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

Six new coordination polymers, namely, [Cd-3(L)(2)(dPa)(2)(H2O)] (1), [Co-3(L)(2)(dpa)(2)(H2O)(2)] center dot H2O (2), [Cd(L)(chda)(0.5)] (3), [Cd(L)(dc)(0.5)-(H2O)] (4), [Cd-2(L)(2)(cca)] center dot 2H(2)O (5), and [Cd-2(L)(2)(cppa)] center dot 2H(2)O (6) [HL = 3,5-di(imidazol-1-yl)benzoic acid, H(2)dpa = diphenic acid, H(2)chda = 1,4-cyclohexane-dicarboxylic acid, H(2)dc = 1,4-benzenediacrylic acid, H(2)cca = 4-carboxycinnamic acid, H(2)cppa = 3-(4-carboxyphenyl)propionic acid] have been obtained under hydrothermal conditions. Complexes I 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 LIS 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 mu-O and/or O-C-O linkages.