Syntheses, Characterization, and Properties of Three-Dimensional Pillared Frameworks with Entanglement

Six new coordination polymers, namely, [Cd3(L)2(dpa)2(H2O)] (1), [Co3(L)2(dpa)2(H2O)2]·H2O (2), [Cd(L)(chda)0.5] (3), [Cd(L)(dc)0.5(H2O)] (4), [Cd2(L)2(cca)]·2H2O (5), and [Cd2(L)2(cppa)]·2H2O (6) [HL = 3,5-di(imidazol-1-yl)benzoic acid, H2dpa = diphenic acid, H2chda = 1,4-cyclohexanedicarboxylic acid, H2dc = 1,4-benzenediacrylic acid, H2cca = 4-carboxycinnamic acid, H2cppa = 3-(4-carboxyphenyl)propionic acid] have been obtained under hydrothermal conditions. Complexes 1 and 2 are novel (3,6)-connected three-dimensional (3D) frameworks based on trinuclear subunits. Complex 3 shows a rare 4-fold interpenetrating 3D dmc net, and 4 features a uninodal 6-connected 3D self-penetrating framework. Both 5 and 6 possess unusual 3-fold interpenetrating 3D (3,4)-connected InS nets. In 1−6 each metal atom is coordinated by the combination of L− and auxiliary carboxylate ligands. In 1 and 2 the auxiliary carboxylate ligand plays an important role in the formation of metal cluster based subunits. In 3−6 the auxiliary carboxylate ligands pillar the metal - L− two-dimensional networks to form entangled 3D frameworks. Furthermore, the photoluminescence and thermal stabilities of complexes 1−6 were investigated. The temperature-dependent magnetic susceptibility measurements of compound 2 show the ferromagnetic interactions between the metal centers mediated through the μ-O and/or O−C−O linkages.