Copper(II)-Lanthanide(III) Complexes of Symmetric Dinucleating Macrocycle with Two Phenolate Bridges

The first heteronuclear copper(II)-lanthanide(III) complexes, CuLn(fsal-2,2)(NO₃)₃(H₂O)_n (n = 2 for Ln = Nd and n = 1 for Ln = Eu and Gd), of a symmetric macrocyclic dinucleating Schiff base ligand, H₂fsal-2,2, which is a condensation product of two molecules of 2,6-diformyl-4-methylphenol and two molecules of ethylenediamine, were synthesized by the reaction of [N′,N/-bis(3-formyl-5-methylsalicylidene)ethylenediaminato]copper(II) and ethylenediamine in the presence of lanthanide(III) ion as a template, where fsal-2,2 denotes the dianion formed by the deprotonation of two phenolic hydroxyl groups in H₂fsal-2,2. The absorption spectra suggested that substrates possessing N- and O-donor groups, such as amino alcohols, are specifically bound at the Cu-Ln center through nitrogen-coordination to the copper site and through oxygen-coordination to the lanthanide site. The fluorescence intensity of Eu(III) decreased drastically upon forming the Cu-Eu complex. A cryomagnetic susceptibility measurement indicated a ferromagnetic spin-spin interaction between Cu(II) and Gd(III) ions.