Nature of copper(II)-lanthanide(III) magnetic interactions and generation of a large magnetic moment with magnetic anisotropy of 3d-4f cyclic cylindrical tetranuclear complexes [Cu(II)LLn(III)(hfaC)(2)](2), (H3L=1-(2-hydroxybenzamido)-2-(2-hydroxy-3-

摘要

A cyclic cylindrical 3d-4f tetranuclear structure, in which the 3d and 4f magnetic ions are arrayed alternately, has been found to be a suitable molecular design to produce a large magnetic moment and large magnetic anisotropy. Complexes 3-10 with the chemical formula [MLLn(hfac)(2)](2) ((M-II, Ln(III)) = (Cu, Eu) (3), (Cu, Gd) (4), (Cu, Tb) (5), (Cu, Dy) (6), (Ni, Eu) (7), (Ni, Gd) (8), (Ni, Tb) (9), (Ni, Dy) (10)) have been synthesized, where H3L = 1-(2hydroxybenzamido)-2-(2-hydroxy-3-methoxybenzylideneamino)ethane and Hhfac = hexafluoroacetylacetone. The powder X-ray diffractions and FAB-mass spectra demonstrated that these complexes assume a similar tetranuclear structure. The crystal structures of 4 and 5 showed that each complex has a cyclic cylindrical tetranuclear Cu(2)(II)Ln(2)(III) structure, in which the Cull complex functions as a "bridging ligand-complex" to two adjacent Ln(III) ions. The temperature-dependent magnetic susceptibilities from 2 to 300 K and the field-dependent magnetizations at 2 K from 0 to 5 T have been measured for four pairs of Cu(2)(II)Ln(2)(III) and Ni(2)(II)Ln(2)(III), in which compound Ni(2)(II)Ln(2)(II) containing diamagnetic Ni-II ion was used as the reference complex to evaluate the Cu-II-Ln(III) magnetic interaction. Comparison of the magnetic properties of the CU(2)(II)Ln(2)(III) complex with those of the corresponding Ni(2)(II)Ln(2)(III) complex showed that the magnetic interaction between Cu-II and Eu-III ions is weakly ferromagnetic and that between Cu-II and either of Gd-III, Tb-III, and Dy-III ions is ferromagnetic. Complex (Cu2Gd2III)-Gd-II, 4, has an S = 8 spin ground state, due to the ferromagnetic spin coupling between S-Gd = 7/2 and S-Cu = 1/2 with coupling constants of J(1) = +3.1 cm(-1) and J(2) = +1.2 cm(-1). The magnetic measurements showed that compounds 5 and 6, Cu(2)(II)Ln(2)(III) (Ln(III) = Tb, Dy), exhibit large magnetic moments and large magnetic anisotropy due to the Ln(III) ion. [References: 50]