Synthesis, Structure And Magnetic Property Of Di-substituted Phenyl Nitronyl Nitroxide- Metal Complexes

In this paper, two nitronyl nitroxide radicals, NITPh-2,4-(OCH3)2(2-(2’,4’-dimethoxypheny)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and NITPh-2-F-5-Br(2-(5-bromo-2-fluorophenyl)-tetramethylimidazoline-1-oxyl-3- oxide) have been synthesized successfully. They were characterized by IR, UV-vis, XRD and ESR.Eleven novel complexes, Ln(hfac)3(NITPh-2,4-(OCH3)2)(IMHPh-2,4-(OCH3)2) [Ln =Eu(1), Tb(3)], Ln(hfac)3(NITPh-2,4-(OCH3)2)2 [Ln = Gd(2), Dy(4)], Ln(hfac)3(NITPh-2-F-5-Br)2·0.5CH2Cl2(Ln = Sm(5), Gd(6), Tb(7)), Dy(hfac)3(NITPh-2-F-5-Br)2(8), Mn2(hfac)4(IMHPh-2,4-(OCH3)2)2(9), Ni(hfac)2(NITPh-2,4-(OCH3)2)-(H2O)(10) and [Mn2(hfac)4(IMHPh-2-F-5-Br)2](NITPh-2-F-5-Br)(11) have been prepared with two new radical ligands, reacted with Ln(hfac)3·2H2O or M(hfac)2·2H2O(hfac = hexafluoroacetylacetonate, M = Mn, Ni).The X-ray revealed that complexes(1)-(8) possess mononuclear structure, in which the central Ln(Ⅲ) is octacoordinated by six oxygen atoms from three bidentate hfac ligands and two oxygen atoms from two nitronyl nitroxide ligands. The geometry around Ln(III) ion is a distorted dodecahedron. The NITR nitronyl nitroxide radical is partly converted into the reduced derivatives IMHR in complexes(2),(4),(9) and(11).Complexes(9) and(11) include dimeric units [Mn(hfac)2(IMHR)], and the Mn(Ⅱ) is hexacoordinated to two hfac anions and to two oxygen atoms of two bridging IMHR radicals. Complex(10) possess mononuclear structure, in which Ni(Ⅱ) is hexacoordinated to two hfac anions, a oxygen atoms of NITR radical and a oxygen atom of coordinated water molecule. Quasi-dinuclear molecule is formed with the intermolecular hydrogen bonds in(10).The magnetic properties were studied for these complexes. For(1), negative z J’value reflects the antiferromagnetic interaction between Eu(III) ion and radicals. For(2) and(6), the positive J1 values indicate weak ferromagnetic interactions between Gd(III) and radicals, while reflect antiferromagnetic interaction between radicals with negative J2. The positive z J’ value indicates the weak ferromagnetic interaction in(3),while the negative z J’ value reflects the antiferromagnetic interaction between Tb(III)ion and radicals in(7). For(4) and(8), the negative z J’ values reflect antiferromagnetic interactions between Dy(III) and radicals. The alternating-current susceptibilities of(3),(4),(7) and(8) show that they don’t express SMM behavior.Antiferromagnetic interactions between two Mn(II) ions are found in(9) and(11).