An In Situ High-Temperature Single-Crystal Investigation of a Dehydrated Metal-Organic Framework Compound and Field-Induced Magnetization of One-Dimensional Metal-Oxygen Chains

catena-Poly[[bis-(methanol-κO)bis-(pyridine-κN)nickel(II)]-μ-tetra-fluoro-terephthalato-κO:O']

In the title compound, [Ni(C(8)F(4)O(4))(C(5)H(5)N)(2)(CH(4)O)(2)](n), the Ni(II) ion is located on an inversion center and is coordinated by four O atoms [Ni-O = 2.079 (4) Å] from two tetra-fluoro-terephthalate ligands and two methanol mol-ecules, and by two N atoms [Ni-N = 2.127 (4) Å] from two pyridine ligands in a distorted octa-hedral geometry. The Ni(II) ions are connected via the tetra-fluoro-terephthalate anions into a one-dimensional chain running along the crystallographic [011] direction.

Structural changes and coordinatively unsaturated metal atoms on dehydration of honeycomb analogous microporous metal-organic frameworks

Porous metal-organic framework compounds with coordinatively unsaturated metal sites on the inner surface of the pores promise to be valuable adsorbents and catalyst systems, either in industrial applications or as model systems to study interactions with guest molecules. The dehydration process of two isostructural microporous coordination polymers, [M2(dhtp)(H2O)2].8 H2O, termed CPO-27-M (M=Co, Zn; H(4)dhtp=2,5-dihydroxyterephthalic acid) was investigated by in situ variable temperature X-ray diffraction. Both compounds contain accessible coordination sites at the metal after complete removal of the solvent. However, despite the analogy of their crystal structures, they behave differently during dehydration. For CPO-27-Co, water desorption is a smooth topotactic process of second order with no concomitant space group change and no increase in microstrain, which is beneficial for the applicability of the material. Removal of the water propagates from the center of the channels outwards. The coordinating water molecule at the metal desorbs only when almost all the bulk water in the pores has disappeared. In contrast, discontinuities in the powder pattern of CPO-27-Zn indicate the occurrence of first-order transitions. The crystal structures of four of the five individual phases could be determined. The structure of the intermediate phase occurring just before the framework is completely evacuated was elusive in respect to full structure solution and refinement, but it is most probably related to the removal of the axis of threefold symmetry. The zinc-based material experiences a significant amount of strain.

Reversible Transformation of ZnII Coordination Geometry in a Single Crystal of Porous Metal-Organic Framework [Zn3(ntb)2(EtOH)2]⋅4 EtOH

A 3D porous metal-organic framework [Zn3(ntb)2(EtOH)2]n.4nEtOH (1) that generates 1D channels of honeycomb aperture has been prepared by the solvothermal reaction of Zn(NO3)(2).6 H2O and 4,4',4''-nitrilotrisbenzoic acid (H3NTB) in EtOH at 110 degrees C. Framework 1 exhibits reversible single-crystal-to-single-crystal transformations upon removal and rebinding of the coordinating EtOH as well as the EtOH guest molecules, which give rise to desolvated crystal [Zn3(ntb)2]n (1') and resolvated crystal [Zn3(ntb)2-(EtOH)2]n.4nEtOH (1''). The X-ray structures indicate that 3D host framework is retained during the transformations from 1 to 1' and from 1' to 1'', but the coordination geometry of ZnII ions changes from/to trigonal bipyramid to/from tetrahedron, concomitant with the rotational rearrangement of a carboxylate plane of the NTB3- relative to its associated phenyl ring. To retain the single crystal integrity, extensive cooperative motions must exist between the molecular components throughout the crystal. Framework 1' exhibits permanent porosity, thermal stability up to 400 degrees C, and blue luminescence, and high storage capabilities for N2, H2, CO2, and CH4.

Synthesis, Structural Characterization, Gas Sorption and Guest-Exchange Studies of the Lightweight, Porous Metal−Organic Framework α-[Mg3(O2CH)6]

Unsolvated magnesium formate crystallizes upon reaction of the metal nitrate with formic acid in DMF at elevated temperatures. Single-crystal XRD studies reveal the formation of [Mg3(O2CH)6 [symbol: see text] DMF], 1, a metal-organic framework with DMF molecules filling the channels of an extended diamondoid lattice. The DMF molecules in 1 can be entirely removed without disruption to the framework, giving the guest-free material alpha-[Mg3(O2CH)6], 2. Compound 2 has been characterized by both powder and single-crystal XRD studies. Thermogravimetric analyses of 1 show guest loss from 120 to 190 degrees C, with decomposition of the sample at approximately 417 degrees C. Gas sorption studies using both N2 and H2 indicate that the framework displays permanent porosity. The porosity of the framework is further demonstrated by the ability of 2 to uptake a variety of small molecules upon soaking. Single-crystal XRD studies have been completed on the six inclusion compounds [Mg3(O2CH)6 [symbol: see text] THF], 3; [Mg3(O2CH)6 [symbol: see text] Et2O], 4; [Mg3(O2CH)6 [symbol: see text] Me2CO], 5; [Mg3(O2CH)6 [symbol: see text] C6H6], 6; [Mg3(O2CH)6 [symbol: see text] EtOH], 7; and [Mg3(O2CH)(6) [symbol: see text] MeOH], 8. Analyses of the metrical parameters of 1-8 indicate that the framework has the ability to contract or expand depending on the nature of the guest present.

Hydrogen adsorption in a nickel based coordination polymer with open metal sites in the cylindrical cavities of the desolvated framework

The solvent contained within the cylindrical one-dimensional pores of the novel three-dimensional metal organic framework Ni2(dhtp)(H2O)2.8H2O can be removed without decomposition of the network, allowing gas storage within the cavities.

A scandium coordination polymer constructed from trimeric octahedral building blocks and 2,5-dihydroxyterephthalate

Scandium chloride and nitrate react with 2,5-dihydroxyterephthalic acid to form three-dimensional framework compounds in which hexagonally-closed packed inorganic building blocks are linked by the carboxylate groups of the organic ligand. The inorganic moieties consist of three scandium oxygen octahedra that are joined by a common mu3-oxygen atom; the pores in the structure account for 60% of the volume, but the framework decomposes upon removal of the solvent molecules.

A robust microporous 3D cobalt(ii) coordination polymer with new magnetically frustrated 2D lattices: single-crystal transformation and guest modulation of cooperative magnetic properties

A microporous 3D cobalt(II) coordination polymer featuring pillared layers [Co(2)(ma)(ina)](n) x 2nH(2)O (1 x 2H(2)O) (ma = malate, ina = isonicotinate) was generated by hydrothermal treatment with a void volume of 25.8%, in which the in-situ generated ma ligands connect the Co(II) ions into a 2D lattice with mixed and multiple exchange-bridges, affording a new geometrical topology different from the Kagomé lattice and leading to spin frustration. The rigid ina-pillared metallic-layered structure could retain 3D structural ordering upon guest removal and exchange. By soaking guest-free host in MeOH and methanamide (HCONH(2)) solutions, single crystals of dehydrated were transformed into single crystals of 1 x MeOH and 1 x HCONH(2), respectively, without apparent host-structural changes. 1 can also be rehydrated into 1 x 2H(2)O'. The guest-inclusion crystals have been characterized by X-ray single-crystal diffraction at 293 K and 93 K, confirming the single-crystal-to-single-crystal transformations and providing detailed information of the guest molecules confined in the subnanospace and host-guest and/or guest-guest hydrogen-bonding interactions. The magnetic behaviours of this family of porous magnetic materials are complex due to the influences of multiple metal sites, intra- and inter-layer exchanges, spin-orbit coupling, as well as geometrical frustration, which show magnetic ordering at <2 K, 3.5 K, 3.5 K, and 8 K for 1, 1 x MeOH, 1 x HCONH(2), and 1 x 2H(2)O, respectively, due to the different size of guest molecules along with the different host-guest interaction, which may slightly modify the path of magnetic exchange, decrease the intensity of the spin-frustration in the 2D lattice, and cooperatively enhance the magnetic ordering temperature.

The first route to large pore metal phosphonates

The first large pore (free diameter > 7 A) metal phosphonates have been prepared as divalent metal N,N'-piperazinebis(methylenephosphonate)s that possess pores greater than ca. 10 A in free diameter, are stable up to 400 degrees C and offer a route to chiral adsorbents and catalysts.

A lanthanide metal–organic framework with high thermal stability and available Lewis-acid metal sites

A lanthanide metal-organic framework, Dy(BTC)(H2O).DMF, with excellent thermal stability shows a high surface area, 655 m(2) g(-1), high hydrogen and carbon dioxide storage capability, and available Lewis-acid metal sites which could be anticipated to use in catalysis and metal-site specific chemical sensor.