Dimensionality Variation in Polymeric Metallo-Organic Frameworks

Single crystal X‐ray crystallography was used to determine the structures of four metallo‐organic complexes derived from pyridyl ligands and the metal ions, Cu2+, Zn2+ and Ag+. Two metallo‐organic layer framework structures (1 and 3), a strand (2) and a dimer (4) structure were formed when the tetradentate ligands, tetrakis(nicotinoxymethyl)methane (TNM) and tetrakis(isonicotinoxymethyl)methane (TINM), were reacted with the first and second row transition metal cations, copper, silver, and zinc. The choice of anion and ligand was found to affect the outcome of the structure. Contrary to our previous results with the same ligands and similar transition metal cations, no genuine 3D metallo‐organic frameworks (MOFs) were obtained. Several factors were found to affect MOF formation: the coordination geometry, the meta‐ or para‐configuration of the coordinating pyridyl moieties and the size and type of the counter anion. In 1, the use of TNM (with a shorter “coordination arm” than TINM), in combination with an octahedral coordination geometry (4 Py, SO42− and H2O) and a relatively large sulfate anion, leads to a sandwich‐like layer structure with the anions between the MOF layers. The layers have a thickness of 2.1 nm. In complex 3, similar layer structures are assembled from four‐ and five‐coordinate (2 Py, NO3−, H2O/2 Py, 3 NO3−) Ag+ ions with TINM and nitrate anions. However, in complex 2, the Zn2+ ion is tetrahedrally (2 Py, 2 Cl−) coordinated, creating an infinite strand structure. Most surprisingly, in complex 4, two arms of the ligand are uncoordinated and a binuclear square‐planar coordination geometry (2 Py, 2 CH3COO−) around the Cu2+ ions, as well as the acetate anions, create a non‐polymeric dimeric structure. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)