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PubMed2003

Effect of surface modification on hydration kinetics of carbamazepine anhydrate using isothermal microcalorimetry.

The purpose of this research was to improve the stability of carbamazepine (CBZ) bulk powder under high humidity by surface modification. The surface-modified anhydrates of CBZ were obtained in a specially designed surface modification apparatus at 60 degrees C via the adsorption of n-butanol, and powder x-ray diffraction, Fourier-Transformed Infrared spectra, and differential scanning calorimetry were used to determine the crystalline characteristics of the samples. The hydration process of intact and surface-modified CBZ anhydrate at 97% relative humidity (RH) and 40 +/-C 1 degrees C was automatically monitored by using isothermal microcalorimetry (IMC). The dissolution test for surface-modified samples (20 mg) was performed in 900 mL of distilled water at 37 +/-C 0.5 degrees C with stirring by a paddle at 100 rpm as in the Japanese Pharmacopoeia XIII. The heat flow profiles of hydration of intact and surface-modified CBZ anhydrates at 97% RH by using IMC profiles showed a maximum peak at around 10 hours and 45 hours after 0 and 10 hours of induction, respectively. The result indicated that hydration of CBZ anhydrate was completely inhibited at the initial stage by surface modification of n-butanol and thereafter transformed into dihydrate. The hydration of surface-modified samples followed a 2-dimensional phase boundary process with an induction period (IP). The IP of intact and surface-modified samples decreased with increase of the reaction temperature, and the hydration rate constant (k) increased with increase of the temperature. The crystal growth rate constants of nuclei of the intact sample were significantly larger than the surface-modified sample's at each temperature. The activation energy (E) of nuclei formation and crystal growth process for hydration of surface-modified CBZ anhydrate were evaluated to be 20.1 and 32.5 kJ/mol, respectively, from Arrhenius plots, but the Es of intact anhydrate were 56.3 and 26.8 kJ/mol, respectively. The dissolution profiles showed that the surface-modified sample dissolved faster than the intact sample at the initial stage. The dissolution kinetics were analyzed based on the Hixon-Crowell equation, and the dissolution rate constants for intact and surface-modified anhydrates were found to be 0.0102 +/-C 0.008 mg(1/3) x min(-1) and 0.1442 +/-C 0.0482 mg(1/3) x min(-1). The surface-modified anhydrate powders were more stable than the nonmodified samples under high humidity and showed resistance against moisture. However, surface modification induced rapid dissolution in water compared to the control.

1-Butanol↗
PubMed2005

Facilities for high-pressure research with the diamond anvil cell at GSECARS.

An overview of facilities for high-pressure research with the diamond anvil cell (DAC) at the GeoSoilEnviroCARS (GSECARS) sector at the Advanced Photon Source (Argonne, Illinois) is presented. There are three operational experimental stations (13-ID-C, 13-ID-D and 13-BM-D) where DAC instrumentation is installed for various types of experiments at high pressure and extreme temperature conditions. A fourth station (13-BM-C) is under construction and will be operational in 2006. While most X-ray diffraction experiments have been undertaken with powder samples so far, there is a growing demand for single-crystal diffraction (SCD) at high pressure. As one of the principal components at GSECARS, SCD is currently under rapid development. Other relevant techniques have also been developed for obtaining complementary information from powder or single-crystal samples at high pressure. For example, an on-line Brillouin system is installed and operational at 13-BM-D for acoustic velocity and single-crystal elasticity determinations. In addition, various X-ray spectroscopy techniques (e.g. X-ray emission and X-ray Raman) are employed for measuring electronic and magnetic properties. Future developments are discussed with the DAC program at GSECARS.

Journal Article↗
PubMed1997

Non-decay type fast-setting calcium phosphate cement: hydroxyapatite putty containing an increased amount of sodium alginate.

A hydroxyapatite [(HAP) Ca10(PO4)6(OH)2] putty that behaves like a putty or self-curing resin was made by increasing the amount of sodium alginate in non-decay type fast-setting calcium phosphate cement (nd-FSCPC). nd-FSCPC became viscous as the sodium alginate concentration was increased. The best handling properties were obtained when nd-FSCPC contained 8% sodium alginate in its liquid phase. When a 2-kg glass plate was placed on the paste, HAP putty spread to form an area three times that of FSCPC paste. Thus, HAP putty is expected to be easier to use than FSCPC in the filling of bone defects. HAP putty did not decay; in fact, it set within approximately 20 min when immersed in distilled water immediately after mixing. The wet diametral tensile strength value of HAP putty was approximately 12 MPa after 24 h, the same as that for nd-FSCPC containing 0.5% sodium alginate in its liquid phase, or FSCPC that is free from sodium alginate. The elements constituting set HAP putty were examined using powder X-ray diffraction and found to be predominantly apatitic minerals after 24 h. Since the handling properties of a putty or self-curing resin-like cement are very useful in certain surgical procedures, HAP putty made by increasing the sodium alginate concentration in nd-FSCPC is potentially a valuable new biomaterial for use in plastic and reconstructive surgery, as well as oral and maxillofacial surgery.

Alginates↗
PubMed1999

Histological and compositional evaluations of three types of calcium phosphate cements when implanted in subcutaneous tissue immediately after mixing.

To evaluate the soft tissue response of calcium phosphate cement (CPC), consisting of an equimolar mixture of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) under conditions close to those encountered in actual surgical procedures, we implanted three types of CPC [conventional CPC (c-CPC), fast-setting CPC (FSCPC), and antiwashout type FSCPC (aw-FSCPC; formerly called nondecay type FSCPC or nd-FSCPC)] subcutaneously in the abdomens of rats immediately (1 min) after mixing. At 1 week after surgery, histological examination and compositional analysis were performed using light microscopy and powder X-ray diffraction (XRD), respectively. The implanted c-CPC was crumbled completely, whereas FSCPC and aw-FSCPC retained their shape. Large vesicles containing copious inflammatory effusion were subcutaneously formed around the c-CPC. Histologically, many foreign-body giant cells were collected around the c-CPC, and moderate inflammatory cell infiltration was observed at 1 week after surgery. In contrast, the FSCPC and aw-FSCPC were covered with a thin layer of granulation tissue that included few giant cells and presented slight inflammatory cell infiltration, and no effusion was observed. The XRD analysis of the c-CPC revealed the presence of some unreacted DCPA even 1 week after implantation, whereas almost no DCPA was found in the FSCPC or aw-FSCPC. In conclusion, it was found that CPC does not always show excellent tissue response. When c-CPC is implanted subcutaneously in rats immediately after mixing, it fails to set and causes a severe inflammatory response. Therefore, the type of CPC should be chosen according to the clinical particulars. CPC should be used in a manner that assures its setting reaction. We recommend the use of FSCPC and aw-FSCPC for surgical applications, such as orthopedics, plastic and reconstructive surgery, and oral and maxillofacial surgery, where the cement might otherwise crumble due to the pressure before setting.

Animals↗
PubMed2000

Lead hydro sodalite [Pb2(OH)(H2O)3]2[Al3Si3O12]2: synthesis and structure determination by combining X-ray rietveld refinement, 1H MAS NMR FTIR and XANES spectroscopy.

Ion exchange of the sodium hydro sodalites [Na3(H2O)4]2-[Al3Si3O12]2 [Na4(H3O2)]2[Al3Si3O12]2 and [Na4(OH)]2[Al3Si3O12]2 with aqueous Pb(NO3)2 solutions yielded, whichever reactant sodalite phase was used, the same lead hydro sodalite, [Pb2(OH)-(H2O)3]2[Al3Si3O12]2. Thus, in the case of the non-basic reactant [Na3(H2O)4]2-[Al3Si3O12]2 an overexchange occurs with respect to the number of nonframework cationic charges. Rietveld structure refinement of the lead hydro sodalite based on powder X-ray diffraction data (cubic, a = 9.070 A, room temperature, space group P43n) revealed that the two lead cations within each polyhedral sodalite cage form an orientationally disordered dinuclear [Pb2(micro-OH)(micro-H2O)(H2O)2]3+ complex. Due to additional lead framework oxygen bonds the coordination environment of each metal cation (CN 3+3) is approximately spherical, and clearly the lead 6s electron lone pair is stereochemically inactive. This is also suggested by the absence of a small peak at 13.025 keV, attributed in other Pb2+-O compounds to an electronic 2p-6s transition, in the PbL3 edge XANES spectrum. 1H MAS NMR and FTIR spectra show that the hydrogen atoms of the aqua hydroxo complex (which could not be determined in the Rietveld analysis) are involved in hydrogen bonds of various strengths.

Journal Article↗
PubMed2001

Effect of added NaHCO3 on the basic properties of apatite cement.

Alternation of a composition of set apatite cement (AC) from carbonate-free apatite (CO3-free AP) to carbonate apatite (CO3-AP) may accelerate replacement of the set AC with bone because CO3-AP can be dissolved much faster than CO3-free AP in the weak acidic solution produced by osteoclasts. In this investigation, NaHCO3 was added to the AC component and the effects of added NaHCO3 on cement-setting behavior and on set mass were studied as an initial step for the fabrication of AC, which can be replaced with bone faster than current AC. When NaHCO3 was added to AC, the resultant set mass contained CO3. Although not all CO3 was incorporated in the set AC, the amount of CO3 incorporated into the set AC increased with the amount of added NaHCO3. Powder X-ray diffraction analysis and Fourier transform infrared spectrometer measurements revealed the formation of B-type CO3-AP. The setting time measured in an incubator at 37 degrees C and 100% relative humidity slowed from 30 to 45 min, indicating that NaHCO3 has an inhibitory effect on AP formation. The diametral tensile strength of the set AC decreased significantly with the addition of NaHCO3. Scanning electron microscopic observation revealed that fine crystals were formed in the set AC when NaHCO3 was added to AC. As a result, the crystallinity indices of the set AC measured using X-ray diffraction and Fourier transform infrared spectroscopy decreased with an increase in the amount of added NaHCO3. The dissolution rate of set AC in weak acid, pH 5.5, increased with the amount of added NaHCO3. We concluded that the formation of B-type CO3-AP and the resulting faster dissolution of set AC in weak acidic solution is preferable for the faster replacement of set AC with bone even though the decreased diametral tensile strength value is a shortcoming.

Apatites↗
PubMed2001

Note: dissolution of aerosol particles of budesonide in Survanta, a model lung surfactant.

The effect of a pulmonary surfactant extract from bovine lung, Survanta, on the dissolution rate of aerosol particles of budesonide was determined. Aerosol particles of budesonide were generated from an ethanol solution, dried, and collected by a cascade impactor for characterization or by a liquid impinger for dissolution experiments. Powder x-ray diffraction, differential scanning calorimetry, differential thermal analysis, and scanning electron microscopy were used to characterize the aerosol particles and starting material. No change in phase was detected, although the aerosol particles appeared to contain residual solvent. The dissolution rate of the aerosol particles in saline was low and variable. Survanta increased the extent of dissolution of budesonide in proportion to the added concentration, which was also verified by equilibrium solubilization studies. Survanta also increased rate of dissolution, in a manner similar to sodium dodecyl sulfate. Analysis of the concentration of budesonide following ultracentrifugation indicated that there is rapid equilibration of budesonide between the Survanta and aqueous phase. These results show that lung surfactant has the potential of enhancing the rate and extent of dissolution of drugs administered to the lung.

Aerosols↗
PubMed2001

Solid-state transformations of zinc 1,4-benzenedicarboxylates mediated by hydrogen-bond-forming molecules.

The zinc 1,4-benzenedicarboxylates [Zn3(bdc)3(H2O)3] . 4 DMF (1; bdc = 1,4-benzenedicarboxylate), [Zn(bdc)(H2O)] . DMF (2), and [Zn(bdc)] DMF (3) crystallise at room temperature from mixtures of toluene/ dimethylformamide (DMF) under concentrated, dilute and dry conditions, respectively. The structure of phase 1 (monoclinic: P2(1)/c, a 13.065(1), b = 9.661(1), c = 18.456(1) A, beta = 106.868(2) degrees) consists of layers containing stacks of three zinc cations linked by mono- and bidentate bdc groups. Structure 1 converts to the known phase 2 by an irreversible, reconstructive phase transformation, whereas 2 and 3 interconvert reversibly upon the loss or addition of water. Removal of all solvent molecules included during crystallisation gives poorly crystalline [Zn(bdc)] (4), which is readily converted to highly crystalline solids upon contact with hydrogen-bond-forming molecules such as water, DMF and small alcohols. The crystal structures of the mono- and dihydrates [Zn(bdc)(H2O)] (6) and [Zn(bdc)-(H2O)2] (7) have been determined ab initio from powder X-ray diffraction data (compound 6, monoclinic: C2/c, a = 17.979(1), b = 6.352(1), c = 7.257(1) A, beta=91.477(1) compound 7, monoclinic: C2/c, a = 14.992(1), b = 5.0303(2), c = 12.098(1) A, beta = 103.82(1) degrees). The methanol adduct [Zn3(bdc)3] . 6CH3OH (5) is the same as that prepared previously by direct crystallisation. Comparison of these adduct structures with those prepared directly reveal that they are formed by in situ recrystallisations. Subsequent removal of included molecules gives amorphous [Zn(bdc)], which can be recrystallised again when placed in contact with hydrogen-bond-forming molecules.

Journal Article↗
PubMed2002

Anion exchange in the channels of a robust alkaline earth sulfonate coordination network.

The barium sulfonate network presented herein, [[Ba2(L)(H2O)5]Cl]infinity (1), represents the first metal sulfonate compound to possess a cationic framework. The network is layered with channels between pillaring ligands in which chloride ions reside. Compound 1 contracts slightly upon dehydration but retains its overall structural motif to 420 degrees C. Significantly, the chloride ions of the structure can be exchanged in 80% yield for fluoride ions in a facile manner. This exchange is quantified by elemental analyses, gravimetric determination, and 19F NMR spectroscopy. Confirmation of retention of structure is provided by standardized powder X-ray diffraction experiments. This last point is notable as the F-analogue of the structure is not attainable by a direct synthesis. These results illustrate one of the hallmark features of supramolecular chemistry, that a robust and functional framework can result through cooperative interactions between more weakly interacting units.

Journal Article↗
PubMed2002

Modulation of the intercalation properties of copper-zinc mixed-metal phosphonate materials.

New layered mixed divalent metal vinylphosphonates Cu(II) (1-x)Zn(II) (x)(O(3)PC(2)H(3)).H(2)O have been prepared from a range of pre-formed copper-zinc oxides Cu(II) (1-x)Zn(II) (x)O obtained by isomorphous substitution of zinc into the tenorite-type structure of Cu(II)O. The corresponding mixed divalent copper-zinc vinylphosphonates have been characterised by powder X-ray diffraction, elemental analysis, infrared spectroscopy and thermogravimetric analysis. All compounds have been shown to consist of a single-phase solid solution that crystallises in an monoclinic unit cell, space group P2(1)/c with a=9.86-9.90, b=7.61-7.64, c=7.32-7.35 A and beta=95.9-96 degrees, with the exception of the pure zinc vinylphosphonate (x=1), the structure of which is comparable to other Zn(II)(O(3)PR).H(2)O materials. Studies of the intercalation of n-butylamine into the range of copper-zinc vinylphosphonates have demonstrated that significant modulation of the adsorption properties occurs; whereas one mole of amine is intercalated into the pure zinc vinylphosphonate to give Zn(II)(O(3)PC(2)H(3)).(C(4)H(9)NH(2)), for all other members of the series two moles of amine are coordinated to give intercalated compounds of composition Cu(II) (1-x)Zn(II) (x)(O(3)PC(2)H(3)).[(C(4)H(9)NH(2))(1-x)(C(4)H(9)NH(2))(x)](2) from which the amine can be sequentially removed from the different metal sites; this opens up possibilities for further applications of these materials.

Journal Article↗
PubMed1988

Ovine ceroid-lipofuscinosis II: Pathologic changes interpreted in light of biochemical observations.

Ceroid-lipofuscinosis is studied in a breed of sheep and the histochemical and ultrastructural changes are interpreted in light of the known chemical composition of cytosomes. It is concluded that the ovine disease is a lysosomal proteinosis. It is postulated that the multilamellar arrays reflect a complex three-dimensional structure of alternating lipid and protein with the proteinaceous component being specific polypeptides. This is supported by powder X-ray diffractions at 10A implying a repeating proteinaceous unit in the structures. The coherent size of diffracting units was remarkably similar to the periodicity of lamellae observed in electron micrographs of lipopigment cytosomes. The fluorescent and staining characteristics of lipopigment can be explained by the above conclusion and postulate.

Animals↗
PubMed2005

Synthesis and secondary structure of oligo(alpha-isobutyl beta,L-aspartate)s.

The oligo(beta-peptide)s, hexa(alpha-isobutyl beta,L-aspartate) (Hex-AIBLA) and octa(alpha-isobutyl beta,L-aspartate) (Oct-AIBLA), were synthesized in solution by using standard coupling methods. Powder x-ray diffraction showed that the octamer crystallized in the two helical crystal forms known to exist in the homologous poly(beta-peptide), whereas the hexamer seemed to adopt an extended conformation. Both CD and 1H-NMR spectra of Oct-AIBLA in MeOH revealed the presence of a regularly folded conformation in this solvent, presumably the 3(14) helix. The helix-to-coil transition of Oct-AIBLA was observed to take place upon heating in both MeOH and CHCl3, in the second case associated with a not-well-defined aggregation-disaggregation process. The spectroscopic evidence obtained on the presence of folded structures in Hex-AIBLA were much weaker than for the octamer.

Circular Dichroism↗
PubMed2003

Molecular structure-activity relationships for the oxidation of organic compounds using mesoporous silica catalysts derivatised with bis(halogeno)dioxomolybdenum(VI) complexes.

Mo K-edge XAFS spectra have been measured for ordered mesoporous silica MCM-41 grafted with the complexes [MoO2X2(thf)2] (X=Cl, Br). For grafting reactions in the absence of triethylamine, materials with 1 wt. % Mo are obtained; the Mo K-edge EXAFS results indicate the co-existence of isolated surface-fixed monomeric species [MoO2[(-O)3SiO]2(thf)(n)] and [MoO2[(-O)3SiO]X(thf)(n)]. When Et3N is used in the grafting reactions, materials with 4 wt. % Mo are obtained. The EXAFS data for the material prepared using [MoO2Cl2(thf)2] and Et3N indicate the presence of dinuclear species with two Mo(VI) centres, each with two Mo=O groups and each linked by one or two oxo bridges (Mo...Mo 3.27 A). The molybdenum centres in the material prepared using the dibromo complex comprise mainly isolated four-coordinate dioxomolybdenum(VI) and trioxomolybdenum(VI) monomeric species, with a small contribution from dimeric species. All materials were further characterised in the solid state by powder X-ray diffraction, N2 adsorption analysis, MAS NMR (13C, 29Si) and FTIR spectroscopy. The derivatised MCMs perform differently as catalysts in the liquid-phase oxidation of various olefins and alcohols with tert-butyl hydroperoxide. The highest alkene epoxidation activity was recorded for the catalysts with low metal loading, whereas the material containing oxo-bridged dimers had the highest activity for oxidation of alcohols. The recyclability of all the catalysts was tested: the catalytic activity of the derivatised materials tended to stabilize with ageing.

Journal Article↗
PubMed2004

Uniform micro-sized alpha- and beta-Si3N4 thin ribbons grown by a high-temperature thermal-decomposition/nitridation route.

Uniform micro-sized alpha- and beta-Si(3)N(4) thin ribbons have been achieved by a high-temperature thermal-decomposition/nitridation route. As-grown ribbons were characterized by using powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and cathodoluminescence. These alpha- and beta-Si(3)N(4) ribbons are structurally uniform micro-sized single crystals, and have a width of approximately 2-3 microns, a thickness of approximately 20-60 nm, and a length, that ranges from several hundreds of microns to the order of millimeters. A room-temperature cathodoluminescence spectrum recorded from these ribbons shows one intensive blue emission peak at approximately 433 nm. The growth for the new ribbon form of this material is believed to be dominated by a vapor-solid process.

Journal Article↗
PubMed2004

First preparation of nanocrystalline zinc silicate by chemical vapor synthesis using an organometallic single-source precursor.

A method is presented to prepare nanocrystalline alpha-Zn(2)SiO(4) with the smallest crystal size reported so far for this system. Our approach combines the advantages of organometallic single-source precursor routes with aerosol processing techniques. The chemical design of the precursor enables the preferential formation of pure zinc silicates. Since gas-phase synthesis reduces intermolecular processes, and keeps the particles small, zinc silicate was synthesized from the volatile organometallic precursor [[MeZnOSiMe(3)](4)], possessing a Zn-methyl- and O-silyl-substituted Zn(4)O(4)-heterocubane framework (cubane), under oxidizing conditions, using the chemical vapor synthesis (CVS) method. The products obtained under different process conditions and their structural evolution after sintering were investigated by using various analytical techniques (powder X-ray diffraction, transmission electron microscopy, EDX analysis, solid-state NMR, IR, Raman, and UV/Vis spectroscopy). The deposited aerosol obtained first (processing temperature 750 degrees C) was amorphous, and contained agglomerates with primary particles of 12 nm in size. These primary particles can be described by a [Zn-O-Si] phase without long-range order. The deposit obtained at 900 degrees C contained particles with embedded nanocrystallites (3-5 nm) of beta-Zn(2)SiO(4), Zn(1.7)SiO(4), and ZnO in an amorphous matrix. On further ageing, the as-deposited particles obtained at 900 degrees C form alpha-Zn(2)SiO(4) imbedded in amorphous SiO(2). The crystallite sizes and primary particle sizes in the formed alpha-Zn(2)SiO(4) were found to be below approximately 50 nm and mainly spherical in morphology. A gas-phase mechanism for the particle formation is proposed. In addition, the solid-state reactions of the same precursor were studied in detail to investigate the fundamental differences between a gas-phase and a solid-state synthesis route.

Organometallic Compounds↗
PubMed2004

A rationale for the large breathing of the porous aluminum terephthalate (MIL-53) upon hydration.

Aluminum 1,4-benzenedicarboxylate Al(OH)[O(2)C-C(6)H(4)-CO(2)]. [HO(2)C-C(6)H(4)-CO(2)H](0.70) or MIL-53 as (Al) has been hydrothermally synthesized by heating a mixture of aluminum nitrate, 1,4-benzenedicarboxylic acid, and water, for three days at 220 degrees C. Its 3 D framework is built up of infinite trans chains of corner-sharing AlO(4)(OH)(2) octahedra. The chains are interconnected by the 1,4-benzenedicarboxylate groups, creating 1 D rhombic-shaped tunnels. Disordered 1,4-benzenedicarboxylic acid molecules are trapped inside these tunnels. Their evacuation upon heating, between 275 and 420 degrees C, leads to a nanoporous open-framework (MIL-53 ht (Al) or Al(OH)[O(2)C-C(6)H(4)-CO(2)]) with empty pores of diameter 8.5 A. This solid exhibits a Langmuir surface area of 1590(1) m(2)g(-1) together with a remarkable thermal stability, since it starts to decompose only at 500 degrees C. At room temperature, the solid reversibly absorbs water in its tunnels, causing a very large breathing effect and shrinkage of the pores. Analysis of the hydration process by solid-state NMR ((1)H, (13)C, (27)Al) has clearly indicated that the trapped water molecules interact with the carboxylate groups through hydrogen bonds, but do not affect the hydroxyl species bridging the aluminum atoms. The hydrogen bonds between water and the oxygen atoms of the framework are responsible for the contraction of the rhombic channels. The structures of the three forms have been determined by means of powder X-ray diffraction analysis. Crystal data for MIL-53 as (Al) are as follows: orthorhombic system, Pnma (no. 62), a = 17.129(2), b = 6.628(1), c = 12.182(1) A; for MIL-53 ht (Al), orthorhombic system, Imma (no. 74), a = 6.608(1), b = 16.675(3), c = 12.813(2) A; for MIL-53 lt (Al), monoclinic system, Cc (no. 9), a = 19.513(2), b = 7.612(1), c = 6.576(1) A, beta = 104.24(1) degrees.

Journal Article↗
PubMed2004

Metal-complex assemblies constructed from the flexible hinge-like ligand H2bhnq: structural versatility and dynamic behavior in the solid state.

Novel metal-complex assemblies constructed from the flexible hinge-like ligand H(2)bhnq (H(2)bhnq=2,2'-bi(3-hydroxy-1,4-naphthoquinone)) have been synthesized. The X-ray crystal structures of these compounds reveal that four types of architectures are accessible by variation of the metal ions. In copper(II) compounds 1-3, the chelating bhnq(2-) ions bridge copper(II) centers to form one-dimensional zigzag chains. The chains of 1-3 are arranged by hydrogen-bonding interactions and stacking interactions to produce porous structures. Cobalt(II) and zinc(II) compounds 4 and 5 form one-dimensional helical chains. In 4 and 5, the crystal packing induces spontaneous resolution of the helical chains with chiral cavities formed perpendicular to the helices. Nickel(II) compounds 6 and 7 form cyclic tetramers. The fourth architecture, a dimer (compound 8), is obtained by the reaction of zinc(II) and bhnq(2-) in MeOH. In these compounds, changes of the dihedral angles and the metal-coordination mode of the bhnq(2-) ion induce the structural versatility. The assemblies of the zigzag chains of the copper(II) compounds exhibit reversible vapochromic behavior. UV/Vis, powder X-ray diffraction, EPR, and adsorption isotherm measurements indicate that this vapochromic behavior is based on the hinge-like flexibility of the bhnq(2-) ion.

Crystallography, X-Ray↗
PubMed2004

Benzene-templated hydrothermal synthesis of metal-organic frameworks with selective sorption properties.

In this paper, we report two metal-organic frameworks [Co3(ndc)3(bipyen)(1.5)]H2O (1) and [Co2(ndc)2bipyen)]C6H6.H2O (2) (bipyen=trans-1,2-bis(4-pyridyl)ethylene, H2ndc=2,6-naphthalenedicarboxylic acid). These compounds were both synthesized from identical hydrothermal reaction conditions except that benzene was added to the reaction for 2. Crystal structures show that the two compounds have triply interpenetrated three-dimensional frameworks and these frameworks have the same primary structure of a two-dimensional network of interconnected [Co2(O2CR)(4/2)] (R=naphthalene group) paddle-wheels and bridging bipyen ligands. Both compounds have guest water molecules and, in addition, 2 has guest benzene molecules. Structural transformations of the host accompanied guest removal, which can be monitored by powder X-ray diffraction. N2 adsorption data of 2 show that there are two different types of pores corresponding to the benzene and water pores. Upon exposure to vapors of several organic molecules, the heat-treated sample of 2 adsorbs benzene and cyclohexene, but does not adsorb toluene, (o-, m-, and p-)xylenes, cycloheptatriene, or cyclohexane.

Journal Article↗