Synthesis, Crystal Structure, and Magnetic Property of New Trispin Ln(III)-Nitronyl Nitroxide Complexes

Four Ln(III) complexes based on a new nitronyl nitroxide radical have been synthesized and structurally characterized: {Ln(hfac)(3)[NITPh(MeO)(2)](2)} (Ln=Eu(1), Gd(2), Tb(3), Dy(4); NITPh(MeO)(2)=2-(3,4-dimethoxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac=hexafluoroacetylacetonate). The single-crystal X-ray diffraction analysis shows that these complexes have similar mononuclear trispin structures, in which central Ln(III) ion is eight-coordinated by two O-atoms from two nitroxide groups and six O-atoms from three hfac anions. The variable temperature magnetic susceptibility study reveals that there exist ferromagnetic interactions between Gd(III) and the radicals, and antiferromagnetic interactions between two radicals (J(Gd-Rad)=3.40cm(-1), J(Rad-Rad)=-9.99cm(-1)) in complex 2. Meanwhile, antiferromagnetic interactions are estimated between Eu(III) (or Dy(III)) and radicals in complexes 1 and 4, and ferromagnetic interaction between Tb(III) and radicals in complex 3, respectively.