrazinium lanthanum (III) ethylenediaminetetraacetate hydrates, PhNHNH3[Ln(EDTA)(H2O)2](H2O)3 where Ln= La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy to potential binuclear μ-hydroxo clusters are reported. The conductivity measurements reveal that the phenyl hydrazinium part, PhNHNH3 + is ionic and outside the coordination spheres. The infrared spectra shows the presence of both coordinated and lattice water molecules and characteristic bands for ethylenediaminetetraacetate moiety along with the N-N stretching for non coordinated phenyl hydrazinium ion. The simultaneous TG-DTA experiments in air reveal the presence of two coordinated and three lattice water molecules. All the complexes undergo multi-step degradation to yield respective oxides and Ln2O3 as the final residue. The metal analyses, infrared spectra and X-ray powder technique have been used to confirm the end product. The X-ray diffraction patterns of the complexes are in accordance with the isomorphism among the series. Due to the presence of several unpaired electrons and large size of lanthanide (III) ions, these complexes are expected to possess antioxidantal properties. Among the lanthanide complexes praseodymium complex shows maximum activity and the gadolinium complex shows poor activity. However, the free radical quenching powers of other complexes depend on the number of unpaired electrons in the respective rare earth metal ion.