A new series of heterometallic trinuclear Cu₂Ln complexes [lanthanide ions Ln = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5)] has been synthesized using a Cu(II)-metalloligand derived from a N₂O₂ donor unsymmetrical Schiff base, H₂L (where H₂L = N-α-methylsalicylidene-N′-salicylidene-1,3-propanediamine), and structurally characterized. Among these complexes, [(CuL)₂Gd(NO₃)₃(CH₃CN)₂] (1), [(CuL)₂Tb(NO₃)₃(CH₃CN)₂] (2) and [(CuL)₂Dy(NO₃)₃(CH₃CN)₂] (3) are isomorphic and isostructural. In these complexes two metalloligands coordinate to the central Ln(III) (Ln = Gd, Tb and Dy respectively) ion in a transoid fashion via μ₂-phenoxido oxygen atoms. The Ln(III) ions are deca-coordinated with a distorted tetradecahedron geometry. The two terminal Cu(II) ions of the complexes possess a hexa-coordinated distorted octahedral geometry. In contrast, in complexes [(CuL)₂Ho(NO₃)₃(CH₃CN)], (4) and [(CuL)₂Er(NO₃)₃(CH₃CN)]·0.5(CH₃CN) (5), the two metalloligands coordinated to the Ln(III) ions in a cisoid fashion. The Ho(III) ion in 4 is nona-coordinated with a distorted tricapped trigonal prismatic geometry and the Er(III) ion in 5 is octa-coordinated with a distorted square antiprismatic geometry. The two terminal Cu(II) ions in complexes 4 and 5 are penta-coordinated with a distorted square-pyramidal geometry. The dc magnetic susceptibilities and field dependent magnetization measurement of complex 1 reveal the occurrence of ferromagnetic interactions between Cu(II) and Gd(III) ions as well as intermolecular antiferromagnetic interactions. Both complexes 2 and 3 show ferromagnetic interactions between Cu(II) and Ln(III) ions. The ac magnetic susceptibilities of all the complexes were also recorded and it was found that only complexes 2 and 3 exhibit slow relaxation of magnetization reorientation below 10 K at 2000 Oe applied dc field, this being characteristic of single molecule magnets.

中文翻译：

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一系列镧系离子与Salen型不对称席夫碱（H ₂ L）的（CuL）₂ Ln络合物的结构变化：Dy和Tb衍生物作为潜在的单分子磁体

使用Cu（II）-合成了一系列新的杂金属三核Cu ₂ Ln配合物[镧系元素离子Ln = Gd（1），Tb（2），Dy（3），Ho（4）和Er（5）] 。衍生自N ₂ O ₂供体非对称席夫碱H ₂ L（其中H ₂ L = N - α-甲基水杨基-N'-水杨基-1，3-丙二胺）的金属配体，并在结构上进行表征。在这些络合物中，[（CuL）₂ Gd（NO ₃）₃（CH ₃ CN）₂]（1），[（CuL）₂ Tb（NO ₃）₃（CH ₃ CN）₂ ]（2）和[（CuL）₂ Dy（NO ₃）₃（CH ₃ CN）₂ ]（3）是同构的和同构。在这些配合物2个metalloligands坐标到Ln的中央（III）（Ln为钆，铽和Dy分别）离子在transoid方式经由μ _2个-phenoxido氧原子。Ln（III）离子以扭曲的十四面体几何形状进行十配位。二端子Cu（II）的离子具有六配位扭曲的八面体几何形状。相反，在络合物中[（CuL）₂ Ho（NO ₃）₃（CH ₃ CN）]，（4）和[（CuL）₂ Er（NO ₃）₃（CH ₃ CN）]·0.5（CH ₃ CN ）（5），两个金属配体以cisoid方式与Ln（III）离子配位。何（III中）离子4是壬协调与扭曲三冠三角棱柱几何形状和铒（III）的离子5八角形与扭曲的方形反棱镜几何体协调。配合物4和5中的两个末端Cu（II）离子以扭曲的方锥几何结构进行五配位。配合物1的dc磁化率和与场有关的磁化强度测量表明，Cu（II）和Gd（III）离子之间发生铁磁相互作用以及分子间反铁磁相互作用。配合物2和3均显示Cu（II）和Ln（III）之间的铁磁相互作用）离子。还记录了所有配合物的交流磁化率，发现只有配合物2和3在2000 Oe施加的dc磁场下在10 K以下显示出磁化取向的缓慢弛豫，这是单分子磁体的特征。