| In this paper, four nitronyl nitroxide radicals have been synthesized successfully, including three benzyloxyphenyl substituted nitronyl nitroxide radicals: NITPh-2- OCH2Ph(2-(2-benzyloxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), NITPh-3-OCH2Ph(2-(3-benzyloxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), NITPh-4-OCH2Ph(2-(4-benzyloxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1- oxyl-3-oxide) and one bihalogenated phenyl substituted nitronyl nitroxide radical NITPh Br F(2-(2-fluoro-4-bromophenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3- oxide). They were characterized by IR, UV-vis, ESR and single-crystal X-ray diffraction. The four radicals reacted with Ln(hfac)3·2H2O and Mn(hfac)2·2H2O(hfac = hexafiuoroacetylacetonate) respectively and yielded twelve novel complexes: {[Ln(hfac)3(NITPh Br F)2]·0.5C7H16}[Ln = Sm(1), Eu(2), Gd(3), Tb(4), Dy(5)], [Ln(hfac)3(NITPh-2-OCH2Ph)(IMHPh-2-OCH2Ph)][Ln=Sm(6), Eu(7), Tb(9), Dy(10)], [ Gd(hfac)3(NITPh-2-OCH2Ph)2](8), [Mn(hfac)2(IMHPh-3-OCH2Ph)]2·0.5C7H16(11), [Mn(hfac)2(NITPh-4-OCH2Ph)]2(12).Complexes 1-5 are composed of mononuclear molecule [Ln(hfac)3(NITPh Br F)2] and solvent molecule C7H16. In these complexes, the Ln(III) ion is coordinated with three bidentate hfac anions and two monodentate NITPh Br F radicals. The polyhedron around the Ln(Ⅲ) ion is a eight-coordinated distorted dodecahedron. Complexes 6-10 are mononuclear. The structure of [Gd(hfac)3(NITPh-2-OCH2Ph)2](8) is similar to complexes 1-5. However, the characteristics of the other complexes is that a radical NITPh-2-OCH2 Ph was reduced to IMHPh-2-OCH2 Ph. The polyhedron around the Ln(Ⅲ) ion is also a eight-coordinated distorted dodecahedron. Compound [Mn(hfac)2(IMHPh-3-OCH2Ph)]2·0.5C7H16(11) was a dinuclear complex and both of the radicals are reduced to IMHPh-3-OCH2 Ph. Two center metal Mn(Ⅱ) ions are bridged by two IMHPh-3-OCH2 Ph ligands, forming a dinuclear structure. The Mn(Ⅱ) ion is a six-coordinated distorted octahedron. In complex 12, the NITPh-4-OCH2 Ph radical and Mn(hfac)2 moieties are arranged alternately, forming one-dimensional chain. Each Mn(Ⅱ) ion is also a six-coordinated distorted octahedron.The molar heat capacities of 1-12 were measured by DSC below the decomposition temperature. The average values of the molar heat capacities are fitted to the polynomial equations using the least-squares method. Furthermore, the smoothed molar heat capacities and thermodynamic functions(HT-H298.15K),(ST-S298.15K) and(GT-G298.15K) are calculated based on the relevant polynomial equations of the complexes. No obvious endothermic and exothermic peak are observed in the Cp,m ~ T curves, implying no phase change occurs in the measured temperature range.The variable temperature magnetic susceptibility of complexes 1-5 were measured. For complex 2, the negative z J’ value(-3.48cm-1) indicates a weak antiferromagnetic interaction between spin carriers. For complex 3, the positive J1 value(2.14 cm-1)indicates weak ferromagnetic coupling interactions between Gd(III) and radicals, and the negative J2 value(-3.72 cm-1)indicates a intramolecular weak antiferromagnetic coupling interaction between two radicals. Weak antiferromagnetic interactions are found between Tb(III)(or Dy(III)) and radicals in complexes 4 and 5(-0.03cm-1 and-0.068 cm-1, respectively). The ac magnetic susceptibility suggests that complexes 4 and 5 are not SMMs. The variable temperature magnetic susceptibility of complexes 6-10 were measured. It is difficult to fit this series of measured data, which be related to the reduced derivative of unstable radical. The ac magnetic susceptibility suggested that complexes 9 and 10 might not be SMMs as well. Magnetic property of complex [Mn(hfac)2(NITPh-4-OCH2Ph)](12) was studied. The result exhibits the characteristics of typical ferrimagnetic one-dimensional chain with J =-483 cm-1 between Mn(II) and the radical, and the purity factor is 99.9%. |
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