DFT and H-1 NMR molecular spectroscopic studies on biologically anti-oxidant active paramagnetic lanthanide(III)-chrysin complexes

摘要

The interaction of trivalent lanthanide chlorides and chrysin in methanol results in formation of the complexes [Ln(chrysin)3], where Ln = La, Pr, Nd, Sm, Gd, Tb and Ho. The complexes have been characterized by elemental analyses, molar conductance, IR, UV–Vis, TGA/DTA and NMR spectroscopic studies. They behave as non-electrolytes in DMF solution. The TGA data indicated that the complexes were anhydrous. The electronic spectra of the complexes were recorded in methanol DMF and DMSO solutions. 1H NMR spectra of lanthanum, praseodymium, neodymium, samarium and gadolinium complexes have been studied in DMSO-d6. 1H NMR spectra of paramagnetic and diamagnetic complexes exhibit down-field as well as up-field shifts of chrysin resonances that shows a change in geometry during the ligand coordination to the metal ion. A theoretical study of the chrysin molecule was conducted through DFT, ab initio, and AM1 methods and this determined the coordination environment of the metal ions.