Mononuclear lanthanide complexes with 18-crown-6 ether: synthesis, characterization, magnetic properties, and theoretical studies

Abstract

A family of lanthanide metal complexes with general formula [Ln(H2O)3(18-crown-6)](ClO4)3 (Ln: TbIII, DyIII, ErIII and YbIII) has been synthesized. Their magnetic properties have been characterized by DC and AC SQUID measurements and analyzed with the help of CASSCF-type calculations. The DyIII and YbIII compounds show slow relaxation of the magnetization under an external magnetic field. The analysis of the dependence of the relaxation time with the temperature and external magnetic field reveals that the main contributions are respectively the quantum tunneling and the Raman term, respectively. The analysis of the beta electron density and electrostatic potentials indicate that the axial ligands (three water molecules) generate a relatively small repulsion with the lanthanide electron density being the reason of the moderate magnetic anisotropy found in these systems.