Structure and Topology Versatility of Metal−Organic Frameworks Based on Tetradentate Ligands Isolated from Hydrothermal Metal/Ligand Reactions

The use of the planar tetradentate ligands 1,2,4,5-tetra(4-pyridyl)benzene (bztpy) and 1a,4a-dihydroxy-1e,2e,4e,5e-tetra(4-pyridyl)cyclohexane (chtpy) obtained by hydrothermal in situ metal/ligand reactions enabled the isolation of three metal−organic frameworks (MOFs) related to ligand-influencing factors with the formulas α-[CdCl2(bztpy)]·H2O (1), β-[CdCl2(bztpy)]·H2O (2), and [Cd4(O2CPh)2Cl2(OH)(chtpy)2(H2O)2](NO3)3·4.5H2O (3). 1 and 2 are two supramolecular isomers featuring a two-dimensional (2D) (4,4) net and three-dimensional (3D) NbO net that result from the conformational freedom of the bztpy ligands. 3 has a novel 3D MOF structure based on cuboidal {Cd4} clusters. The high-connected {Cd4} clusters connected to each other through planar tetradentate ligands in 3 ensured its uncommon (4,8)-connected scu topology. A discussion of the crystal structures, as well as the coordination behavior of the special tetradentate ligands upon differences geometries of the central connector, is provided.