No abstract

An assembly of three metal coordination polymers (CPs), [M(bipy)(C4O4)(H2O)2]·3H2O (M = Mn (1), Fe (2), Zn (3), and bipy = 4,4′‐bipyridine, C4O42− (squarate) = dianion of H2C4O4 (squaric acid)), was synthesized and structurally characterized. Single‐crystal X‐ray structural determination reveals that compounds 1–3 are iso‐structural, in which the M(II) ions are six‐coordinate in a distorted octahedral geometry. C4O42− and bipy both act as bridging ligands with bis‐monodentate coordination mode connecting the M(II) ions to form a two‐dimensional (2D) layered metal–organic framework (MOF). Adjacent 2D layers are then arranged in parallel and interpenetrated manners to construct their three‐dimensional (3D) supramolecular architecture. Compounds 1, 2, and 3 undergo two‐step dehydration processes with the first and second weight losses of 14.1 and 8.6% for 1, of 12.1 and 7.5% for 2, and of 11.2 and 8.1% for 3, respectively, corresponding to the weight losses of the three guest water molecules and the two coordinated water molecules, and all exhibit reversible sponge‐like water de/adsorption properties during de/rehydration processes for guest water molecules as per cyclic thermogravimetric analysis (TGA). The single‐crystal‐to‐single‐crystal (SCSC) structural transformation during the reversible de/rehydration processes of three guest water molecules was identified and monitored using exhaustive single‐crystal and powder X‐ray diffraction measurements.

In anti‐anti‐anti‐anti‐ oder syn‐syn‐syn‐syn‐Form kann der neue Ligand N,N′‐Bis(α‐pyridyl)‐2,6‐diaminopyridin (H2tpda) Metallionen binden (schematische Darstellung rechts). Mit tpda sind die fünfkernigen CoII‐ (Gegenion Cl−) und NiII‐Komplexe (Gegenion NCS−) zugänglich. Deren Metallkette ist helical von vier tpda‐Liganden umwunden.

Two extended coordination frameworks of CdII–squarate complexes with the formulas [Cd2(C4O4)2.5(H2O)4](dpaH)·1.5(H2O) (1) and [Cd(C4O4)(dpa)(H2O)] (2) (dpa = 2,2′‐dipyridylamine) have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction studies. Structural determination reveals that compound 1 consists of a free monoprotonated 2,2′‐dipyridylamine ion (dpaH+) and a two‐dimensional (2D) anionic, layered framework, {[Cd2(C4O4)2.5(H2O)4]–}, which is formed with two antiprismatic square‐boxes as the fundamental building unit through the connection between CdII ions and hybrid μ1,2,3‐, μ1,2,3,4‐squarates. Each square‐box acts as a host for the inclusion of one pyridine ring of dpaH+. Adjacent dpaH+ cations are then self‐assembled by the parallel alignment of the other pyridine ring of dpaH+ to complete a 3D network with one‐dimensional (1D) channels intercalated by water molecules. Compound 2 contains a distorted octahedral CdII center coordinated by two squarates, two waters and one dpa ligand to form a 1D 2‐legged, ladder‐like framework by the connection of a [Cd(dpa)(μ2‐H2O)]24+ dimeric unit and a μ1,2‐squarate. Weak π–π stacking interaction and hydrogen bonds of N–H···O, O–H···O and C–H···O among the squarate, water and dpa ligands provide additional intra‐ and intermolecular interactions on the stabilization of these two polymeric frameworks. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A chiral nickel histidine compound, [Ni(L-his) 2 ]×H 2 O (1, L-his = anion of L-histidine), was synthesized in high yield from the reaction of Ni(OAc) 2 ×4H 2 O and L-histidine in the presence of 4,4¢-bipyridine under mild reaction conditions. A single-crystal X-ray diffraction analysis showed that compound 1 crystallizes in the monoclinic system, space group C2, with a chemical formula of C 12 H 18 N 6 NiO 5 , cell parameters: a = 29.416(2) Å, b = 8.2667(7) Å, c = 6.3137(5) Å, b = 90.066(2)°, V = 1535.3(2) Å 3 and Z = 4. Each nickel(II) ion in 1 is six coordinated, bonded to two oxygen donors and four nitrogen donors from two crystallographically independent L-his -ligands with a tridentate coordination mode to form a monomeric species. Monomeric forms of 1 undergo self-assembly to form a three-dimensional (3D) supramolecular architecture via subtle combinations of N-H×××O type hydrogen bonding interactions among the adjacent L-his -ligands and p-p stacking interactions among the imidazole rings of the L-his -ligands. The supramolecular entity exhibits an unusually high thermal stability, at temperatures of up to 360°C and shows reversible de-/re-hydration properties.