The crystal structure of jennite, Ca9Si6O18(OH)6·8H2O

The crystal structure of jennite is solved and refined in the space group P1?, by using single crystal X-ray diffraction data collected at the Elettra synchrotron radiation facility on a very thin crystal from Fuka, Japan. The triclinic refined unit cell is a=10.576(2) Å, b=7.265(2) Å, c=10.931(3) Å, α=101.30(1), β=96.98(1), γ=109.65(1)°. The structure of jennite is built up by three distinct modules: ribbons of edge-sharing calcium octahedra, silicate chains of wollastonite-type running along b, and additional calcium octahedra on inversion centres. The structural results indicate that the crystal chemical formula of jennite is Ca₉Si₆O₁₈(OH)₆·8H₂O, and that all the hydroxyl groups are bonded to three calcium cations; SiOH groups are not found. The structural disorder observed in jennite is explained on the basis of the OD theory, and a model for the structure of metajennite, the dehydration product of jennite, is proposed.     

Synthesis and characterization of a new chiral open-framework indium phosphite with intertwined host and guest helices

A new chiral open-framework indium phosphite In₃(HPO₃)₆(H₃DETA)·2H₂O 1 has been synthesized under hydrothermal conditions using achiral diethylenetriamine (DETA) as template and characterized by single crystal X-ray diffraction, powder X-ray diffraction, IR spectroscopy, TGA, ICP-AES and elemental analyses. Single crystal X-ray diffraction analysis reveals that the 3D inorganic framework is built up by alternation of InO₆ octahedra and HPO₃ pseudo-pyramids. Interestingly, the right-handed inorganic helical ribbons are presented in the 3D open-framework while fascinating hydrogen-bonded helices are self-assembled under hydrothermal conditions between organic template molecules and H₂O molecules. It is worth noting that the guest hydrogen-bonded helical chain and the host helical ribbon of inorganic framework show the same chirality and intertwine with each other along the b axis. Further understanding of the hydrogen bonds between guest molecules and inorganic framework demonstrates that the flexible DETA molecule may conduce to the formation of the chiral framework. Crystal data: In₃(HPO₃)₆·(H₃DETA)·2H₂O, Monoclinic, P2₁ (No. 4), a = 9.2713(19) Å, b = 14.453(3) Å, c = 9.996(2) Å, β = 116.16(3)°, V = 1202.2(4) ų, and Z = 2, Flack parameter: 0.0(4).     

LiBa1.5[B5O8(OH)3]: A new 1-D metal borate chain constructed from B5O9(OH)36 − cluster units

A new mixed metal borate LiBa_1.5[B₅O₈(OH)₃] (1) has been hydrothermally synthesized and structurally characterized by FT-IR spectroscopy, powder X-ray diffraction, single crystal X-ray diffraction, and thermogravimetric analysis, respectively. 1 crystallizes in the monoclinic system, space group C2/c, a = 11.2839(7) Å, b = 7.3974(4) Å, c = 20.7151(13) Å, β = 103.392(6)°, V = 1682.10(17) ų and Z = 8. The structure consists of infinite one-dimensional (1-D) borate chains constructed from B₅O₉(OH)₃^6 − cluster units. These BO chains are further linked by the Ba^2 + and Li⁺ cations to form a 3-D framework.     

The superstructure of C3S from synchrotron and neutron powder diffraction and its role in quantitative phase analyses

We have synthesised the room temperature MIII form of alite stabilised by doping with Mg and Al. The complex disordered superstructure of this tricalcium silicate [Ca₃SiO₅ (C₃S)] sample has been studied by a joint Rietveld refinement of ultra-high-resolution synchrotron X-ray powder diffraction data, medium-resolution neutron powder diffraction data and soft constraints of interatomic distances. Alite crystallises in a monoclinic cell with dimensions a=33.1078(6) Å, b=7.0355(1) Å, c=18.5211(4) Å, β=94.137(1)° and V=4302.9(2) ų. The final R factors were R_WP=8.76% and R_F(C₃S)=3.45% for the synchrotron data and R_WP=6.09% and R_F(C₃S)=5.10% for the neutron data. The reported superstructure is simpler than those previously reported, and it fits properly to a variety of Portland clinker and cement patterns. The Rietveld analyses of four clinkers with variable Mg contents have shown that the refinements are good. The Bogue approach gave quite poor results when compared to these state-of-the-art powder diffraction analyses. Bogue method slightly underestimates the C₃S+C₂S content, overestimates the C₃A fraction and underestimates the C₄AF content. Similar analyses of Portland cements with nine crystalline phases are shown to be feasible.     

Structural transition of Friedel's salt 3CaO·Al2O3·CaCl2·10H2O studied by synchrotron powder diffraction

The structural phase transition occurring in Friedel's salt, the chlorinated compound 3CaO·Al₂O₃·CaCl₂·10H₂O (AFm phase), was studied by synchrotron and standard X-ray powder diffraction. The compound transforms at 35 °C from a rhombohedral (rh) high-temperature (HT) phase [R−3c; a=5.744(2) Å, c=46.890(3) Å] to a monoclinic (m) low-temperature (LT) phase [C2/c; a=9.960(4) Å, b=5.7320(2) Å, c=16.268(7) Å, β=104.471(2)°]. The LT and HT phases were refined with the Rietveld method from synchrotron data recorded at 20 and 40 °C. Variations of the lattice parameters as a function of temperature are reported between 8 and 48 °C. The rh→m transition is characterized by a unit cell volume expansion of 1% and a movement of the interlayer species: a shift of 0.45 Å of the Cl⁻ anions along [010]_h and a shift of 0.25 Å of the water molecules along [210]_h of the hexagonal cell. The m phase distortion is due to an ordering of the hydrogen bonds between chloride anions and H-atoms of the water molecules.     

Carbonate and sulphate green rusts—Mechanisms of oxidation and reduction

The oxidation and reduction of carbonate, GR(CO₃), and sulphate, GR(SO₄), green rusts (GR) have been studied through electrochemical techniques, electrochemical quartz crystal microbalance (EQCM), FTIR, XRD and SEM. The used samples were made of thin films electrodeposited on gold substrate. The results from the present work, from our previous studies and from literature were compiled in order to establish a general scheme for the formation and transformation pathways involving carbonate or sulphate green rusts. Depending on experimental conditions, two routes of redox transformations occur. The first one corresponds to reaction via solution and leads to the formation of ferric products such as goethite or lepidocrocite (oxidation) or to the release of Fe^II ions into the solution (reduction) with soluble Fe^II-Fe^III complexes acting as intermediate species. The second way is solid-state reaction that involve conversion of lattice Fe²⁺ into Fe³⁺ and deprotonation of OH groups in octahedra sheets (solid-state oxidation) or conversion of lattice Fe³⁺ into Fe²⁺ and protonation of OH groups (solid-state reduction). The solid-state oxidation implies the complete transformation of GR(CO₃) or GR(SO₄) to ferric oxyhydroxycarbonate exGRc-Fe(III) or ferric oxyhydroxysulphate exGRs-Fe(III), for which the following formulas can be proposed, Fe^III₆(OH)_(12−2y)(O)_(2+y)(H₂O)_(y)(CO₃) or Fe^III₆(OH)_(12−2z)(O)_(2+z)(H₂O)_(6+z)(SO₄) with 0 ≤ y or z ≤ 2. The solid-state reduction gives ferrous hydroxycarbonate exGRc-Fe(II) or ferrous hydroxysulphate exGRs-Fe(II), which may have the following chemical formulas, [Fe^II₆(OH)₁₀(H₂O)₂]·[CO₃, 2H₂O] or [Fe^II₆(OH)₁₀(H₂O)₂]·[SO₄, 8H₂O].     

Synthesis,structure and electronic calculation of alkali metals borate Li2Na[B5O8(OH)2]

A new alkali metals borate complex, Li₂Na[B₅O₈(OH)₂], has been successfully synthesized by a facile hydrothermal method. Single-crystal X-ray diffraction analysis reveals that it crystallizes in orthorhombic space group Pbcn with a = 8.919(3) Å, b = 9.181(3) Å, c = 8.416(2) Å, Z = 4. The crystal structure is constructed of two dimensional (2D) [(B₅O₈)(OH)₂]_∞ layers, while stacking along b axis and then connected by Li⁺ and Na⁺ cations to extend to 3D framework Li₂Na[B₅O₈(OH)₂]. UV-vis-NIR spectrum shows that Li₂Na[B₅O₈(OH)₂] possesses a wide range of transparency and a UV cut-off edge below 190 nm which indicates that it may be applied in the deep ultraviolet region. The calculated band structures and the density of states indicate that Li₂Na[B₅O₈(OH)₂] is a direct band gap compound with a band gap of 5.68 eV. In addition, IR spectroscopy, thermal stability and theoretical calculations of Li₂Na[B₅O₈(OH)₂] are also reported in this work.     

A Novel Two-Dimensional Network Constructed by Bridged Salicylate and Pyrazine Ligands with Copper(II)

The coordination polymer, [Cu₂(sal)₂(pyz)(H₂O)₂] _n (H₂sal=salicylic acid, pyz=pyrazine), was synthesized and structurally characterized by X-ray crystallography. The empirical formula of the polymer is CuC₉NO₄H₈and the structural parameters are as follows: M _r=257.71, monoclinic, P2₁/c, Z=4, a=10.175(3) Å, b=7.352(4) Å, c=12.757(1) Å, =105.206(2)°, V=920.9(6) ų, D _c=1.859 g/cm³, (MoK)=23.62 cm^–1, F(000)=520 and the final R=0.048 for 2179 observable reflections. Each salicylate ligand connects the three copper centers to afford a novel 2-dimensional (2-D) network structure. The Cu^II-sal framework forms a rhombus type coordination framework. The pyz ligands fill the voids of the sheet and coordinate to the Cu site.     

Synthesis and characterization of the LDH hydrotalcite-pyroaurite solid-solution series

A layered double hydroxide (LDH) hydrotalcite-pyroaurite solid-solution series Mg₃(Al_xFe_1 − x)(CO₃)_0.5(OH)₈ with 1 − x = 0.0, 0.1……1.0 was prepared by co-precipitation at 23 ± 2 °C and pH = 11.40 ± 0.03. The compositions of the solids and the reaction solutions were determined using ICP-OES (Mg, Al, Fe, and Na) and TGA techniques (CO₃²⁻, OH⁻, and H₂O). Powder X-ray diffraction was employed for phase identification and determination of the unit cell parameters a_o and c_o from peak profile analysis. The parameter a_o = b_o was found to be a linear function of the composition. This dependency confirms Vegard's law and indicates the presence of a continuous solid-solution series in the hydrotalcite-pyroaurite system. TGA data show that the temperatures at which interlayer H₂O molecules and CO₃²⁻ anions are lost, and at which dehydroxylation of the layers occurs, all decrease with increasing mole fraction of iron within the hydroxide layers.Features of the Raman spectra also depend on the iron content. The absence of Raman bands for Fe-rich members (x_Fe > 0.5) is attributed to possible fluorescence phenomena.Based on chemical analysis of both the solids and the reaction solutions after synthesis, preliminary Gibbs free energies of formation have been estimated. Values of ΔG°_f(hydrotalcite) = − 3773.3 ± 51.4 kJ/mol and ΔG°_f(pyroaurite) = − 3294.5 ± 95.8 kJ/mol were found at 296.15 K. The formal uncertainties of these formations constants are very high. Derivation of more precise values would require carefully designed solubility experiments and improved analytical techniques.     

Hydrothermal synthesis of [Ba3Cl2][Sn3O4(OH)8], a compound with alternating ionic and covalent layers

[Ba₃Cl₂][Sn₃O₄(OH)₈] (1), is formed through hydrothermal synthesis in the BaCl₂/SnCl₄ system. 1 is orthorhombic, Pnma, a=7.836(2), b=18.350(4), c=10.258(2) Å, V=1475 ų and composed of alternating layers of covalent stannate and ionic barium chloride components. The ‘covalent’ layers consist of hydroxy stannate trimers [Sn₃O₄(OH)₈], connected through μ³-O to other units forming puckered 2-D sheets. These sheets are then intercalated by the barium and chloride ions, which have a complex set of ionic contacts.     

Interligand π,π-stacking interactions giving a bi-layered 2D framework in the crystal of poly-{(N4′-2,4′-bipyridine)-μ-(N,O,O′,O″-iminodiacetato)copper(II) hydrate}, {[Cu(IDA)(2,4′-bipy)]·H2O}n

The stoichiometric reaction of Cu₂CO₃(OH)₂, iminodiacetic acid [H₂IDA=HN(CH₂CO₂H)₂)] and 2,4^′-bipyridine (2,4^′-bipy) in water yields crystalline samples of {[Cu(IDA)(2,4^′-bipy)]·H₂O}_n. The compound was studied by thermal, spectral (FT-IR and reflectance), magnetic (ESR and susceptibility) and X-ray diffraction methods. The structure was solved and refined to a final R₁=0.035. The Cu(II) atom exhibits a type 4 + 1 coordination and 2,4^′-bipy ligand links the metal by its N4-donor. IDA exhibits a mer-tridentate chelating role and uses a syn-anti-bridging carboxylato group to give polymeric chains extending parallel to the c axis, leaving all 2,4^′-bipy ligands towards the same side. Water molecule reinforces the chain stability forming H-bonds with two O(carboxyl) acceptors from adjacent complex units. Both pyridyl rings of 2,4^′-bipy are nearly coplanar (1.0(2)°). Adjacent 2,4^′-bipy ligands of the same complex chain define an open dihedral angle (69°). 2,4^′-bipy ligands belonging to symmetry related chains stack both pyridyl rings at 3.40 Å, thus forming a 2D framework with IDA ligands lying towards both external faces and N-heterocyclic ligands inside. In the crystal N(IDA)-H⋯O(IDA) hydrogen bonds connect up and down adjacent 2D frameworks in a 3D network.     

The crystal structure of poly(2,6-naphthalenebenzobisthiazole)

The crystal structure of poly(2,6-naphthalenebenzobisthiazole) (Naph-2,6-PBT) was studied using X-ray and molecular modeling methods. The X-ray pattern of the annealed Naph-2,6-PBT fiber showed several Bragg reflections as well as streaks along the layer lines indicating that the registry between adjacent chains exists in the crystal with a great deal of axial disorder. Disordered structure in the crystal was fitted into the triclinic unit cell with the unit cell parameters of a=6.78 Å, b=3.46 Å, c=14.61 Å, α=88.0°, β=114.7°, and γ=94.8° with space group. The calculated density, 1.68 g/cm³ was comparable with the observed density, 1.56 g/cm³. The Δc/c (staggering ratio) representing the registry between the adjacent chains in the ac plane was −0.19, which is in good agreement with the energy calculation although another local energy minimum was found at Δc/c=0.31. The disordered structure in Naph-2,6-PBT was probably due to the discrete axial shift between Δc/c=0.31 and −0.19 in the ac plane. The LALS refinement showed that the naphthalene group was rotated by 9 (±3)° from the ac plane on the projected structure along the chain axis with a torsion angle between the naphthalene and benzobisthiazole rings of 23°.     

Crystal structure of low magnesium-content alite: Application to Rietveld quantitative phase analysis

Five members of tricalcium silicate solid solution, Ca_{3 − x − y}Mg_xAl_y(Si_1 − yAl_y)O₅, have been prepared. T_1, T₃ and M₃ forms have been identified by X-ray powder diffraction, but pure M₁ form was not stabilized. The crystal structure of a sample nominally Ca_2.96Mg_0.03Al_0.01(Si_0.99Al_0.01)O₅ has been studied by a joint Rietveld refinement using strictly monochromatic laboratory X-ray and neutron powder diffraction data, with soft constraints of interatomic distances. The crystal structure of this alite is a T₃ form with a triclinic cell, space group P 1?1­, of dimensions a = 11.6389(2) Å, b = 14.1716(3) Å, c = 13.6434(3) Å, α = 104.982(2)°, β = 94.622(1)°, γ = 90.107(2)° and V/Z = 120.346(6) ų. Laboratory and commercial clinkers were studied by synchrotron X-ray powder diffraction and the Rietveld method. The reported T₃ structure for alite fits properly a variety of laboratory Portland clinkers with low magnesium contents. The alite refined volume(s) (V/Z) is useful to predict the magnesium oxide content of a clinker and the alite-type. Thus, a refined V/Z value between 121.0 and 120.3 Å³ should contain up to ~ 1.0 wt.% of MgO, being T₃ type. If refined C₃S V/Z is smaller than ~ 119.8 Å³ the clinker may contain more than ~ 2.1 wt.% of MgO with alite as M₃. For intermediate magnesium (and sulfur) contents, alites phase coexistence may be detected by using strictly monochromatic laboratory or synchrotron X-ray powder diffraction. However, the application of these results to commercial materials has to be taken cautiously due to the influence of other foreign ions in volume and alite-type.     

Preparation, characterization and bifunctional electrocatalysis of an inorganic-organic complex with a vanadium-substituted polyoxometalate

An inorganic-organic complex with a vanadium-substituted polyoxometalate 1, formulated as [Cu(phen)₂]₂PVW₁₁O₄₀ was hydrothermally synthesized. Complex 1 crystallizes in the monoclinic P2(1)/c space group with a = 25.9932(12) Å, b = 11.9889(6) Å, c = 23.2672(11) Å, β = 113.6750(10)°, V = 6640.5(6) Å³, R = 0.0312, and Z = 4. Complex 1 is constructed from a Keggin-type anion PVW₁₁O₄₀⁴⁻ coordinated to two [Cu(phen)₂]²⁺ units. One [Cu(phen)₂]²⁺ unit is coordinated to a terminal oxygen and the other [Cu(phen)₂]²⁺ unit is coordinated to a bridging oxygen of the polyoxoanion. Redox activities for both the tungsten and vanadium centers have been observed using cyclic voltammetry performed on 1-bulk modified carbon paste electrode (CPE). It was found that 1 presents good electrocatalytic activities not only for the reduction of IO₃⁻, NO₂⁻, and H₂O₂ but also the oxidation of l-cysteine. Complex 1 also shows intense luminescent properties arising from ligand-to-copper charge transfer and oxygen-to-vanadium charge transfer at room temperature in the solid state.     

A unique 3D Co(II)-MOF based on [Co6(μ3-OH)4]8 +n chains: Synthesis,crystal structure,and magnetic property

A novel metal-organic framework, [Co₆(μ₃-OH)₄(ndc)₄(bip)₂(H₂O)₂]_n (1)[H₂ ndc = 1,4-naphthalenedicarboxylic acid, bip = 1,5-bis(imidazole-1-yl)pentane], constructed from unique [Co₆(μ₃-OH)₄]^8 +_n chains containing alternate [Co₄(OH)₂]^6 + and [Co₂(OH)₂]^2 + subunits, was reported, which has a new (3,3,8,12)-connected or 12-connented fcu/cubic network and shows weak antiferromagnetic interaction between the adjacent Co(II) ions mediated through the carboxylate and hydroxyl groups.     

Synthesis and electrochemical characterization of orthorhombic LiMnO2 material

Well-defined orthorhombic LiMnO₂ was synthesized using LiOH and γ-MnOOH starting materials at 1000 °C in an argon flow by quenching process. X-ray diffraction (XRD) revealed that the compound showed an orthorhombic phase of a space group with Pmnm (a=2.806 Å, b=5.750 Å, and c=4.593 Å). The prepared compound was composed of particles of about 5-15 μm diameter with a bar-shape and small spherical one of about 1-2 μm. It showed very small initial discharge capacity of about 34 mA h g⁻¹ in the (3+4) V region at room temperature. However, after 12 h grinding, the LiMnO₂ delivered 201 mA h g⁻¹ in the first cycle and still delivered 200 mA h g⁻¹ after 50 cycles at room temperature. We found that the initial discharge capacity of LiMnO₂ agreed well with its specific surface area by Brunauer, Emmett and Teller (BET) analysis. Especially, the grinding treatment played an important role to activate the lithium insertion-extraction into the LiMnO₂ layer in the 3 V region.     

Structures and photoluminescence of coordination polymers assembled from bifunctional ligand containing both tetrazole and imidazole groups

Three new coordination polymers, namely, {[Cu₂(IPT)(SO₄)(OH)(H₂O)]·H₂O}_n (HIPT = 5-(4-(1H-imidazol-1-yl)phenyl)- 1H-tetrazolate, 1), {[Cd₂(IPT)(NPA)(OH)]·H₂O}_n (H₂NPA = 5-nitroisophthalic acid, 2), and {[Zn₂(IPT)(IDC)(H₂O)]·3H₂O}_n (H₃IDC = 1H-imidazole-4,5-dicarboxylic acid, 3), were assembled from a bifunctional organic ligand containing both tetrazole and imidazole groups with/without the aid of carboxylate coligands. Compound 1 possesses 2D structure built by 1D [Cu₂(IPT)(SO₄)(OH)]_n secondary building blocks and IPT⁻ linkers. The 2D networks are linked into 3D supramolecular framework via water chains in helical conformation. Compound 2 displays 3D pillar-layer framework with 2D layers based on tetranuclear Cd(II) SBUs and NPA^2 − pillars. Compound 3 exhibits a 3D framework constructed from the interconnection of 1D [Zn-IDC]_n chains and binuclear Zn₂(IPT)₂ rings. The thermal stabilities of porous compound 3 and luminescent properties of compounds 2 and 3 have also been studied in detail. They exhibit intense solid-state fluorescent emissions at room temperature.     

The structures of poly(oxyethylene)s having sulfone groups in the side chains

The structures of (OCH₂CHR) with R=CH₂S(CH₂)₆SO₂(CH₂)_MH (ATP-M; M=5,7,9) or R=CH₂SO₂(CH₂)₆SO₂(CH₂)_MH (ASP-M; M=5,7,9) were studied using X-ray diffraction and differential scanning calorimetry. The X-ray patterns of all ATPs and ASPs studied show a series of ordered reflections in the small angle region and a sharp wide angle reflection at d=∼4.4 Å, characteristic of a smectic phase. The smectic layer thickness corresponds to twice the most extended side chain length and linearly increases as the side chain length increases with a slope of ∼2.3 Å per methylene spacer. This indicates that all ASPs and ATPs studied have a double layer structure with side chains normal to the main chain and probably an all-trans conformation of the side chains. The correlation lengths measured from the wide angle reflections are in the range of 80±10 Å for all the polymers except for ASP-5 (∼40 Å). These values indicate that quasi-long-range order exists in the smectic layers whose structures can be defined as smectic B (S_B). The d-spacing of the wide angle reflection, 4.4 Å, suggests that paraffinic side chain crystallization does not occur and that the smectic mesophase develops through dipole-dipole interactions of sulfone groups in the side chains. During heating, ATP-5 shows recrystallization after the first melting. The structure produced during recrystallization has a similar smectic structure but with more dense packing between side chains than before the first melting. In the case of ASP-9, a smectic to smectic transition was observed at ∼110°C prior to the isotropic temperature at ∼150°C. Both the correlation length (from the wide angle reflection) and the layer thickness decreased from ∼80 to ∼30 Å and from 46 to 40 Å at this transition, respectively, indicating that the order in the smectic layers is lost and the S_B structure has become a less ordered S_A structure at this transition.     

The hydrothermal synthesis and structure of a one-dimensional Fe(II)molybdophosphate

A new one-dimensional Fe(II)molybdophosphate of the formula, [(C₁₀H₈N₂)H₂]₂[Fe₄^(II)Mo₁₂^(V)(HPO₄)₆(PO₄)₂(H₂O)₈(OH)₆O₂₄]·8H₂O, (1), has been synthesized by employing hydrothermal methods and characterized by single crystal X-ray diffraction. The structure consists of a network of MO₆ (M = Fe, Mo) octahedra and (H)PO₄ tetrahedra linked through their vertices. The connectivity between the polyhedral units gives rise to one-dimensional chains with eight-membered apertures. The hydrogen bonded interactions between the chains form pseudo two-dimensional layers. Extensive hydrogen bonding also exists between the amine molecule, 4,4^′-bipyridine, water molecule and framework oxygen atoms. Crystal data for 1: monoclinic, space group = P2₁ (no. 4), a=12.549(3) (Å), b=23.496(5) (Å), c=14.551(3) (Å), β=114.87(3)°, , and Z=2.