Syntheses, Crystal Structures, and Magnetic Properties of [LnIII2(Succinate)3(H2O)2]•0.5H2O [Ln = Pr, Nd, Sm, Eu, Gd, and Dy] Polymeric Networks: Unusual Ferromagnetic Coupling in Gd Derivative

Lanthanide-organic coordination polymeric networks of [LnIII2(suc)3(H2O)2]·0.5H2O [suc = succinate dianion, Ln = Pr (1), Nd (2), Sm (3), Eu (4), Gd (5), and Dy (6)] have been synthesized and characterized by single-crystal X-ray diffraction analyses. The structural determination reveals that complexes are isomorphous, all crystallizing in monoclinic system, space group I2/a. The complexes possess a 3D architecture with Ln ion in a nine-coordination geometry attained by eight oxygen atoms from succinate and one oxygen atom from an aqua ligand. Low-temperature magnetic study indicates that ferromagnetic interaction is present in case of Gd(III) and Dy(III). Antiferromagnetic interaction is observed for the rest of the complexes. Density functional theory calculations are performed which support the existence of a superexchange ferromagnetic coupling in Gd(III) ions, whereas classical crystal field model has been applied to study the complexes 1, 2, 3, and 6.