Synthesis, Structure, Antioxidant, and Antiviral Studies on N₂H₅[Ln(edta)(H₂O)₃].5H₂O (Ln = Pr, Nd, and Sm)

Abstract

Single crystals of N₂H₅[Ln(edta)(H₂O)₃].5H₂O (Ln = Pr, Nd and Sm) have been prepared and the molecular structures of these crystals were determined by X-ray single crystal study. The X-ray powder diffraction patterns of the three complexes reveal that they are isomorphous. These complexes are nine coordinated with a hexadentate edta⁴⁻ ion and three coordinated water molecules. However, the remaining five more water molecules present as lattice water. Hydrazinium cation, though capable of coordination with the metal ion, in the present case present outside the coordination sphere as primary valency. The Ln(III)N₂O₄O′₃ parts in the complex anions have the same structures in all the three complexes. The crystals of Pr(III), Nd(III), and Sm(III) complexes belong to the orthorhombic crystal system and Fdd2 space group. The crystal data are as follows: Pr(III): a = 19.6712(5) Å, b = 35.6939(9) Å, c = 12.3079(4) Å, α = β = γ = 90°, V = 8641.9(4) ų, R = 0.0255, and Rw = 0.0728 for I>2σ (I) and 10119 reflections. Nd(III): a = 19.6414(3) Å, b = 35.6177(5) Å, c = 12.3212(2) Å, α = β = γ = 90°, V = 8619.7(2) ų, R = 0.0251, and Rw = 0.0693 for I > 2σ (I) and 7378 reflections. Sm(III): a = 19.5814(3) Å, b = 35.4617(7) Å, c = 12.2931(2) Å, α = β = γ = 90°, V = 8536.2(3) ų, R = 0.0233, and Rw = 0.0641 for I > 2σ (I) and 6766 reflections. These complexes show promising antioxidant activity as expected for lanthanide(III) ions with unpaired electrons. The antiviral screening also shows enhanced activities of these complexes than the respective non-hydrazinium and ammonium chelates. The crystals of the complexes in purest form were powdered and subjected to constant temperature degradation at 600°C to yield pure fine powders of the respective oxides. The microstructures of the oxides were studied by scanning electron microscope photographs.

Keywords:

• antioxidant
• antiviral
• edta
• hexadentate
• hydrazinium
• lanthanide(III) ions
• nine coordination

Acknowledgments

The authors sincerely thank UGC for financial assistance in the form of minor research project and IIT –Madras, Chennai, for recording X-ray diffraction data.