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) angstrom, b = 13-397(3) angstrom, c = 13.966(4) angstrom, 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 angstrom, whereas the two Cu atoms are separated by 6.08 angstrom. 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) angstrom, b = 13,688(7) angstrom, c = 18.728(10) angstrom, 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) angstrom, b = 13.989(4) angstrom, c = 16.774(5) angstrom, 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)center dot 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)center dot S-Gd - J(cuGd)S(Cu2)center dot S-Gd - J(CuCu)S(Cu1)-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.