Coordination Polymers Self-Assembling from Cadmium(II) Ions and Flexible Pyridine-Based Bridging Ligands

Abstract

Abstract This paper describes coordination polymers assembled from cadmium nitrate and flexible bridging ligands, py–X–py (py = 4-pyridyl, 1a: X = CH2, 1b: X = C(=CH2), 1c: X = CH2CH2). The X-ray structure analysis of these complexes showed that their infinite topologies are quite different from each other, despite the structural similarity of ligands 1a—1c. Upon treatment with Cd(NO3)2, 1a gave an infinite two-dimensional sheet structure with a stoichiometry of ML2 (M and L denote metal and ligand, respectively). Ligand 1b also afforded an infinite polymer possessing the same ML2 composition. However, the polymer structure is characterized by one-dimensionally bounded macrocyclic frameworks where adjacent Cd ions are linked by two ligand molecules. Interestingly, ligand 1c gave an infinite polymer of M2L3 composition whose structure was shown to be a unique one-dimensional framework having macrocyclic frameworks (M2L2) linked together by the third L molecules.