Synthesis, physical properties and spectroscopic studies of oxamato (−1) lanthanide(III) complexes

Abstract

New complexes of the general formulae Ln(Hoxm) 3 · 2H 2O (Ln ≡ La, Ce, Pr, Nd, Gd), Ln(Hoxm) 3 · 3H 2O (Ln ≡ Sm, Eu, Tb, Dy, Ho, Er) and Yb(Hoxm) 3 · H 2O, where H 2 oxm = oxamic acid, have been prepared. The complexes were characterized by means of elemental analyses, conductivity measurements, thermal methods (TG, DTG, DTA, DSC), X-ray powder patterns, magnetic moments and spectroscopic studies (IR, Raman, 1H-NMR, electronic diffuse reflectance and emission f-f spectra). The neutral primary amide group of Hoxm − is not coordinated to the metal ions. The carboxylate groups exhibit two different types of bidentate coordination in the complexes of lanthanum(III), cerium(III), praseodymium (III) and neodymium(III), while the presence of both monodentate and bidentate carboxylato donor groups is assigned for the other compounds. All the data are discussed in terms of the nature of the bonding and the possible structural types. The anhydrous species obtained by thermal decomposition of the initially isolated complexes are also studied.