Synthesis and Magnetism of Copper(II)-lanthanide(III)-copper(II) Heterotrinuclear Complexes with N,N′-bis [2-(dimethylamino)ethyl]oxamidocopper(II)

Abstract

Nine new μ-oxamido-bridged copper(II)-lanthanide(III)-copper(II) heterotrinuclear complexes described by the overall formula Cu2(dmoxae)2Ln(NO3)3 {Ln = Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er; dmoxae = N,N′-bis[2-(dimethylamino)ethyl]oxamido dianions} have been synthesized by the strategy of ‘complex as ligand’, and characterized by elemental analyses, molar conductivity measurements, i.r. and electronic spectral studies. The variable-temperature susceptibility (2–300 K), e.s.r. measurements, and studies of the Cu2(dmoxae)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) = +2.1 cm−1, while an antiferromagnetic coupling is detected between the terminal copper(II) ions with J′(Cu-Cu)=−0.36 cm−1, on the basis of the spin Hamiltonian operator \([\hat {H}=-2{J}(\hat {S}_{\rm Cu1} \cdot \hat{S}_{\rm Gd} +\hat {S}_{\rm Cu2} \cdot \hat {S}_{\rm Gd})-2{J}^{\prime} (\hat{S}_{\rm Cu1} \cdot \hat {S}_{\rm Cu2})]\). A plausible mechanism for the ferromagnetic coupling between copper(II) and gadolinium(III) is discussed in terms of spin polarization.