Synthesis and Magnetic Property of Copper(II)–Lanthanide(III) Complexes [{CuIILLnIII(<i>o</i>-van)(CH3COO)(MeOH)}2]·2H2O (LnIII = GdIII, TbIII, and DyIII; H3L = 1-(2-Hydroxybenzamido)-2-(2-hydroxy-3-methoxybenzylideneamino)ethane; <i>o</i>-van = 3-Methoxysalicylaldehydato)

<jats:title>Abstract</jats:title> <jats:p>Three tetranuclear copper(II)–lanthanide(III) complexes, [{CuIILLnIII(o-van)(CH3COO)(MeOH)}2]·2H2O (LnIII = GdIII, TbIII, and DyIII), were synthesized and characterized, where H3L is 1-(2-hydroxybenzamido)-2-(2-hydroxy-3-methoxybenzylideneamino)ethane and o-van is 3-methoxysalicylaldehydato. These compounds are isomorphous to each other and consist of a cyclic tetranuclear CuII2LnIII2 structure, in which the CuII and LnIII ions are alternately arrayed and the CuII component complex. [CuIIL]− unit functions as a “bridging ligand-complex” between two adjacent LnIII ions through the phenolato and methoxy oxygen atoms at one side and the amido oxygen atom at the another side. The temperature-dependent magnetic susceptibilities from 2.0 to 300.0 K and the field-dependent magnetizations at 2.0 K from 0 to 5 T showed that the magnetic interaction between CuII and each of the lanthanide ions is ferromagnetic. The magnetic susceptibilities of [{CuIILGdIII(o-van)(CH3COO)(MeOH)}2]·2H2O were analyzed by using a spin-only Hamiltonian H = −2J1(SCu1SGd1 + SCu2SGd2) − 2J2(SCu1SGd2 + SCu2SGd1) based on a cyclic tetranuclear structure and gave the best-fit parameters of g = 1.97, J1 = +3.8 cm−1, J2 = +0.7 cm−1, and zJ′ = −0.01 cm−1. The magnetization data at 2.0 K of [{CuIILGdIII(o-van)(CH3COO)(MeOH)}2]·2H2O were well reproduced by using a Brillouin function with an S = 8 spin ground state due to the ferromagnetic interactions between CuII and GdIII ions and g = 1.97. The ac magnetic susceptibilities of [{CuIILLnIII(o-van)(CH3COO)(MeOH)}2]·2H2O (LnIII = TbIII and DyIII) in the temperature range 1.8–10.0 K with a 3 G ac field oscillating in the range 1–1000 Hz showed a frequency dependence characteristic of SMMs.</jats:p>