DFT and¹H NMR molecular spectroscopic studies on biologically anti-oxidant active paramagnetic lanthanide(III)-chrysin complexes

Abstract

The interaction of trivalent lanthanide chlorides and chrysin in methanol results in formation of the complexes [Ln(chrysin) 3 ], where Ln ¼ 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. 1 H NMR spectra of lanthanum, praseodymium, neodymium, samarium and gadolinium complexes have been studied in DMSO-d 6 . 1 H 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.

Synthesis of Cr(III)-Morin Complex: Characterization and Antioxidant Study

“…The differences in the relative broadening reflect the different metal-proton distances, the broader peaks being associated with the proton nuclei of the ligand closer to the metal ion and these broad resonances support the octahedral geometry of the complex. These observances suggest that aromatic ring coordinates to the metal ion through phenolic and carbonyl groups [ 33 ].…”

Synthesis and evaluation of antioxidant and antibacterial properties of morin complexes

“…IR data obtained from spectra of morin and its Mg(II) and Ca(II) complexes is in accord with the structure. From significant shifts in the absorbance frequencies of metal morin complexes it may be presumed that morin is coordinated [3,39].…”

“…Finally, the contents were washed with t-butanol, dried in a vacuum dessicator and the yield calculated as 73% and 85% for Mg and Ca complexes of morin, respectively. Elemental analysis found (%): C, 39 …”

Properties and applications of flavonoid metal complexes

“…36,45,[53][54][55] However, for steric reasons, complexes with more than two avonoid ligands are usually restricted to rare-earth metal ions. [55][56][57][58][59] It should be noted that the simultaneous binding of two metal ions to the 3-4 and 4-5 site is unfavorable because of steric repulsion.…”