Structure And Properties Of Co(Ⅱ), Mn(Ⅱ)-Nitroxide Radicals Multi-species Complexes

The design and synthesis of transition metal complexes with radical is one of themost attractive fields in the molecular-based magnetic materials. In order toinvestigate the correlation between the structure and magnetic properties, four nitronylnitroxide radicals and seven novel complexes have been synthesized. The structuresof seven complexes have been determined through X-ray diffraction single-crystaltechnique. Their TG-DTG thermal properties and magnetic properties were studied.The four synthesized radical ligands are2-（4’-methylthiophenyl）-4,4,5,5–tetramethylimidazoline-1-oxyl-3-oxide（NITPhSMe）,2-（4’-tert-butylphenyl）-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide （NITPht-Bu）,（2-（4’-sec-propylphenyl）-4,4,5,5–tetramethylimidazoline-1-oxyl-3-oxide）（NITPhi-Pr）,2-（4’-n-butyloxyphenyl）-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide （NITPhOn-Bu）, respectively. Thecomplexes can be classified mononuclear complex [Co（hfac）2（NITPhSMe）2（1）,Mn（hfac）2（NITPhSMe）2（2） and Co（hfac）₂（NITPhi-Pr）₂（3）], dimer complex[[Mn₂（hfac）4（NITPhi-Pr）2]·2C₇H₁₆（4）,[Mn₂（hfac）4（NITPht-Bu）2]·2C7H16（5） andCo₂（hfac）_4L2（6）] and one-dimensional complex [[Mn（hfac）2NITPhOn-Bu]n（7）]. TheMn（II） and Co（II） ions in the complexes are six-coordinated with four oxygen atomsof two chelating hfac anions and two oxygen atoms from two radicals NITR.Complex Co（hfac）₂（NITPhSMe）₂（1） shows strong antiferromagnetic interactionbetween Co（II） and NITPhSMe. Complex Mn（hfac）2（NITPhSMe）₂（2） exhibits strongmagnetic moment in low temperature range, which suggests long-range order in thisrange. The related magnetic measurements are being tested. These complexes begin todecompose at about130℃, and give the corresponding stable metal oxide Mn3O4,Co₃O₄or Co₂O₃as end products nearly750℃.Many coordination compounds made of transition metal and nitronyl nitroxideradicals have been studied. In addition, we also process thermodynamic analysis forthe complexes, and derived the thermal decomposition which provide a scientificexperiment basis for these new functional complexes magnetic materials...