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

摘要

Nine coordinated [Ln(quercetin)_3]nH_2Ocomplexes were synthesized in non-aqueous solution(where, n =0 for Pr, Sm, Gd, Tb, Dy and Ho; n = 3, for La and Nd). The complexes werecharacterized by elemental analysis, molar conductance, UV –vis spectra, IR spectra,thermal analysis and NMR spectra. The optimized structures of the complexes wereobtained by molecular modeling. The complexes behave as non-electrolytes in DMSO. TGAstudy showed anhydrous nature of the complexes (except La and Nd). The 'H NMR spectraof lanthanum, praseodymium, neodymium and samarium complexes have been studied inDMSO-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 loweras well as higher field shifts that show change in geometry during the metal ligandcoordination.