Synthesis, structures, and magnetic properties of tri- and dinuclear copper(II)-gadolinium(III) complexes of linear oligooxime ligands

We have designed and synthesized a new Cu2Gd heterotrinuclear complex, LCu2Gd(OAc)3] (1), where H4L is a bis(salen)-type tetraoxime ligand useful in the synthesis of discrete (3d)2(4f) complexes. Complex 1 crystallizes in the triclinic system, space group P1, with unit cell parameters a = 12.442(4) A, b = 13.397(3) A, c = 13.966(4) A, alpha = 77.052(8) degrees, beta = 88.656(10) degrees, gamma = 77.761(8) degrees, and Z = 2. In the crystal structure of 1, Cu-Gd distances are 3.3-3.5 A, whereas the two Cu atoms are separated by 6.08 A. The corresponding dinuclear CuGd complexes, 2 and 3, with mono(salen)-type chelate 3-MeOsalamo were also synthesized. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with unit cell parameters a = 13.869(8) A, b = 13.688(7) A, c = 18.728(10) A, beta = 92.861(8) degrees, and Z = 4, and complex 3 crystallizes in the triclinic system, space group P1, with unit cell parameters a = 12.319(4) A, b = 13.989(4) A, c = 16.774(5) A, alpha = 64.699(14) degrees, beta = 66.672(13) degrees, gamma = 76.891(17) degrees, and Z = 4. Interaction between Cu(II) and Gd(III) in the dinuclear complexes 2 and 3 is ferromagnetic (J = 4.5 and 7.6 cm(-1), respectively, using spin Hamiltonian H = -JS(Cu) x S(Gd)) as observed in the previously prepared LCuGdX3] complexes, where L is a salen-type chelate. Magnetic data for the Cu2Gd trinuclear complex can be reasonably interpreted with the use of a spin Hamiltonian H = -J(CuGd)S(Cu1) x S(Gd) - J(CuGd)S(Cu2) x S(Gd) - J(CuCu)S(Cu1) x S(Cu2) with J(CuGd) = 5.0 cm(-1) and J(CuCu) = 0 cm(-1). The S = 9/2 ground state resulted from the ferromagnetic interaction among the Cu(II)-Gd(III)-Cu(II) triad was also supported by the saturation magnetization at 1.8 K.