Synthesis, crystal structure, and magnetic properties of the first nonanuclear lanthanide(III)-copper(II) complexes of macrocyclic oxamide [NaLn₂Cu₆] (macrocyclic oxamide = 1,4,8,11-tetraazacyclotradecanne-2,3-dione, Ln = Pr, Nd)

Two new nonanuclear lanthanide(Ill)-copper(II) complexes of macrocyclic oxamide [NaPr₂(CuL)₆(H₂0)₆ ](CIO₄)₆Cl·6H₂0 (1) and [NaNd₂(CuL)₆(H₂0)₆] (CIO₄)₆CI·8H₂O (2) have been synthesized and characterized by means of elemental analysis, IR, and electronic spectra, where L = 1,4,8,11-tetraazacyclotradecanne-2,3-dione, The crystal structures of the two complexes have been determined. The structures of 1 and 2 consist of nonanuclear cations, perchlorate and chloride anions, and water molecules. In the two complexes, each copper(II) ion is connected to lanthanide(III) ion via the exo-cis oxygen atoms of the oxamido macrocyclic ligands, resulting in a tetranuclear subunit. The sodium ion links two tetranuclear subunits via the exo oxygen atoms of the oxamido macrocyclic ligands which results in a novel nonanuclear complex. The magnetic properties of the two complexes have been investigated. Preliminary treatment of the magnetic data by considering Ln(III) as free ion cannot give reasonable results, and accurate models involving both the orbital contribution and ligand field effect have to be developed.