Two-Dimensional Coordination Polymers Exhibiting Antiferromagnetic Gd(III)−Cu(II) Coupling

A series of carboxylate-bridged 4f−3d complexes Cat+[Cu(nta)Cl]2Ln(H2O)4 (Cat+ = Na+ or K+, Ln3+ = Gd3+ or La3+, and nta3- = nitrilotriacetate) have been synthesized by self-assembly of CuCl2·4H2O, H3nta, and LnCl3·6H2O in the presence of stoichiometric amounts of CatOH. X-ray diffraction analysis revealed that these complexes are isostructural and have a novel layered structure. The Ln3+ ion is coordinated by nine oxygen atoms of four [Cu(nta)Cl]2- and four water molecules, while each [Cu(nta)Cl]2- anion connects two Ln3+ using carboxylate oxygen atoms giving rise to a rhombus-like layered structure. The alkaline metal ions Cat+ are situated between the layers and coordinated to the oxygen atoms of [Cu(nta)Cl]2- generating a quasi-three-dimensional network. Magnetic studies indicate the presence of apparent antiferromagnetic coupling between Cu(II) and Gd(III) in KCu2Gd and NaCu2Gd. The magnetic susceptibilities of KCu2La were simulated by using a quadratic model, which suggests a weak antiferromagnetic Cu(II)−Cu(II) coupling.