¹H NMR, spectroscopic and molecular modeling studies on paramagnetic lanthanide(III)-quercetin complexes

Abstract

Nine coordinated [Ln(quercetin) 3 ]nH 2 O complexes were synthesized in non-aqueous solution (where, n ¼ 0 for Pr, Sm, Gd, Tb, Dy and Ho; n ¼ 3, for La and Nd). The complexes were characterized by elemental analysis, molar conductance, UV -vis spectra, IR spectra, thermal analysis and NMR spectra. The optimized structures of the complexes were obtained by molecular modeling. The complexes behave as non-electrolytes in DMSO. TGA study showed anhydrous nature of the complexes (except La and Nd). The 1 H NMR spectra of lanthanum, praseodymium, neodymium and samarium complexes have been studied in DMSO-d 6 . The complexes do not dissociate in DMSO and retain their coordination number. The NMR spectra of paramagnetic and diamagnetic complexes of quercetin exhibit lower as well as higher field shifts that show change in geometry during the metal ligand coordination.

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.…”

Complexation of rare earth metals by quercetin and quercetin-5’-sulfonic acid in acidic aqueous solution

“…Moreover, quercetin can effectively chelate metal ions [12]. In literature describe solid complexes of quercetin with alkali [13], transition [13,14], rare earth [15] and noble [16,17] metals. Research linked to study of aqueous complexation between quercetin and La [18], Fe [19], Pb [20] has been demonstrated difficult behavior of current ligand.…”

Synthesis and Structural Investigation of New Bio-Relevant Complexes of Lanthanides with 5-Hydroxyflavone: DNA Binding and Protein Interaction Studies

“…Studies of the interaction between some lanthanide ions and flavonoid molecules led to the isolation and characterization of solid complexes derived from chrysin, Ln(C 15 H 9 O 4 ) 3 ·4H 2 O (where: C 15 H 9 O 4 is deprotonated chrysin) [9], [Ln(chrysin) 3 ] [10], [LnL 2 (H 2 O) 2 Cl] (L: chrysin) [11], quercetin, [Ln(quercetin) 3 ]· n H 2 O [12], or morin, Ln(morin) 3 [13], Ln(C 15 H 9 O 7 ) 3 · n H 2 O, where n = 6 or 8, C 15 H 9 O 7 = morin [14,15].…”