The strategy of "complex as ligand" allowed us to synthesize three new l-oxalato-bridged heterotrinuclear complexes identified as [Cu2Cr(ox)3(Mephen)2]ClO4 (1), [Cu2Fe(ox)3(Mephen)2]ClO4 (2) and [Cu2Fe(ox)3(Me2bpy)2]ClO4 (3), where ox represents the oxalato dianions; Mephen and Me2bpy stand for 5-methyl-1,10-phenanthroline and 4,40-dimethyl-2,20-bipyridine, respectively. The three heterotrinuclear complexes have not yet been isolated in crystalline form suitable for X-ray structure analysis, but based on elemental analyses, molar conductivity and magnetic moment (at room temperature) measurements, IR, ESR and electronic spectra studies, it is proposed that these complexes have an oxalato-bridged structure consisting of two copper(Ⅱ) ions and a chromium(Ⅲ) or an iron (Ⅲ)ion, in which the chromium(Ⅲ) or iron(Ⅲ) ion has an octahedral environment, and the two copper(Ⅱ) ions have a square-planar environment. Variable-temperature magnetic susceptibility (4.2-300K) measurements of the complexes 1 and 2 revealed the occurrence of an intramolecular ferromagnetic interaction between the copper(Ⅱ) and chromium(Ⅲ) ions for 1. On the other hand, the spin-coupling between the copper(Ⅱ) and iron(Ⅲ) ions through the oxalato-bridge in complex 2 is an antiferromagnetic. The magnetic data have been also used to deduce the indicated heterotrinuclear structure. On the basis of the spin-Hamiltonian, H=-2J(SCu1•SM+SCu2•SM) (M=Cr3+ or Fe3+), the magnetic analysis was carried out for the two complexes and the spin-coupling (J) was evaluated as +14.9cm-1 for 1 and )12.7cm-1 for 2.

Twelve new copper(Ⅱ)-lanthanide(Ⅲ) heterobinuclear complexes bridged by N,N¢-oxamidobis(3,5-dibromobenzoato)cuprate(1) [Cu(Br4obbz)]2- and end-capped with 4,4’-dimethyl-2,2’-bipyridine (Me2bpy), namely, Cu(Br4obbz)Ln(Me2bpy)2NO3 (Ln) Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb), have been synthesized and characterized by elemental analyses, molar conductivity measurements, and spectroscopic (IR, UV, ESR) studies. The temperature dependence of the magnetic susceptibility of the Cu(Br4obbz)Gd(Me2bpy)2NO3 complex was further measured over the range 4.2-300 K. The least-squares fit of the experimental susceptibilities based on the spin Hamiltonian operator, H=-2JS1•S2, yielded J=+2.75cm-1. This result indicates the presence of a weak ferromagnetic spin-exchange interaction between Gd(Ⅲ) and Cu(Ⅱ) ions. A plausible mechanism for the ferromagnetic coupling between Gd(Ⅲ) and Cu(Ⅱ) is discussed in terms of spin polarization.

Two new μ-oxamido-bridged heterobinuclear complexes have been synthesized and identified as [Cu(dmoxpn)Mn(Me2phen)2](ClO4)2 (1) and [Cu(dmoxae)Mn(Me2phen)2](ClO4)2 (2), where Me2phen denotes 2,9-dimethyl-1,10-phenanthroline; dmoxpn and dmoxae represent N,N -bis[3-(dimethylamino)-propyl]oxamido and N,N’-bis[2-(dimethylamino)ethyl]oxamido dianions, respectively. Based on elemental analyses, conductivity measurements, IR and electronic spectra studies, it is proposed that the two complexes have oxamido-bridged structures consisting of a copper(Ⅱ) and a manganese(Ⅱ) ions, which have a square-planar environment and a distorted octahedral environment, respectively. The electronic reflectance spectra indicate the presence of exchange-coupling interaction between bridging copper(Ⅱ) and manganese(Ⅱ) ions. Variable-temperature magnetic susceptibility (4.2-300 K) measurements of (1) and (2) complexes revealed the occurrence of an intramolecular antiferromagnetic interaction between the adjacent manganese(Ⅱ) and copper(Ⅱ) ions through the oxamido bridge within each molecule. On the basis of spin Hamiltonian, H=-2JS1S2 the magnetic analysis was carried out for the two complexes and the spin coupling constant (J) was evaluated as -26.9cm-1 for (1) and -38.2cm-1 for (2). The influence of the chelate ring arrangement around the copper(Ⅱ) in the copper(Ⅱ)-manganese(Ⅱ) heterobinuclear complexes on magnetic interactions between the metal ions of this kind of complexes is also discussed.

Two new m-oxalato-bridged CuⅡ2MⅢ-type (M=Cr and Fe) heterotrinuclear complexes have been prepared and identified as [Cu2Cr(ox)3(tmen)2]ClO4 (1) and [Cu2Fe(ox)3(tmen)2]ClO4 (2), where oxrepresents the oxalato dianions; tmen stands for N,N,N0,N0-tetramethylethylenediamine. The two complexes have not yet been isolated in crystalline form suitable for X-ray structure analysis, but based on elemental analyses, molar conductivity and magnetic moment (at room-temperature) measurements, IR, ESR and electronic spectra studies, it is proposed that these complexes have oxalato-bridged structure consisting of two copper(Ⅱ) ions and a chromium(Ⅲ) or an iron(Ⅲ) ion, in which the chromium(Ⅲ) or iron(Ⅲ) ion has an octahedral environment, and the two copper(Ⅱ) ions have a square-planar environment. The two heterotrinuclear complexes were further characterized by variable temperature magnetic susceptibility (4.2-300K) measurements and the magnetic data have been also used to deduce the indicated heterotrinuclear structure. The results derived from least-squares fit of the experimental data have confirmed that the adjacent copper(Ⅱ) and chromium(Ⅲ) ions through the oxalato-bridge in complex (1) are ferromagnetically coupled with the exchange integral J(Cu-Cr)=+10.2 cm-1, while an intramolecular antiferromagnetic coupling is detected between the copper(Ⅱ) and iron(Ⅲ) ions through the oxalato-bridge in complex (2) with the exchange integral J(Cu-Fe)=-11.6 cm-1, on the basis of the spin Hamiltonian operator, H =2J(SCu•SM+SCu2•SM) (M=Cr3+ or Fe3+).