Magnetism of the lanthanides(III) complexes with some polihydroxyflavones

The La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III) and Lu(III) ions form solid complexes with morin and quercetin-5′-sulfonic acid (QSA). The composition and some physicochemical properties of these compounds were described previously. In order to estimate magnetic properties, the oxidation number of metal ions and the nature of the metal–ligand bonding in the investigated rare earth element complexes the magnetic measurements were carried out. On the basis of the magnetic susceptibility (χ) versus T and the magnetic moments (μeff) versus T the values of Curie (C) and Weiss (Θ) constants for all examined compounds were determined. Moreover, for Sm(III) and Eu(III) complexes the value of spin-orbit coupling parameter (λ) was calculated. It was stated that the obtained complexes are paramagnetic, except La(III) and Lu(III), which are diamagnetic. Furthermore, the magnetic properties of Sm(III) and Eu(III) compounds significantly differ from the Curie and the Curie–Weiss laws. The metal–ligand bonding in the investigated rare earth element complexes are most probably electrostatic with small participation of covalent bond.