Synthesis and Magnetism of Copper(II)-Ln(III)-Copper(II) (Ln = La, Nd, Eu, Gd, Tb, Dy, Ho, Er) Heterotrinuclear Complexes with N,N_-Bis(2-methyl-2-aminopropyl)oxamidocopper(II)

Eight new mi-oxamido-bridged copper(II)-lanthanide(III)-copper(II) heterotrinuclear complexes formulated as Cu2(oxmap)2Ln(NO3)3 (Ln = La, Nd, Eu, Gd, Tb, Dy,Ho, Er), where oxmap stands for N,N'-bis(2-methyl-2-aminopropyl)oxamido dianions, have been synthesized by the strategy of "complex as ligand", and characterized by elemental analyses, molar conductivity measurements, IR and electronic spectral studies. The variable temperature magnetic susceptibility (2~300 K), ESR measurements and studies of the Cu2(oxmap)2Gd(NO3)3 complex have revealed that the central gadolinium(III) and terminal copper(II) ions are ferromagnetically coupled with the exchange integral J(Cu-Gd) = +2.19 cm-1, while an antiferromagnetic coupling is detected between the terminal copper( II) ions with the exchange integral J'(Cu-Cu) = _0.15 cm-1, on the basis of the spin Hamiltonian operator [H = -2J(S Cu1. S Gd + S Cu2. S Gd)-2J'(ScCU1.SCu2)].A plausible mechanism for the ferromagnetic coupling between copper(II) and gadolinium(III) is discussed in terms of spin polarization.