title: Systematic studies of the structures and magnetic properties for a family of cubane complexes with the formula: [M2Ln2] (Ln = Dy, Gd; M = Ni, Zn) and [Ni2Y2].
abstract: Studies of magnetic properties of a family of tetranuclear M(II)(2)Ln(III)(2) (M = Ni, Zn; Ln = Dy, Gd and Y) complexes with hmp (anion of 2-hydroxymethylpyridine) and benzoate as ligands are reported. In these complexes, metal ions (M or Ln) occupy the four alternative corners of a distorted cubane with oxygen atoms from alkoxyl groups on the others. Complexes 1, 2 and 3 crystallized in P2(1)/c and complexes 4 and 5 in C2/c space groups. Although in different space groups, complexes 1-5 have very similar structures which permit the magnetic interactions to be systematically compared with respect to metal ion pairs. In complex 3 (Ni(2)Y(2)), clear ferromagnetic coupling between Ni(II) ions can be seen, with: g = 2.16, S = 2, D = -0.95 cm(-1), J = +3.77 cm(-1) (or g = 2.20, S = 2, D = +1.51 cm(-1)). In complex 5 (Zn(2)Gd(2)), a very weak antiferromagnetic coupling between the Gd(III) ions was observed: g = 2.08, J = -0.05 cm(-1). Based on these data, we concluded that the decrease in χ(M)T-T upon cooling for complex 2 (Zn(2)Dy(2)) might be partly due to antiferromagnetic coupling between Dy(III) ions. The data from complex 4 (Ni(2)Gd(2)) were analyzed based on the preceding results and gave moderate ferromagnetic coupling between Ni(II) and Gd(III) with J = 0.26 cm(-1). A detailed study of magnetic properties of complex 1 (Ni(2)Dy(2)) was not possible, because of its strong orbital contributions from Dy(III) ions. In addition, frequency-dependent out-of-phase signals were clearly observed for both complexes 1 and 2 which can be attributed to magnetoanisotropy contributions from Dy(III) ions.
authors: Department of Chemistry, Fu Jen Catholic University, Hsinchuang, Taipei, 24205, Taiwan, Republic of China.
authors: Wan-Rong
authors: WR
authors: Yu
authors: Gene-Hsian
authors: GH
authors: Lee
authors: En-Che
authors: EC
authors: Yang