I. Manolov et al., Cytotoxic activity of cerium complexes with coumarin derivatives. Molecular modeling of the ligands, ARCH PHARM, 333(4), 2000, pp. 93-98
Cerium complexes of Umbellipherone, Mendiaxon, Warfarin, Coumachlor. and Ni
ffcoumar have been synthesized by reaction of the ligands with cerium nitra
te in a stoichiometric ratio of 1:2. The formation of the complexes has bee
n proved on the basis of elemental analysis, conductivities, IR spectroscop
y, and H-1-NMR spectroscopy. The molecules of the ligands were optimized by
means of the semiempirical quantum mechanical method PM3 to the energetica
lly most stable conformers. All the ligands were characterized by molecular
and submolecular electronic indices and the putative donor centers are pro
posed. It is concluded that the lactone- and the keto-carbonyl groups of Wa
rfarin, Coumachlor, and Niffcoumar are bonded to the metal ion as bidentate
ligands. The other two coumarins are bonded as monodentate ligands. Conduc
tivity measurements show the non-electrolytic nature of the complexes. Cyto
toxic screening by MTT assay was carried out. The cerium complexes were fou
nd to be more active than the inorganic salts.