Novel lanthanide complexes with quinoline-2-carboxylic acid: Structural variety and magnetism

By means of the reaction of lanthanide chlorides with quinaldic (quinoline-2-carboxylic, HQA) acid in an aqueous-ethanolic medium in the presence of pyridine, the following complexes were obtained: the known binuclear [Nd2(QA)6(H2O)6]·3H2O (1) one and the novel compounds built of binuclear dicationic and mononuclear anionic moieties [Ln2(QA)4(H2O)4]2+[Ln(QA)4(H2O)]ˉ2·2EtOH·6H2O (Ln = Gd (2), Dy (3), Er (4), Yb (5)), as well as the anionic mononuclear one, [Hpy2]+[Er(QA)4]ˉ·4H2O (6). The complexes 2–5 were characterized by dc and ac magnetic measurements. Complex 3 exhibits the properties of a single-molecule magnet (SMM) in a zero static field with remagnetization barrier (Δeff/kB) of 82 K, while the other complexes display the properties of field-induced SMMs with the Δeff/kB values of 24, 19, and 33 K for the complexes 2, 4, and 5, respectively.