Structure And Magnetic Study Of Multi-spin Metal-Nitronyl Nitroxide Radical Complex Incooperating Organic Ligand With Polyfluorine Substituents

Three nitronyl nitroxide radicals have been synthesized,of which a new nitroxide radical NITPh-3-OCH₂Ph（2-（3-benzyloxyphenyl）-4,4,5,5-tetra–methyl-imidazoline-1-oxyl-3–oxide）has been characterized by IR,elemental analyses,ESR and X-ray crystallographic method.With tetrafluoroterephthalate（tftpa）as bridging coligand,five transition metal complexes have been synthesized using pyridyl substituted nitronyl nitroxide radicals:[Co（NIT4Py）₂（tftpa）（CH₃OH）（H₂O）]（1）,[Ni（NIT4Py）₂（tftpa）（CH₃OH）（H₂O）]（2）,[Zn（NIT4-Py）₂（tftpa）（CH₃OH）（H₂O）]（3）,[Cu（NIT4Py）₂（tftpa）（H₂O）]（4）and[Cu（NIT3Py）₂（tftpa）]（5）.Five mononuclear lanthanide complexes[Ln（hfac）₃（NITPh-3-OCH₂Ph）₂]（Ln=Sm（6）,Eu（7）,Gd（8）,Tb（9）,Dy（10））have been prepared with Ln（hfac）₃·2H₂O（hfac=hexafluoroacethlacetonate）and NITPh-3-OCH₂Ph radical.These complexes were characterized by IR,X-ray crystallographic methods.The magnetic properties of ten complexes have been studied.All of complexes 1-5 exhibit one-dimensional chain structures,with tetrafluoro-terephthalate as double monodentate bridging ligand.In complexes 1-4,two-dimensional network structures are formed based on the interchain hydrogen bonds.For complex 1,there exist weak antiferromagnetic interactions between Co（II）and the NIT4Py radicals.For complex 2,there exist weak antiferromagnetic interactions between Ni（II）and the NIT4Py radicals.For complex 4,there exist weak antiferromagnetic interactions between Cu（II）and two NIT4Py radical ligands.For complex 5,there coexist ferromagnetic and antiferromagnetic interactions between Cu（II）and two NIT3Py radicals,respectively.Complexes 6-10 possess mononuclear structures,in which the Ln（III）ions are eight-coordinated with six oxygen atoms of three bidentate hfac anions and two oxygen atoms of two NITPh-3-OCH₂Ph radical ligands.For complexes 7,9 and 10,antiferromagnetic coupling interactions are estimated between Ln（III）and radical ligands.For complex 8,two types of weak antiferromagnetic interactions have been found both between Gd（III）and radicals,or between two radical ligands.The AC susceptibility of complex 9 shows obvious frequency-dependent out-of-phase signals,implying the slow relaxation of the magnetization as single-molecule magnet（SMM）.