Occluded Water Molecules Research Articles

Catena-Poly[2,2′,2′′-nitrilotris(ethanaminium) [tri-μ-oxido-tris[dioxidovanadate(V)]] monohydrate

The title compound, {(C6H21N4)[V3O9]·H2O}n, crystallizes as a salt with [trenH3]3+ cations [tren is tris­(2-amino­eth­yl)amine], and one-dimensional anionic {[VVO3]−}n (metavanadate) chains along the c-axis direction. Three crystallographically distinct VV sites and one occluded water mol­ecule are present for every [trenH3]3+ cation in the unit cell. The {[VVO3]−}n chains are composed of vertex-sharing [VO4] tetra­hedra and have a repeat unit of six tetra­hedra. Each tetra­hedron in the chain contains two terminal and two μ2-bridging oxide ligands. The [trenH3]3+ cations, {[VVO3]−}n anions and occluded water mol­ecules participate in an extensive three-dimensonal hydrogen-bonding network. The three terminal ammonium sites of the [trenH3]3+ cations each form strong N—H⋯O hydrogen bonds to terminal oxide ligands on the {[VVO3]−}n chain. Each occluded water mol­ecule also donates two O—H⋯O hydrogen bonds to the terminal oxide ligands.

The structural transformation of monoclinic [(R)-C5H14N2][Cu(SO4)2(H2O)4]·2H2O into orthorhombic [(R)-C5H14N2]2[Cu(H2O)6](SO4)3: crystal structures and thermal behavior

Single crystals of [(R)-C5H14N2][Cu(SO4)2(H2O)4]·2H2O (1) were grown through the slow evaporation of a solution containing H2SO4, (R)-C5H12N2 and CuSO4·5H2O. These crystals spontaneously transform to [(R)-C5H14N2]2[Cu(H2O)6](SO4)3 (2) over the course of four days at room temperature. The same single crystal on the same mounting was used for the determination of the structure of (1) and the unit cell determination of (2). A second single crystal of the transformed batch has served for the structural determination of (2). Compound 1 crystallizes in the noncentrosymmetric space group P21 (No. 4) and consists of trimeric [Cu(SO4)2(H2O)4]2− anions, [(R)-C5H14N2]2+ cations and occluded water molecules. Compound 2 crystallizes in P21212 (No. 18) and contains [Cu(H2O)6]2+ cations, [SO4]2− anions and occluded water molecules. The thermal decompositions of compounds 1 and 2 were studied by thermogravimetric analyses and temperature-dependent X-ray diffraction.

Thermodynamic Impact of Embedded Water Molecules in the Unfolding of Human CD2BP2-GYF Domain

GYF domains are small polyproline-recognition modules adopting a structural arrangement consisting of a single α-helix packed against a small β-sheet. Although most families of proline-rich recognition modules have been extensively characterized in terms of function, structure, or conformational flexibility, little is known about GYF domain functionality and folding. We have undertaken the thermodynamic characterization of the unfolding of CD2BP2-GYF domain by combining differential scanning calorimetry and circular dichroism under different pH conditions. The experimental data can be well-described in terms of a two-state equilibrium, although an unusually high heat capacity of the native state reflects a considerable conformational flexibility and dynamics of CD2BP2-GYF domain. In addition, the normalized thermodynamic parameters of unfolding (enthalpy, entropy and heat capacity) are roughly a factor of two greater than expected. In contrast, stability curves reveal an ordinary unfolding behavior of CD2BP2-GYF domain in terms of Gibbs energies, incurring thus unusually strong enthalpy-entropy compensation. This phenomenon, previously described as "thermodynamic homeostasis", has been associated in different examples to the contribution of occluded water (solvent) molecules into the protein structure. By means of CASTp server, we have found seven cavities/pockets scattered throughout of the CD2BP2-GYF structure, each able to harbor at least one water molecule. This structural feature provides rationalization for the atypical enthalpy values observed for CD2BP2-GYF because each water molecule is able to organize an extra amount of hydrogen bonds in the native state. In addition, these bound waters increase the vibrational entropy of the protein, which could also be responsible for an increase in protein flexibility and may thus fully explain the homeostatic behavior experimentally observed.

Synthesis and crystal structure of a new MOF-type indium pyromellitate (MIL-117) with infinite chains of unusual cis connection of octahedra InO 4(OH) 2

A new MOF-type indium pyromellitate (MIL-117) was hydrothermally synthesized at 483 K for 24 h. The structure of MIL-117 with structural formula In 6(OH) 6(btec) 3(H 4btec)·8–14H 2O (btec = 1,2,4,5-benzenetetracarboxylate), orthorhombic ( Pnmm) symmetry and unit cell parameters a = 8.2390(8), b = 22.251(2), c = 37.791(4) Å, V = 6928.2(11) Å 3 was solved from single-crystal diffraction data. The three-dimensional open framework structure consists of infinite chains of unusual cis sharing In-centered octahedra linked to each other through the pyromellitate ligands. The three distinct In(III) cations are coordinated to four oxygen atoms from carboxyl groups and two μ 2-hydroxyl groups in cis positions. The MIL-117 network delimits one-dimensional channels of 7.7 × 8.0 Å running along the a axis, where occluded water molecules are located. Although water species can be easily removed from the pore, no significant N 2 or CO 2 sorption was observed.

MIL-53(Fe): a good example to illustrate the power of powder diffraction in the field of MOFs

The field of “Metal-Organic Frameworks” (MOFs) has grown exponentially, giving rise to nanoporous materials with promising applications in gas storage, molecular separation or catalysis. Despite the use of solvothermal synthesis, some MOFs can be obtained only as polycrystalline samples and in those cases, powder diffraction is essential to characterize them. Herein, the nanoporous iron(III) terephthalate MIL-53(Fe), has been chosen to illustrate the power of powder diffraction in the field of MOFs. Its structure can be described as a one-dimensional channel system made up of trans-linked Fe octahedra, crosslinked by the bidentate dicarboxylate. Powder diffraction has been used to solve the structures of two MIL-53(Fe) samples obtained with and without fluorine. Differences between the two structural models concern the occluded water molecules which are ordered in absence of fluorine and disordered in the other case. MIL-53(Fe) shows reversible dehydration-hydration behaviour, via a metastable anhydrous phase, yielding an anhydrous phase with reduced porosity compared to its chromium analogue. Finally, sorption of organic molecules (benzene, benzoquinone, pyridine and 2,6-lutidine) in MIL-53(Fe), stud ied by using powder diffraction data in order to understand the nature of the host-guest interactions, is discussed.

Transformation of AlPO-53 to JDF-2: Reversible Dehydration of a Templated Aluminophosphate Studied by MAS NMR and Diffraction

We describe a detailed study of the aluminum phosphate AlPO-53 in both its as-made and calcined forms. In its as-made state, AlPO-53(A), the material is templated by methylammonium cations and contains occluded water molecules and also hydroxide ions that bridge pairs of aluminum atoms, increasing their coordination number to 5. Solid-state NMR experiments confirm the local environment of the aluminum and phosphorus atoms proposed in a previous structural model from powder X-ray diffraction. P-31 NMR shows the presence of four distinct resonances with an intensity ratio of 1: 1:2:2, consistent with the expected six crystallographic p Sites. Al-27 triple-quantum MAS NMR resolves five aluminum peaks, two with NMR parameters characteristic of four-coordinate Al and three of five-coordinate Al. One of these latter signals has a greater intensity than that of the others, consistent with the presence of two overlapping signals from two distinct crystallographic Al sites. First-principles calculations of NMR parameters provide a complete spectral assignment and confirm our interpretation of unresolved spectra. AlPO-53(A) is found to convert easily into a second crystalline phase on moderate heating (upon spinning in the NMR rotor for an extended period, for example), and variable-temperature powder X-ray experiments, together with TGA, suggest that this is a dehydration process yielding a second aluminophosphate, JDF-2. This is confirmed using both P-31 and Al-27 NMR, with the spectral assignment of JDF-2 supported by first-principles calculations. Calcination of AlPO-53(A) or of the dehydrated material, JDF-2, at 300 degrees C yields the microporous open-framework material AlPO-53(B), a tetrahedral network with three Al and three P sites, as confirmed by NMR and first-principles calculations. In addition to demonstrating the power of the combined use of NMR, first-principles calculations, and diffraction for detailed structural investigations, we show that the possibility of a reversible dehydration in as-made AlPO-53 and similar systems is an important consideration in structural studies and provides evidence that the published structural model for AlPO-53(A) may be incomplete.

Synthesis and structure of [C 6H 14N 2][(UO 2) 4(HPO 4) 2(PO 4) 2(H 2O)]·H 2O: An expanded open-framework amine-bearing uranyl phosphate

A new open-framework compound, [C 6H 14N 2][(UO 2) 4(HPO 4) 2(PO 4) 2(H 2O)]·H 2O, ( DUP-1) has been synthesized under mild hydrothermal conditions. The resulting structure consists of diprotonated DABCOH 2 2+ (C 6H 14N 2 2+) cations and occluded water molecules occupying the channels of a complex uranyl phosphate three-dimensional framework. The anionic lattice contains uranophane-like sheets connected by hydrated pentagonal bipyramidal UO 7 units. [C 6H 14N 2][(UO 2) 4(HPO 4) 2(PO 4) 2(H 2O)]·H 2O possesses five crystallographically unique U centers. U(VI) is present here in both six- and seven-coordinate environments. The DABCOH 2 2+ cations are held within the channels by hydrogen bonds to both two uranyl oxygen atoms and a μ 2-O atom. Crystallographic data (193 K, Mo Kα, λ=0.71073 Å): DUP-1, monoclinic, P2 1/ n, a=7.017(1) Å, b=21.966(4) Å, c=17.619(3) Å, β=90.198(3)°, Z=4, R(F)=4.76% for 382 parameters with 6615 reflections with I>2 σ( I).

Role of Water in the Ion Selectivity of Niobate-Based Octahedral Molecular Sieves

The role of occluded water in ion exchange selectivity is examined in a class of molecular sieves named Sandia Octahedral Molecular Sieves (SOMS: Na2Nb2-xMxO6-x(OH)x·H2O (i.e., M = Ti; 0 < x < 0.4)). SOMS exhibit a high selectivity for divalent cations only when the framework Nb(5+) are substituted by M(4+) atoms. Vibrational dynamics of the water molecules with varying charge balancing cations and M atoms are studied by inelastic neutron scattering (INS) measurements and 1H MAS NMR and correlated to density functional theory and molecular dynamics data. The experimental INS spectra were compared with those of ice Ih to characterize the changes induced by confinement on the occluded H2O and the resulting hydrogen-bonding network. Data indicates that, with increasing M(4+) content and divalent ion exchange, the trend of occluded water molecules is to change from extended rigid ice-like networks to restored bulk-like arrangements with increased solvation effects on the channel charge-balancing cations.

Cobalt-5-aminoisophthalate: [Co(AIPA)(OH2)2] n ·nH2O: a new one-dimensional rail-road polymer with occluded water molecules

A new structural form of cobalt-5-aminoisophthalate, [Co(AIPA)(OH2)2]n·nH2O (1) has been synthesized from the reaction of CoCl2·6H2O with 5-aminoisophthalic acid (AIPA-H2) in a 1:1 molar ratio at room temperature by layering aqueous solutions of the starting materials over a period of 2–3 weeks. [Co(AIPA)(OH2)2]n·nH2O (1) has been characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction studies. [Co(AIPA)(OH2)2]n·nH2O (1) crystallizes in triclinic space group P\(\bar{1}\) (a=7.549(2) A, b=8.833(2) A, c=9.080(2) A, α=62.23(3)°, β=75.09(3)°, γ=81.52(3)°). Compound 1 forms a rail-road like 1-D polymeric structure which is held together in the lattice by a variety hydrogen bonds aided by the presence of lattice water molecule. The Co2+ ion is in a severely distorted octahedral geometry with a CoO5N coordination environment.

Energetics of low-molecular-mass products of mechanical fracture of poly(methyl methacrylate)

It is experimentally revealed that monomer and water molecules released during the fracture of PMMA have a bimodal velocity distribution. The first distribution peak for the monomer corresponds to energetic (hot) MMA molecules (0.13–0.70 eV), and the second peak is attributed to MMA molecules bearing a low energy (0.016–0.060 eV). On the basis of the results of earlier theoretical studies of the mechanically induced polymer-chain scission, it was concluded that the energetic monomer molecules are produced immediately in the event of mechanical chain rupture and are nonthermal in nature. In the bimodal velocity distribution of occluded water molecules desorbed from a subsonic crack, the first and the second peaks are attributed to “hot” and “cold” molecules with translational temperatures of 605 ± 180 K and 53 ± 5 K, respectively. A possible mechanism of the mechanically induced desorption of occluded water is discussed. The mechanodesorption of water molecules is due to the portion of vibrational energy transferred to side methyl carboxylate groups that retain water molecules by the unloading-wave front traveling along the main chain from a macromolecule scission site. Along with hot water molecules, a considerable amount of hot free hydroxyls were detected. The mechanism of formation of the latter species is associated with the double-well structure of the hydrogen bond potential and similar to the mechanism of mechanodesorption of hot molecules of water.

Extended Networks, Porous Sheets, and Chiral Frameworks. Thorium Materials Containing Mixed Geometry Anions: Structures and Properties of Th(SeO3)(SeO4), Th(IO3)2(SeO4) (H2O)3×H2O, and Th(CrO4)(IO3)2.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Extended networks, porous sheets, and chiral frameworks. Thorium materials containing mixed geometry anions: Structures and properties of Th(SeO 3)(SeO 4), Th(IO 3) 2(SeO 4)(H 2O) 3·H 2O, and Th(CrO 4)(IO 3) 2

Three novel Th(IV) compounds containing heavy oxoanions, Th(SeO 3)(SeO 4) ( 1), Th(IO 3) 2(SeO 4)(H 2O) 3·H 2O ( 2), and Th(CrO 4)(IO 3) 2 ( 3), have been synthesized under mild hydrothermal conditions. Each of these three distinct structures contain trigonal pyramidal and tetrahedral oxoanions. Compound 1 adopts a three-dimensional structure formed from ThO 9 tricapped trigonal prisms, trigonal pyramidal selenite, SeO 3 2–, anions containing Se(IV), and tetrahedral selenate, SeO 4 2–, anions containing Se(VI). The structure of 2 contains two-dimensional porous sheets and occluded water molecules. The Th centers are found as isolated ThO 9 tricapped trigonal prisms and are bound by four trigonal pyramidal iodate anions, two tetrahedral selenate anions, and three coordinating water molecules. In the structure of 3, the Th(IV) cations are found as ThO 9 tricapped trigonal prisms. Each Th center is bound by six IO 3 1– anions and three CrO 4 2– anions forming a chiral three-dimensional structure. Second-harmonic generation of 532 nm light from 1064 nm radiation by a polycrystalline sample of 3 was observed. Crystallographic data (193 K, Mo Kα, λ = 0.7 1 0 7 3 ): 1; monoclinic, P2 1/ c; a = 7.0 3 5 1 ( 5 ) Å , b = 9.5 2 5 9 ( 7 ) Å , c = 9.0 2 6 6 ( 7 ) Å , β = 1 0 3.1 2 8 ( 1 ) , Z = 4 , R ( F ) = 2.4 7 % for 91 parameters with 1462 reflections with I > 2 σ ( I ) ; 2, monoclinic, P2 1/ n, a = 7.4 8 8 9 ( 9 ) Å , b = 8.0 0 2 ( 1 ) Å , c = 2 0.1 6 5 ( 3 ) Å , β = 1 0 0.1 4 2 ( 2 ) , Z = 4 , R ( F ) = 4.7 1 % for 158 parameters with 2934 reflections with I > 2 σ ( I ) ; 3, orthorhombic, P2 12 12 1, a = 7.3 6 7 2 ( 5 ) Å , b = 9.3 6 1 7 ( 6 ) Å , c = 1 1.9 2 0 1 ( 7 ) Å , Z = 4 , R ( F ) = 2.0 4 % for 129 parameters with 2035 reflections with I > 2 σ ( I ) .

Synthesis, structure and magnetic properties of a tin cobalt phosphate framework, SnCo 2(H 2O) 2(PO 4) 2 · H 2O

The hydrothermal inorganic reaction of cobalt chloride, tin oxalate and phosphoric acid yields a three-dimensional metal phosphate structure containing cobaltate layers. Hydrated tin phosphate chains connect the layers, defining unidimensional channels that contain occluded water molecules. Thermal and magnetic behaviour are also discussed. A cusp around 3.5 K and a negative Curie temperature of −35.9 K indicate antiferromagnetic exchange interactions between the Co(II) centers in the solid. The magnetic behavior follows the Curie–Weiss law in the 25–300 K range, with an effective magnetic moment of 3.18 μ B.

C5H14N2] [(MoO3)3(SO4)]×H2O: Sulfated α‐Molybdena Chains.

AbstractFor Abstract see ChemInform Abstract in Full Text.

C5H14N2][(MoO3)3(SO4)].H2O: sulfated alpha-molybdena chains.

Recent work in the preparation of organically templated metal sulfates under hydrothermal conditions has been extended to include the sulfation of alpha-molybdena through the synthesis of [C(5)H(14)N(2)][(MoO(3))(3)(SO(4))].H(2)O. Single crystals were grown under hydrothermal conditions from molybdenum oxide, water, sulfuric acid, and an enantiomerically pure (R)-2-methylpiperazine source and characterized using both single-crystal X-ray diffraction and infrared spectroscopy. One-dimensional [(MoO(3))(3)(SO(4))](n)(2n-) chains, based on a neutral alpha-molybdena backbone, are connected through an extensive hydrogen-bonding network containing [C(5)H(14)N(2)](2+) cations and occluded water molecules. The direction of the hydrogen bonding is primarily dictated by the nucleophilicity of the respective oxide ligands, as determined using bond valence sums.

Hydrothermal Syntheses, Structures, and Magnetic Properties of the U(IV) Fluorides (C5H14N2)2U2F12·5H2O and (NH4)7U6F31

The U(IV) fluorides (C5H14N2)2U2F12·5H2O (AU1-2) and (NH4)7U6F31 have been prepared from the reaction of UO3 with HF and homopiperazine (C5H12N2) at 180°C in aqueous media. AU1-2 contains dodecahedral UF8 units that share two edges to form 1∞[UF4F4/2] one-dimensional chains. The fluoride ligands form hydrogen bonds with the diprotonated homopiperazinium cations to yield channels running down the a axis that contain occluded water molecules. (NH4)7U6F31 is isostructural with Na7Zr6F31, forming a three-dimensional network consisting of edge- and corner-sharing UF8 square antiprisms that create cubooctahedral clusters and small intersecting channels. A disordered fluoride anion resides in the cubooctahedral cavities and the ammonium cations partially fill the channels. AU1-2 and (NH4)7U6F31 display similar magnetic behavior with μeff (300 K)=3.05 and 3.03 μB/U(IV) and θ=−97 and −126 K, respectively. Crystallographic data: AU1-2, monoclinic, space group P21/n, a=6.545(3) Å, b=19.90(1) Å, c=19.07(1) Å, β=98.89(4)°, Z=4, λ=0.71073 Å, R(F)=0.0395 for 293 parameters with 3282 reflections with I>2σ(I); (NH4)7U6F31, rhombohedral, space group R3, a=15.371(3) Å, c=10.791(3) Å, Z=3, λ=0.71073 Å, R(F)=0.0242 for 82 parameters with 841 reflections with I>2σ(I)

The First Fully Fluorinated Organically Templated Materials: Synthesis, Structures, and Physical Properties of [H3N(CH2)3NH3]U2F10·2H2O, [H3N(CH2)4NH3]U2F10·3H2O, [H3N(CH2)6NH3]U2F10·2H2O, and [HN(CH2CH2NH3)3]U5F24

A series of new layered uranium(IV) fluorides have been prepared under hydrothermal conditions from UO2, HF, and H3PO4 by using H2N(CH2)nNH2 (n = 3, 4, or 6), and N(CH2CH2NH2)3 as structure-directing agents. [H3N(CH2)3NH3]U2F10·2H2O (UFO-1), [H3N(CH2)4NH3]U2F10·3H2O (UFO-2), [H3N(CH2)6NH3]U2F10·2H2O (UFO-3), and [HN(CH2CH2NH3)3]U5F24 (UFO-4) have been characterized by single-crystal X-ray diffraction, thermogravimetric analysis, BET isotherms, and magnetic susceptibility measurements. UFO-1, 2, 3, and 4 contain negatively charged uranium fluoride (UF) layers constructed from linked UFn polyhedra separated by charge balancing organic cations and occluded water molecules. In UFO-1, 2, and 3, the layers are constructed from equivalent UF9 tricapped trigonal prisms that share three edges and two corners, whereas UFO-4 contains both UF8 bicapped trigonal prisms and UF9 tricapped trigonal prisms. We have demonstrated that the interlamellar organic cations in these materials can be ion-exchanged with a large var...

The First Organically Templated Layered Uranium(IV) Fluorides: (H3N(CH2)3NH3)U2F10⋅2 H2O, (H3N(CH2)4NH3)U2F10⋅3 H2O, and (H3N(CH2)6NH3)U2F10⋅2 H2O

A new series of layered organically templated uranium(IV) fluorides has been exclusively synthesized under hydrothermal conditions. The unprecedented materials contain [U2 F10 ]2- anionic layers that are separated by charge balancing cationic templates and occluded water molecules (see structure depicted). The templates can be fully ion-exchanged for a variety of metals (Na+ , K+ , and Co2+ ) at room temperature.

Dielectric Relaxations of Water Molecules Occluded in Polymeric Media: Some Hydrophobic Polymer Systems

The contributions of water occluded in polymeric media to dielectric relaxation were examined in detail on hydrophobic polymer specimens exposed to 18.7 torr humidity (78.6% relative humidity) at 25°C. The polymers examined were polyethylenes, oxidized polyethylenes, polystyrene, poly(styrene-co-acrylonitrile), poly(methyl methacrylate), and poly(vinyl acetate). In these polymers, except for the polyethylenes, the dielectric water relaxation peak usually appeared in a temperature range around 200 K (at 1 kHz) with an activation energy of about 40 to 50 kJ mol−1. The magnitude of dielectric dispersion due to water was calculated by the Onsager equation, assuming that occluded water molecules can rotate freely. The calculated values are about twice as large as the observed values for each system. This implies that the motion of water molecules is subject to certain hindrances from the polymeric media. In polyethylenes, especially in oxidized polyethylenes, the behavior of water molecules was markedly different from that in other polymers. Low- and medium-density polyethylenes absorbed virtually no water, while high-density polyethylene and oxidized polyethylenes absorbed a little. These polyethylenes exhibited two loss peaks at about 230 and 270K with the activation energies of about 120 and 316 kJ mol−1, respectively.