Three isostructural one-dimensional lanthanide complexes with formulae of [Dy(H2L)(H2O)2]·Cl·6H2O (1), [Dy0.067Y0.933(H2L)(H2O)2]·Cl·6H2O (1′,) and [Gd(H2L)(H2O)2]·Cl·6H2O (2), where H2L2– is the dianion of the bis-hydrazone (N′,N‴E,N′,N‴E)-N′,N‴-(pyridine-2,6-diylbis(methanylylidene))bis(2-hydroxybenzohydrazide), were synthesized and structurally characterized. Single-molecule magnet (SMM) behavior was observed for the DyIII compound under an applied dc field, which is rarely seen for a nine-coordinate DyIII compound with a hula-hoop coordination geometry. The SMM behavior is ascribed to the single-ion properties of DyIII, which is proved by comparison of the ac magnetic susceptibilities of 1 and the Y/Dy diluted complex 1′. Magnetic studies indicate that the GdIII analogue shows a magnetocaloric effect with a maximum entropy change −ΔSm of 21.32 J kg–1 K–1 at ΔH = 7 T and 3 K.