Abstract
The synthesis, structure and some properties of the one-dimensional coordination polymer, [Pr2(pdc)3(Hpdc)]n·n(H3hp)·8n(H2O), (H2pdc = pyridine 2,6-dicarboxylic acid, C7H5NO4; 3hp = 3-hydroxypyridine, C5H5NO) are described. One of the Pr3+ ions is coordinated by two O,N,O-tridentate pdc2− ligands and one tridentate Hpdc− anion to generate a fairly regular PrO6N3 tri-capped trigonal prism, with the N atoms acting as the caps. The second Pr3+ ion is coordinated by one tridentate pdc2− dianion, four water molecules and two monodentate bridging pdc2− ligands to result in a PrO8N coordination polyhedron that approximates to a mono-capped square-anti-prism. The ligands bridge the metal-atom nodes into a chain, which extends in the [100] direction. The H3hp+ cation and uncoordinated water molecules occupy the inter-chain regions and an N–HLO and numerous O–HLO hydrogen bonds consolidate the structure. The H3hp+ species appears to intercalate between pendant pdc rings to consolidate the polymeric structure. Crystal data: 1 (C33H43N5O29Pr2), Mr = 1255.54, triclinic, (No. 2), Z = 2, a = 13.2567(1) Å, b = 13.6304(2) Å, c = 13.6409(2) Å, α = 89.695(1)°, β = 63.049(1)°, γ = 86.105(1)°, V = 2191.16(5) Å3, R(F) = 0.033, wR(F2) = 0.084.
Highlights
Coordination polymers with potentially useful physical properties such as sorption and catalytic activity can be produced by careful choice of ligands, metal ions, the solvent and the pH of the solution [1,2,3]
The coordination geometries of the praseodymium ions in 1 are very different: Pr1 is coordinated by two O,N,O-tridentate pdc2− dianions and the O,N,O-tridentate Hpdc− anion to generate a fairly regular tri-capped trigonal prismatic PrO6N3 coordination geometry with the N atoms serving as the caps protruding through the prismatic side-faces (Figure 2)
The Pr2 species in 1 is coordinated by an O,N,O-tridentate pdc2− dianion, four water molecules and two bridging monodentate-O pdc− species to generate a PrO8N coordination polyhedron that approximates to a mono-capped square anti-prism (Figure 3)
Summary
Coordination polymers with potentially useful physical properties such as sorption and catalytic activity can be produced by careful choice of ligands, metal ions, the solvent and the pH of the solution [1,2,3]. Pyridine-2,6-dicaboxylic acid (H2pdc, C7H5NO4) is a versatile ligand that can chelate to, or bridge between, metal ions and can furnish different types of infinite-chain polymers [4,5,6,7]. [Pr2(pdc)3(H2O)3]n·nH2O [9], [Pr3(pdc)4(Hpdc)(H2O)8]n·8nH2O [9] These show various ligand and water bonding modes to the metals, but all of them lead to nine-coordinate polyhedra for the metal atoms and the bridging ligands lead to infinite chains in the crystal
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