David S. Wragg

Exceptional Behavior over the Whole Adsorption−Storage−Delivery Cycle for NO in Porous Metal Organic Frameworks

Two porous metal organic frameworks (MOFs), [M2(C8H2O6)(H2O)2] x 8 H2O (M = Co, Ni), perform exceptionally well for the adsorption, storage, and water-triggered delivery of the biologically important gas nitric oxide. Adsorption and powder X-ray diffraction studies indicate that each coordinatively unsaturated metal atom in the structure coordinates to one NO molecule. All of the stored gas is available for delivery even after the material has been stored for several months. The combination of extremely high adsorption capacity (approximately 7 mmol of NO/g of MOF) and good storage stability is ideal for the preparation of NO storage solids. However, most important is that the entire reservoir of stored gas is recoverable on contact with a simple trigger (moisture). The activity of the NO storage materials is proved in myography experiments showing that the NO-releasing MOFs cause relaxation of porcine arterial tissue.

Microwave-assisted synthesis of anionic metal–organic frameworks under ionothermal conditions

Two new isostructural coordination polymers with novel anionic metal-organic frameworks are synthesized under microwave conditions using an ionic liquid EMIm-Br as solvent and template.

The synthesis of gallium phosphate frameworks with and without fluoride ions present: attempts to direct the synthesis of double four-ring containing materials

During attempts to synthesise gallium phosphate materials containing the double four-ring building unit, three pyridine-templated gallium fluorophosphates and one pyridine-templated gallium phosphate were prepared and their structures solved using single crystal X-ray diffraction experiments. None of the three fluorophosphates contained the double four-ring unit, while the material prepared in the absence of fluoride did. This overturns some of the conventional wisdom that fluoride is necessary to specifically form the double four-ring unit. The synthetic conditions needed to prepare the materials and possible relationships between the building units found in the solids are discussed.

Highly cis-Selective Rh(I)-Catalyzed Cyclopropanation Reactions

The performance of recently reported highly cis-diastereoselective Rh(I) cyclopropanation catalysts has been significantly improved by a systematic study of different reaction parameters (catalyst activation, solvent, temperature, stoichiometry). The catalyst efficiency and diastereoselectivity were enhanced by changing the activating agent from AgOTf to NaBArf. With this new system, the Rh(I) catalyst was shown to be a highly efficient and cis-diastereoselective cyclopropanation catalyst in reactions between α-diazoacetates and a range of different alkenes and substituted derivatives. Particularly noteworthy is the remarkable reactivity and cis-diastereoselectivity displayed in the reactions between ethyl diazoacetate and cyclopentene, 2,5-dihydrofuran, and benzofuran, with yields up to 99% and cis-selectivities greater than 99%.

Ionothermal synthesis of inorganic–organic hybrid materials containing perfluorinated aliphatic dicarboxylate ligands

Two new hybrid inorganic-organic frameworks containing perfluorinated dicarboxylate ligands have been synthesized ionothermally from a mixture of 1-ethyl-3-methylimidazolium bromide (emim-Br), and triflimide (emim-Tf(2)N). The cobalt(ii) tetrafluorosuccinate, [emim](2)[Co(H(2)O)(2)(O(2)CCF(2)CF(2)CO(2))(2)] (), is a two-dimensional coordination polymer containing anionic framework layers separated by emim cations. When hexafluoroglutaric acid is used in similar reactions, [emim](2)[Co(3)(O(2)CCF(2)CF(2)CF(2)CO(2))(4)(H(2)O)(4)] () forms. Like , this phase contains anionic layers of cobalt and the fluorinated carboxylate separated by emim cations. These new phases represent the first examples of ionothermally synthesized materials using perfluorinated aliphatic carboxylates.

The synthesis and modification of aluminium phosphonates

Two synthetic approaches to the preparation of mixed aluminium phosphite-phosphonate solids have been made. First, the hydrothermal reaction of aluminium hydroxide (gibbsite) with mixtures of phosphorous and methylphosphonic acids under conditions that give microporous aluminium methylphosphonate-β (AlMePO-β) when methylphosphonic acid alone is used, and secondly, the reaction of AlMePO-β with increasing amounts of molten phosphorous acid. Under hydrothermal conditions there is no evidence that AlMePO-β can be prepared with phosphite groups randomly replacing methylphosphonate groups. Rather, the products are dominated over the intermediate phosphite/phosphonate compositional range by a novel phase that is thought, on the basis of 27 Al and 31 P MAS NMR and FTIR spectroscopies, to contain differing amounts of phosphite and methylphosphonate groups. Reaction of AlMePO-β with levels of molten phosphorous acid at 40% or more of the methylphosphonate content gives mixtures of AlMePO-β and a new phosphite phase, whereas reaction using lower amounts of the molten acid leaves AlMePO-β as the only X-ray visible phase. Extension of the melt method to the separate reaction of gibbsite with methylphosphonic and phosphorous acids yields, respectively, single crystals of a new aluminium methylphosphonate [Al(O 3 PCH 3 )(HO 3 PCH 3 )·H 2 O] and a known aluminium phosphite [Al 2 (O 3 PH) 3 ·4H 2 O], the structure of which had only been solved from powder diffraction data. Single crystal diffractometry improved the accuracy with which the structural parameters of the phosphite are known and enabled structure solution of the new aluminium methylphosphonate [Pnma, a=19.075(6) A, b=5.117(2) A, c=8.439(2) A], which is made up of layers that contain isolated, octahedrally coordinated aluminium linked by methylphosphonate groups.

Unit cell thick nanosheets of zeolite H-ZSM-5: Structure and activity

Nanosheets of zeolite H-ZSM-5 were synthesized and characterized by X-ray diffraction, transmission electron microscopy (TEM), N2-physisorption, FT-IR spectroscopy, 27Al and 29Si MAS NMR spectroscopy in addition to catalytic testing in conversion of methanol to hydrocarbons (MTH). It was found that Rietveld analysis, involving anisotropic broadening parameters, gave average crystallite dimensions in good agreement with TEM images. The selectivities in MTH is intact in the mesoporous nanosheet H-ZSM-5 with the largest difference being a higher C3/C2 ratio compared to regular H-ZSM-5.

Copper Phosphonatoethanesulfonates: Temperature Dependent in Situ Energy Dispersive X-ray Diffraction Study and Influence of the pH on the Crystal Structures

The system Cu(2+)/H2O3P-C2H4-SO3H/NaOH was investigated using in situ energy dispersive X-ray diffraction (EDXRD) to study the formation and temperature induced phase transformation of previously described copper phosphonosulfonates. Thus, the formation of [Cu2(O3P-C2H4-SO3)(OH)(H2O)]·3H2O (4) at 90 °C is shown to proceed via a previously unknown intermediate [Cu2(O3P-C2H4-SO3)(OH)(H2O)]·4H2O (6), which could be structurally characterized from high resolution powder diffraction data. Increase of the reaction temperature to 150 °C led to a rapid phase transformation to [Cu2(O3P-C2H4-SO3)(OH)(H2O)]·H2O (1), which was also studied by in situ EDXRD. The comparison of the structures of 1, 4, and 6 allowed us to establish a possible reaction mechanism. In addition to the in situ crystallization studies, microwave assisted heating for the synthesis of the copper phosphonosulfonates was employed, which allowed the growth of larger crystals of [NaCu(O3P-C2H4-SO3)(H2O)2] (5) suitable for single crystal X-ray diffraction. Through the combination of force field calculations and Rietveld refinement we were able to determine the crystal structure of [Cu1.5(O3P-C2H4-SO3)] 2H2O (3) and thus structurally characterize all compounds known up to now in this well investigated system. With the additional structural data we are now able to describe the influence of the pH on the structure formation.

Ionothermal synthesis, structure and characterization of three-dimensional zinc phosphates.

The first metal phosphate analogue of the zeolite Na-J (framework type JBW) has been synthesized by an ionothermal approach along with zincophosphate thomsonite.

Solvothermal aluminophosphate zeotype synthesis with ionic liquid precursors

We have carried out a study of aluminophosphate framework synthesis using several amine based ionic liquids and their parent amines as solvent and template. The results suggest that in the presence of fluoride ions from hydrofluoric acid the ionic liquids and their parent amines produce the same frameworks, while in synthesis without fluoride ions the products are not related. The results include the synthesis and crystal structure of a novel extra-large pore material using 1-methylpyrrolidine as solvent and template. The relationship between this and sodalite, which can be synthesised in cobalt aluminophosphate form using an ionic liquid prepared from 1-methylpyrrolidine is described. The crystal structures of two other new layered materials are also presented.