Synthesis, Structure And Magnetic Property Of Multisubstituted Aromatic Nitronyl Nitroxide Radicals And Their Metal Complexes

In this paper, two new nitronyl nitroxide radicals have been synthesized successfully: NITPh-3,4-(OMe)2(2-(3?,4?-dimethoxyphenyl)-4,4,5,5–tetramethyl-imidazoline-1-oxyl-3-oxide) and NITPh-3-OEt-4-OMe(2-(3-ethoxy-4–methoxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide). They were characterized by IR, UV-vis, Elemental analysis, XRD, ESR and single-crystal X-ray diffraction.Reacted with Ln(hfac)3·2H2O [Ln = Sm, Eu, Gd, Tb, Dy;hfac = hexafiuoroacetyl-acetonate) and Mn(hfac)2·2H2O respectively, eleven novel complexes have been obtained: [Ln(hfac)3(NITPh-3,4-(OMe)2)2] [Ln = Sm(1), Eu(2), Gd(3), Tb(4), Dy(5)],[Ln(hfac)3(NIPh-3-OEt-4-OMe)(IMHPh-3-OEt-4-OMe)] [Ln = Sm(6), Eu(7), Gd(8)],[Ln(hfac)3(NIPh-3-OEt-4-OMe)2] [Ln = Tb(9), Dy(10)] and [Mn(hfac)2(IMHPh-3,4-(OMe)2)]2(11).Complexes 1-5 are mononuclear tri-spin structures, in which central Ln(III) ion is eight-coordinated distorted dodecahedron coordinated by two oxygen atoms from two nitroxide groups and six oxygen atoms from three hfac anions. Complexes 6-10 are also mononuclear structures, of which 9 and 10 are similar to complexes 1-5.However, the prominent feature of complexes 6-8 is that a radical NITPh-3-OEt-4-OMe was reduced to IMHPh-3-OEt-4-OMe. The polyhedron around the Ln(III) ion is also an eight-coordinated distorted dodecahedron with triangular faces. In complex 11, two bridging IMHPh-3,4-(OMe)2 ligands connect two Mn(II)ions, forming a dinuclear structure, in which IMHPh-3,4-(OMe)2 is a reduced form of NITPh-3,4-(OMe)2. The central Mn(Ⅱ) ions adopt six-coordinated distorted octahedron, which coordinated two bidentate hfac ligands and two IMHPh-3,4-(OMe)2.The magnetic properties of these complexes have been studied. For 2 and 7, the negative zJ’ value indicates antiferromagnetic interaction between Eu(III) and radical;For 3, the positive J1 value indicates that there is weak ferromagnetic interaction between Gd(III) ion and the NITPh(OMe)2 radicals, and the negative J2 shows the antiferromagnetic interaction between two radicals; For 4 and 9, the positive zJ’values indicate ferromagnetic interactions between Tb(III) and radicals; For complexes 5 and 10, the negative zJ’ values indicate antiferromagnetic interactions between Dy(III) and radicals. The ac magnetic susceptibilities demonstrate that 4, 5, 9and 10 don’t express SMMs behavior.