2012 Volume 85 Issue 10 Pages 1102-1111
We report on the synthesis, single-crystal structures, and properties (IR, UV–vis, ESR, and TG) of a series of coordination polymers employing R4-terephthalate dianion (R4-benzenedicarboxylate dianion, R4-bdc2−: R = H, F, Cl, Br) in which halogen atoms are systematically changed and 4,4′-bipyridine (4,4′-bpy) as cobridging ligands. These compounds are synthesized under the same conditions and all display octahedral metal coordination environments. A one-dimensional coordination polymer, [Mn(µ-4,4′-bpy)(H2O)4](H4-bdc) (1) consists of Mn(II) and 4,4′-bpy was obtained by reaction of Mn(II), terephthalate and 4,4′-bpy. Uncoordinated terephthalate acts as not only counter ion but also linker to form a three-dimensional network by hydrogen-bonding and π–π interactions. When halogen atoms are introduced to a benzene ring, layers of square-grid of octahedral Mn(II) ions are obtained for [Mn(µ-F4-bdc)(µ-4,4′-bpy)(H2O)2] (2), [Mn(µ-Cl4-bdc)(µ-4,4′-bpy)(H2O)2] (3), and [Mn(µ-Br4-bdc)(µ-4,4′-bpy)(H2O)2] (4). One of the major differences of the structures is hydrogen-bonding interactions between layers. This major difference is due to the different ionic radii of halogen atoms attached to benzene rings of the ligand to give different crystal packing. Compounds 2–4 exhibit different thermal behavior. While the XRD pattern of 2 indicates structural change upon hydration/dehydration, XRD patterns of 4 are not globally changed in these processes.
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