Non-equivalent Water Molecules Research Articles

Catena-Poly[[[diaquabis[1,2-bis(pyridin-4-yl)diazene]copper(II)]-μ-1,2-bis(pyridin-4-yl)diazene] bis(perchlorate)

In the title compound, {[Cu(C10H8N4)3(H2O)2](ClO4)2}n, the coordination environment of the cationic CuII atom is distorted octa­hedral, formed by pairs of symmetry-equivalent 1,2-bis­(pyridin-4-yl)diazene ligands, bridging 1,2-bis­(pyridin-4-yl)diazene ligands and two non-equivalent water mol­ecules. The 1,2-bis­(pyridin-4-yl)diazene mol­ecules form polymeric chains parallel to [-101] via azo bonds which are situated about inversion centres. Since the CuII atom is situated on a twofold rotation axis, the monomeric unit has point symmetry 2. The perchlorate anions are disordered in a 0.536 (9):0.464 (9) ratio and are acceptors of water H atoms in medium–strong O—H⋯O hydrogen bonds with graph set R 4 4(12). The water mol­ecules, which are coordinated to the CuII atom and are hydrogen-bonded to the perchlorate anions, form columns parallel to [010]. A π–π inter­action [centroid–centroid distance = 3.913 (2) Å] occurs between pyridine rings, and weak C—H⋯O inter­actions also occur.

Is the mineral borickyite (Ca,Mg)(Fe3+,Al)4(PO4,SO4,CO3)(OH)8·3–7.5H2O the same as delvauxite CaFe43+(PO4,SO4)2(OH)8·4–6H2O?

The two minerals borickyite and delvauxite CaFe43+(PO4,SO4)2(OH)8·4–6H2O have the same formula. Are the minerals identical or different?The minerals borickyite and delvauxite have been characterised by Raman spectroscopy. The minerals are related to the minerals diadochite and destinezite. Both minerals are amorphous. Delvauxite appears to vary in crystallinity from amorphous to semi-crystalline. The minerals are often X-ray non-diffracting. The minerals are found in soils and may be described as ‘colloidal’ minerals. Vibrational spectroscopy enables an assessment of the molecular structure of borickyite and delvauxite. Bands are assigned to phosphate and sulphate stretching and bending modes. Multiple water bending and stretching modes imply that non-equivalent water molecules in the structure exist with different hydrogen bond strengths. The two minerals show differing spectra and must be considered as different minerals.

A vibrational spectroscopic study of the mixed anion mineral sanjuanite Al 2(PO 4)(SO 4)(OH)·9H 2O

The mineral sanjuanite Al 2(PO 4)(SO 4)(OH)·9H 2O has been characterised by Raman spectroscopy complimented by infrared spectroscopy. The mineral is characterised by an intense Raman band at 984 cm −1, assigned to the (PO 4) 3− ν 1 symmetric stretching mode. A shoulder band at 1037 cm −1 is attributed to the (SO 4) 2− ν 1 symmetric stretching mode. Two Raman bands observed at 1102 and 1148 cm −1 are assigned to (PO 4) 3− and (SO 4) 2− ν 3 antisymmetric stretching modes. Multiple bands provide evidence for the reduction in symmetry of both anions. This concept is supported by the multiple sulphate and phosphate bending modes. Raman spectroscopy shows that there are more than one non-equivalent water molecules in the sanjuanite structure. There is evidence that structural disorder exists, shown by the complex set of overlapping bands in the Raman and infrared spectra. At least two types of water are identified with different hydrogen bond strengths. The involvement of water in the sanjuanite structure is essential for the mineral stability.

A Raman and infrared spectroscopic study of the mineral delvauxite CaFe 43+(PO 4,SO 4) 2(OH) 8·4–6H 2O—A ‘colloidal’ mineral

The mineral delvauxite CaFe 4 3+(PO 4,SO 4) 2(OH) 8·4–6H 2O has been characterised by Raman spectroscopy and infrared spectroscopy. The mineral is associated with the minerals diadochite and destinezite. Delvauxite appears to vary in crystallinity from amorphous to semi-crystalline. The mineral is often X-ray non-diffracting. The minerals are found in soils and may be described as ‘colloidal’ minerals. Vibrational spectroscopy enables determination of the molecular structure of delvauxite. Bands are assigned to phosphate and sulphate stretching and bending modes. Two symmetric stretching modes for both the phosphate and sulphate symmetric stretching modes support the concept of non-equivalent phosphate and sulphate units in the mineral structure. Multiple water bending and stretching modes imply that non-equivalent water molecules in the structure exist with different hydrogen bond strengths.

Crystal structures and spectroscopic properties of ester amide and diamide of squaric acid with prolinamide

We report the synthesis, spectroscopic and structural elucidation of two prolinamide derivatives of squaric acid, i.e. prolinamide ester amide of squaric acid ethyl ester ( 1) and prolinamide diamide of squaric acid dihydrate ( 2). Both compounds crystallize in non-centrosymmetric space groups, monoclinic P2 1 ( 1) and orthorhombic P2 12 12 1 ( 2), respectively. For first time in the literature the crystal structure of homodiamide of amino acid amide of squaric acid is reported. The data for heterodiamides is also absent. Supramolecular zig-zag chains by hydrogen bonds of H 2N–C O⋯HNH (3.020 Å) and HNH⋯O C (Sq) (2.972 Å) types with the participation of amide and squaric acid (Sq) fragments, –C O–NH 2 and O C (Sq) are refined in ( 1). A helix supramolecular structure is formed in ( 2) by moderate intermolecular HNH⋯O C(NH 2) hydrogen bond with length of 2.947 Å. The two crystallographical non-equivalent water molecules stabilized the helix by interactions of types HOH⋯O C (Sq) (2.917 Å), HOH⋯O C(NH 2) (2.899 Å), H 2O⋯NH 2(C O) (2.972 Å), respectively. Optical and magnetic properties are investigated with a view to explain the correlation structure-properties of the newly synthesized molecules.

Raman spectroscopic study of the uranyl carbonate mineral zellerite

AbstractRaman and infrared spectra of the uranyl mineral zellerite, Ca[(UO2)(CO3)2(H2O)2]·3H2O, were measured and tentatively interpreted. UO bond in uranyl and OH···O hydrogen bonds were calculated from the vibrational spectra. The presence of structurally nonequivalent water molecules in the crystal structure of zellerite was inferred. A proposed chemical formula of zellerite is supported. Raman bands at 3514, 3375 and 2945 cm−1and broad infrared bands at 3513, 3396 and 3326 cm−1 are related to the ν OH stretching vibrations of hydrogen‐bonded water molecules. Observed wavenumbers of these vibrations prove that in fact hydrogen bonds participate in the crystal structure of zellerite. The presence of two bands at 1618 and 1681 cm−1 proves structurally distinct and nonequivalent water molecules in the crystal structure of zellerite. Copyright © 2008 John Wiley & Sons, Ltd.

Crystal structure and MAS-NMR study of rehydrated UiO-7

Abstract The framework of rehydrated UiO-7 has the ZON type of topology. The crystal structure is described on the basis of high resolution, synchrotron powder X-ray diffraction data. The chemical composition of the unit cell is Al 32 P 32 O 128 ·62H 2 O. Its dimensions are a =14.4930(2), b =14.8731(2) and c =17.5738(3) A; space group Pbca . Of the four non-equivalent Al atoms, two have normal tetrahedral coordination, whereas one obtains five-coordination and one achieves octahedral coordination on additional bonding to three non-equivalent water molecules. Six more water molecules are located in the channels and are interconnected via hydrogen bonds. These features were confirmed by solid-state 27 Al MAS NMR data. Site assignment of 31 P signals is discussed on the basis of POAl angles and Al-coordination.

The state of water in tricalcium phosphate obtained by precipitation from a solution

Tricalcium phosphate with the ratio Ca : P = 1.5 and the empirical composition corresponding to the formula Ca3(PO4)2 · 3H2O is synthesized by precipitation from a solution. It constitutes hydroxyapatite with defective structure and is the extreme member of the solid solution series between tricalcium phosphate Ca3(PO4)2 and hydroxyapatite Ca10(PO4)6(OH)2. The state of water in the product structure and the dehydration specifics are considered. The presence of crystallographically nonequivalent water molecules is identified, which determines the stepwise course of dehydration.

Vibrational and Thermal Evidence of Coordinated Water and Carboxylate Groups in Crystalline Calcium Malonate Dihydrate

Revision of the crystal structure of calcium malonate dihydrate, [Ca(mal)(H2O)2], has shown that it belongs to the monoclinic system, space groupC2/m, witha=13.857(6),b=6.8072(8),c=6.806(5) Å,β=106.31(7)°,Z=4, andV=616.2(5) Å3. This is in agreement with one of the previous structural determinations, and nonequivalent water molecules and chelating and bridging carboxylate groups in the crystal lattice are evidenced. The infrared and Raman spectra were recorded and discussed in relation to the structural properties. Librational modes of water have been clearly identified and an assignment for all the internal modes is proposed. The thermal dehydration and decomposition processes were investigated using TG/DTA measurements. The structural model is consistent with the vibrational behavior and the two different temperatures observed in the dehydration process.

INTERMEDIATES IN THE THERMAL DECOMPOSITION OF NORMAL COPPER(II), NICKEL(II) AND COBALT(II) SELENITE DIHYDRATES

Abstract Thermal decomposition of normal transition metal selenite dihydrates, MSeO2.2H2O; M [dbnd] Cu(II), Ni(II), Co(II) was traced by TGA/DTA measurements from 50–700°C. The thermal products were obtained by heating the selenites in an air-oven to different temperatures, as determined from TGA/DTA curves, where different coloured products are obtained. The structures of the start selenites and the thermal intermediates were determined by chemical analyses and FT-IR spectral measurements. The start selenites proved to be equilibrium mixtures of the selenite, hydrogenselenite and/or pyroselenite anions. Gradual changes occurred in the FT-IR spectra of the nickel and cobalt selenites on thermal treatment till 225°C where, due to water loss, merely selenite anions are observed. In the case of the copper selenite, the selenito mixture persists till 250°C and the only change observed in the final product is the disappearance of one of the structurally non-equivalent water molecules present in the start selen...

Electron spin resonance and electron spin echo modulation studies of copper(II) ions in the aluminosilicate chabazite: a comparison of copper(II) cation location and adsorbate interaction with isostructural silicoaluminophosphate-34

This study focuses on Cu(II) ions exchanged in the aluminosilicate zeolite chabazite. The various Cu(II) species formed after dehydration, rehydration, and exposure to adsorbates are characterized by electron spin resonance and electron spin echo modulation spectroscopies. These results are interpreted in terms of Cu(II) ion location and adsorbate interaction. The results of this study are compared to the results found earlier for SAPO-34, chabazite`s structural analog from the silicoaluminophosphate group. In a hydrated sample of chabazite the Cu(II) ions are found to be in a near octahedral environment coordinated to three nonequivalent water molecules and three framework oxygens. The most probable location of the Cu(II) ion in a hydrated sample is above the plane of the six-membered ring slightly displaced into the ellipsoidal cavity. A somewhat similar location and coordination is found for Cu(II) ions in H-SAPO-34. A feature common to both CuH-chabazite and CuH-SAPO-34 is the generation of two distinct Cu(II) species upon dehydration. It is found that Cu(II) cations in chabazite interact with the various adsorbate molecules in a similar manner as Cu(II) cation in H-chabazite and three molecules of ethanol and three propanol molecules. Only the Cu(II) ions located in the hexagonal rings after dehydration were foundmore » to complex with ethylene. The differences observed in the interaction of the Cu(II) in with water, propanol, and ehtylene between SAPO-34 and chabazite can be related to the differing cation densities of these two materials. 32 refs., 7 figs., 21 tabs.« less

Synthesis and properties of beryllium iodates—III. Synthesis, IR spectra and X-ray diffraction analysis of Be(IO 3) 2·2HIO 3·6H 2O

The compound Be(IO 3) 2·2HIO 3·6H 2O has been synthesized and identified by quantitative analysis, IR spectra and X-ray diffraction analysis. On the basis of the absorption bands in the IR spectra of the compound and its partially deuterated analogue the basic structural units making up the compound were shown to be Be(H 2O) 4(IO 3) 2· 2HIO 3·2H 2O, as well as the existence of two kinds of non-equivalent water molecules.

Some new data concerning the interface chemistry of dehydration reactions

Temperature dependence of the rate of reaction interface advance in reactions of thermal dehydration of single crystals was studied by means of quartz crystal microbalance along various crystallographic directions. Both kinetic and microscopic data show different interface chemistry for crystalline hydrates with equivalent and non-equivalent water molecules.

Structural investigations on Sr(NO 2) 2 · X2O ( X = H, D): a vibrational analysis

The infrared absorption (at 300 K and 93 K) and the laser Raman spectra (at 300 K) of polycrystalline Sr(NO 2) 2 · H 2O and its deuterated analogue in the range 30–4000 cm −1 have been studied. The salt is shown to contain two non-equivalent water molecules and at least three non-equivalent nitrite groups per unit cell. The average bond enthalpies for the two kinds of water molecules are estimated to be 16.5 and 11.6 kJ mol −1. The spectra exhibit exceptionally low intensity of the bending fundamentals of H 2O molecules. A cyclic structure formed by H 2O(I) and H 2O(II) is proposed to explain this behaviour.

OD Stretching Vibrations in Deuterated Potassium Ferrocyanide Trihydrate

AbstractDeuterated and isotopically dilute single crystals of K4Fe(CN)6. 3 D2O are investigated using low temperature Raman spectra. The work involves an attempt to asses the origin of the numerious OD modes using the isotope dilution technique. An estimate of the magnitude of the intra‐ and intermolecular interactions in formation of OD stretchings is made from available experimental data. Three crystallographically nonequivalent water molecules with different extent of vibrational distortion are established in the ferroelectric phase of the crystal.

The Crystal Structures of Tin(II) Chloride Dihydrate in High- and Low-Temperature Phases as Studied by Neutron and X-Ray Diffractions

Abstract The neutron-diffraction results for deuterated single crystals have shown definitely that the phase transition is ascribable to the ordering of the hydrogen atoms. The ordered arrangement below the transition temperature (Tt=234 K) agrees well with the NMR results. No doubling of the unit cell or loss of the center of symmetry can be detected. In the disordered phase above Tt, four deuterons of two non-equivalent water molecules are distributed into seven sites. The occupancy factors of the individual sites have been refined by least-squares methods under different constraints. Bernal and Fowler’s ice rule is obeyed in the H-bonded water layers, and the water molecules of crystallization scarcely dissociate at all. The crystal structure has been redetermined by the X-ray diffraction method at 209 and 223 K, using an SnCl2·2H2O single crystal. No distinct change in the structure of non-hydrogen atoms has been disclosed on passing through the transition point (Tt=218 K). However, in the close vicinity of Tt, the a and c lattice parameters and the three H-bonded O···O distances steeply change in association with the ordering of the hydrogen atoms.

Hydrogen bond studies. CXX. An X-ray determination of the crystal structure of LiNO3.3H2O

For pt.CXIX see Z. Naturforsch. a, vol.32, p.134 (1977). The crystal structure of lithium nitrate trihydrate, LiNO 3.3H 2O, has been determined by X-ray diffraction at 295K. The crystal is orthorhombic, space group Cmcm, a=6.8018 (4), b=12.7132 (9), c=5.9990 (4) Aring, V=518.75 Aring 3, Z=4. The nitrate ions, Li + ions and one of the two crystallographically non-equivalent water molecules lie in a mirror plane and are bonded to atoms in adjacent planes through the second water molecule. The Li + ion is octahedrally surrounded by six O atoms, four belonging to water molecules and two to nitrate ions. The two non-equivalent water molecules are present in the structure in distinctly different bonding situations. One is bonded to two Li + ions and is the donor of two hydrogen bonds. The other is involved in six hydrogen bonds: the O atom accepts two hydrogen bonds, and both protons are involved in bifurcated hydrogen bonds.

ORDERED AND DISORDERED HYDROGEN BONDS IN TIN(II) CHLORIDE DIHYDRATE FROM SINGLE CRYSTAL NEUTRON DIFFRACTION

Abstract Single crystal neutron diffraction shows that the deuteron arrangements in SnCl2·2D2O are ordered and disordered, respectively, below and above Ttr. In the high temperature phase four deuterons of two non-equivalent water molecules distribute among seven sites with individual occupancy factors.

Proton Magnetic Resonance in Cupric Formate Tetrahydrate, Cu(HCO2)2·4H2O

Abstract The proton magnetic resonance spectra of Cu(HCO2)2·4H2O have been investigated over the range 110° to 315°K, using both single crystal and powdered samples. The water molecules are effectively rigid below the phase transition temperature, 237°K, and the most probable positions of the protons of the two non-equivalent water molecules are postulated on the basis of Pake’s method. The narrowing of the absorption line occurs above 237°K; this implies the gradual onset of a certain motion of both kinds of water molecules. The absorption spectra in the higher temperature range of 300∼315°K indicate that the reorientation of the water molecules takes place almost exclusively about one axis.

THE VIBRATIONAL SPECTRA OF ROCHELLE SALT

This paper deals primarily with the vibrational bands of crystalline water molecules in Rochelle Salt. The four bands observed in the region 3200-3600 cm-1 are attributed respectively to the four nonequivalent water molecules contained in the Rochelle Salt molecule, one water molecule giving rise to one band, and it is shown that the so-called short hydrogen band does not exist in Rochelle Salt.