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1.
Pure nesquehonite (MgCO3·3H2O)/Mg(HCO3)(OH)·2H2O was synthesised and characterised by a combination of thermo‐Raman spectroscopy and thermogravimetry with evolved gas analysis. Thermo‐Raman spectroscopy shows an intense band at 1098 cm−1, which shifts to 1105 cm−1 at 450 °C, assigned to the ν1CO32− symmetric stretching mode. Two bands at 1419 and 1509 cm−1 assigned to the ν3 antisymmetric stretching mode shift to 1434 and 1504 cm−1 at 175 °C. Two new peaks at 1385 and 1405 cm−1 observed at temperatures higher than 175 °C are assigned to the antisymmetric stretching modes of the (HCO3) units. Throughout all the thermo‐Raman spectra, a band at 3550 cm−1 is attributed to the stretching vibration of OH units. Raman bands at 3124, 3295 and 3423 cm−1 are assigned to water stretching vibrations. The intensity of these bands is lost by 175 °C. The Raman spectra were in harmony with the thermal analysis data. This research has defined the thermal stability of one of the hydrous carbonates, namely nesquehonite. Thermo‐Raman spectroscopy enables the thermal stability of the mineral nesquehonite to be defined, and, further, the changes in the formula of nesquehonite with temperature change can be defined. Indeed, Raman spectroscopy enables the formula of nesquehonite to be better defined as Mg(OH)(HCO3)·2H2O. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

2.
The infrared (IR) spectra of water–ethanol (EtOH) solutions of HCl are measured over a wide range of acid concentration at fixed H2O―EtOH ratios (1 : 1, 1 : 2, and 1 : 40). In these systems, different proton disolvates with (quasi)symmetrical H‐bonds are formed. Their structure and vibrational features are revealed by the density functional theory method coupled with the polarizable continuum model of solvation. In dilute acidic solutions, the Zundel‐type H5O2+ ion is mainly formed. In concentrated HCl solutions, the ions (H2O···H···O(H)Et)+ and (Et(H)O···H···O(H)Et)+ with the quasi‐symmetrical O···H+···O unit having O···O separation <2.45 Å appear. The first ion characterized by the IR‐intensive band around 1800 cm?1 is mainly formed in the 1 : 1 water–ethanol systems. The second ion exists in the 1 : 2 and 1 : 40 water–ethanol systems. Its spectroscopic signatures are the groups of the IR‐intensive bands around 800 and 1050 cm?1. In highly concentrated HCl solutions with the 1 : 40 water–ethanol ratio, a neutral Et(H)O···H+···Cl? complex exists. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

3.
The thermal dehydration of ZnK4(P3O9)2 · 6H2O was studied in the range 25–500°C by thermogravimetric analysis (TGA and DSC) and X‐ray diffraction. We found, based on the TGA and DSC scans, the dehydration of this salt takes place in three stages with a loss of the six water molecules. The infrared and Raman spectra of ZnK4(P3O9)2 · 6H2O have been recorded and interpreted using a factor group analysis. The internal modes are assigned in terms of POP and PO2 structural units using experimental and theoretical IR and Raman frequencies.  相似文献   

4.
Insight into the unique structure of hydrotalcites (HTs) has been obtained using Raman spectroscopy. Gallium‐containing HTs of formula Zn4 Ga2(CO3)(OH)12 · xH2O (2:1 ZnGa‐HT), Zn6 Ga2(CO3)(OH)16 · xH2O (3:1 ZnGa‐HT) and Zn8 Ga2(CO3)(OH)18 · xH2O (4:1 ZnGa‐HT) have been successfully synthesised and characterised by X‐ray diffraction (XRD) and Raman spectroscopy. The d(003) spacing varies from 7.62 Å for the 2:1 ZnGa‐HT to 7.64 Å for the 3:1 ZnGa‐HT. The 4:1 ZnGa‐HT showed a decrease in the d(003) spacing, compared to the 2:1 and 3:1 compounds. Raman spectroscopy complemented with selected infrared data has been used to characterise the synthesised gallium‐containing HTs. Raman bands observed at around 1050, 1060 and 1067 cm−1 are attributed to the symmetric stretching modes of the (CO32−) units. Multiple ν3 (CO32−) antisymmetric stretching modes are found between 1350 and 1520 cm−1, confirming multiple carbonate species in the HT structure. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 710 and 717 cm−1 and assigned to the ν4 (CO32−) modes support the concept of multiple carbonate species in the interlayer. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

5.
Fluoridezirconate crystallohydrates ZnZrF6 · nH2O (n = 6–2) and anhydrous ZnZrF6 are investigated by vibrational spectroscopy and thermography. The influence of the hydrate number on the structure of the cationic and anionic sublattices of the crystallohydrates is studied. The changes in the strength of HOH···F and HOH···O hydrogen bonds of coordinated and outer-sphere water molecules occurring with variations in the hydrate number are determined by changes in the IR spectra. The IR spectra of ZnZrF6 · nH2O (n =6, 4) compounds, which have isolated complex anions [ZrF6]2– in their structure, revealed a band with two peaks in the range of 3470–3430 cm–1, which corresponds to stretching vibrations of coordinated water molecules. The spectra of ZnZrF6 · nH2O (n = 5, 3, 2, 1) crystallohydrates with a polymeric structure show a high-frequency shift of this band, which corresponds to weakening of hydrogen bonds. The vibrations of crystallization water molecules involved in the network of strong O–H···F and O–H···O hydrogen bonds manifest themselves in the spectra of ZnZrF6 · nH2O (n =5, 3) crystallohydrates by broad structureless bands in the region of stretching, bending, and libration vibrations.  相似文献   

6.
《Solid State Ionics》1988,26(2):63-69
Layered phosphonate salts of divalent metal ions (Mg, Ca and Mn) are prepared by combining solutions of soluble metal salts and alkyl- or arylphosphonic acids. In this way the compounds Mg(O3PCnH2n+1)·H2O (n=1−12), Mg(O3PC6H5)·H2O, Mg(HO3PCH(C6H5)2)2·8 H2O, Mn(O3PCH3)·H2O, Mn(O3PC6H5)·H2O, Ca(O3PCnH2n+1)·H2O (n⩽5), Ca(HO3PC6H5)2 and Ca(HO3PCnH2n+1)2 (n⩾6) were prepared. The M(O3PC6H5)·H2O compounds show good thermal stability, losing lattice water at 250–300°C without further decomposition below 550°C. Compounds derived from alkylphosphonic acids decompose at lower temperatures. The Mg(O3PCnH2n+1)·H2O series, Mg(O3PC6H5)·H2O, and Mn(O3PC6H5)·H2O group Pmn21; for the latter compound unit cell dimensions (Å) are a=5.733, b=14.298, c=4.931. The structure consists of roughly coplanar layers of metal atoms coordinated by phenylphosphonate groups above and below. Each metal atom is coordinated by five phosphonate oxygens and one lattice water molecule. Mg(O3PCnH2n+1·H2O adopts a similar structure; infrared spectra indicate all-trans alkyl chains. In Mg(HO3PCH(C6H5)2)2·8 H2O, Mg(H2O)2+6 ions and lattice water lie in hydrogen-bonded sheets; the benzhydryl groups lie above and below and make van-der-Waals contacts between layers.  相似文献   

7.
The Raman spectra of synthetic compounds equivalent to the variscite group: FeAsO4·2H2O AlAsO4·2H2O, GaAsO4·2H2O, and InAsO4·2H2O are reported. In particular, upon comparison of FeAsO4·2H2O to AlAsO4·2H2O, it is observed that the Type II (weak) H‐bond lengths in the latter are slightly longer, which is postulated to affect the stability (As release) in water at pH 5 and 7. Arsenate stretching and bending vibrations were found to be distinct in terms of spectral structure and therefore well suited for fingerprinting. The calculated As O bond strengths from existing crystallographic data showed no significant variations. The strongest ν1 (AsO43−) stretch was used to monitor the As O bonding interactions in the four As O M units, where a shift of 114 cm−1 was observed in the order FeAsO4·2H2O (lowest) < InAsO4·2H2O < GaAsO4·2H2O < AlAsO4·2H2O (highest); this order also followed exactly the measured arsenic release of these phases. This shift in ν1 (AsO43−) position was rationalized to stem from the differences in the electronegativities of the M3+ cations. The trends mentioned above were verified and found to also hold for the isostructural phosphate analogues strengite (FePO4·2H2O) and variscite (AlPO4·2H2O) using published data. Therefore, it is postulated that, as observed with the stability of solution complexes, there may be a correlation between the electronegativity of the M3+ cation in these isostructural phases and their stability (As or P release) in water. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

8.
Raman 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.  相似文献   

9.
Some properties of rare earth orthophosphates have been determined by means of synthesis, X-ray diffraction, infrared absorption spectra, and Raman spectra measurements. The results are: (1) a synthesis of new compounds GdPO4.2H2O weinschenkite type, (2) the salt readily lost its water and changed from the weinschenkite to the xenotime form at about 300°C in air, (3) the change phase in rare earth orthophosphates showed that the weinschenkite phase can give rise to rhabdophane or xenotime phases, and (4) the orthorhombic form DyPO4·1.5H2O is explainable in terms of a mixture of rhabdophane and xenotime-structured material.  相似文献   

10.
Cleavage of disulfide bonds is a common method used in linking peptides to proteins in biochemical reactions. The structures, internal rotor potentials, bond energies, and thermochemical properties (ΔfH°, S°, and Cp(T)) of the S–S bridge molecules CH3SSOH and CH3SS(=O)H and the radicals CH3SS?=O and C?H2SSOH that correspond to H‐atom loss are determined by computational chemistry. Structure and thermochemical parameters (S° and Cp(T)) are determined using density functional Becke, three‐parameter, Lee–Yang–Parr (B3LYP)/6‐31++G (d, p), B3LYP/6‐311++G (3df, 2p). The enthalpies of formation for stable species are calculated using the total energies at B3LYP/6‐31++G (d, p), B3LYP/6‐311++G (3df, 2p), and the higher level composite CBS–QB3 levels with work reactions that are close to isodesmic in most cases. The enthalpies of formation for CH3SSOH, CH3SS(=O)H are ?38.3 and ?16.6 kcal mol?1, respectively, where the difference is in enthalpy RSO–H versus RS(=O)–H bonding. The C–H bond energy of CH3SSOH is 99.2 kcal mol?1, and the O–H bond energy is weaker at 76.9 kcal mol?1. Cleavage of the weak O–H bond in CH3SSOH results in an electron rearrangement upon loss of the CH3SSO–H hydrogen atom; the radical rearranges to form the more stable CH3SS· = O radical structure. Cleavage of the C–H bond in CH3SS(=O)H results in an unstable [CH2SS(=O)H]* intermediate, which decomposes exothermically to lower energy CH2 = S + HSO. The CH3SS(=O)–H bond energy is quite weak at 54.8 kcal mol?1 with the H–C bond estimated at between 91 and 98 kcal mol?1. Disulfide bond energies for CH3S–SOH and CH3S–S(=O)H are low: 67.1 and 39.2 kcal mol?1. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

11.
The frequency and temperature dependence of real and imaginary parts of the dielectric constant (ε′,?ε″), the phase shift (?) and the ac-conductivity (σ) of polycrystalline complexes (β-CD)2·BaI7·11H2O and (β-CD)2·CdI7·15H2O (β-CD?=?β-cyclodextrin) has been investigated over the frequency and temperature ranges 0–100?kHz and 140–420?K in combination with their Raman spectra, DSC traces and XRD patterns. The ε′(T), ε″(T) and ?(T) values at frequency 300?Hz in the range T<330?K show two sigmoids, two bell-shaped curves and two minima respectively revealing the existence of two kinds of water molecule, the tightly bound and the easily movable. Both complexes show the transition of normal hydrogen bonds to flip-flop type at 201?K. In the β-Ba complex most of the eleven water molecules remain tightly bound and only a small number of them are easily movable. On the contrary, in the β-Cd case the tightly bound water molecules are transformed gradually to easily movable. Their DSC traces show endothermic peaks with onset temperatures 118°C, 128°C for β-Ba and 106°C, 123°C, 131°C for β-Cd. The peaks 118°C, 106°C, 123°C are related to the easily movable and the tightly bound water molecules, while the peaks at 128°C, 131°C are caused by the sublimation of iodine. The activation energy of Ba2+ ions is 0.52?eV when all the water molecules exist in the sample and 0.99?eV when the easily movable water molecules have been removed. In the case of β-Cd the corresponding activation energies are 0.57?eV and 0.33?eV. The Raman peaks at 179?cm?1, 170?cm?1 and 165–166?cm?1 are due to the charge transfer interactions in the polyiodide chains.  相似文献   

12.
The dispersion of permittivity and conductivity of crystals containing aqua complexes of different types (γ-HBO2, Ca2B6O11 · H2O, La[B5O8]OH)2 · 1.5H2O, and TRB6O9(OH)3(TR-Tb, Tu)) is studied for the first time. The compounds were synthesized under hydrothermal conditions at T = 270–280°C and P = 70–100 atm. Depending on the contained aqua complex, the compounds display different temperature and frequency behavior of the electric properties. The measurements are carried out in the frequency range from 10?2 to 106 Hz and in the temperature range from ?20 to 140°C.  相似文献   

13.
A theoretical study on the nature of hydrogen bond for formamide and its heavy complexes (CYHNH2···XH; Y?O, S, Se, Te; X?F, HO, NH2) was performed on the basis of density functional theory and the quantum chemistry analysis. Except for the CYHNH2···NH3 complexes, the substitution of O atom at formamide with less electronegative atoms (S, Se, and Te) is found to weaken the hydrogen bond (H‐bond). This substitution results in cyclic structure of hydrated and ammoniated formamide complexes by the formation of bifunctional H‐bonds (Y···H4X; X···H3C). Natural bond orbital analysis indicates that the H‐bond is weakened because of less charge transfer from a lone pair orbital of H‐bond acceptor to antibonding orbital of H‐bond donor. The quantum theory of atoms in molecules analysis reveals that the acyclic structure with single H‐bond stabilizes the complexes more than the cyclic structure formed by bifunctional H‐bonds. Natural energy decomposition analysis (NEDA) and block‐localized wavefunction energy decomposition (BLW‐ED) analyses show that the H‐bond stabilization energies of NEDA and BLW‐ED have good correlation with the dissociation energy of formamide complexes and charge transfer from donor to acceptor atom play an important role in H‐bonding. We have also studied the low‐lying electronic excited states (T1, T2, and S1) for CYHNH2···H2O complexes to explore the nature of H‐bond on the basis of electronegativity and found that NEDA also establishes a good correlation with relative electronic energy (with respect to their ground state) and H‐bond strength at their excited states. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

14.
Insight into the unique structure of layered double hydroxides has been obtained using a combination of X‐ray diffraction and Raman spectroscopy. Indium‐containing hydrotalcites of formula Mg4In2(CO3)(OH)12· 4H2O [2:1 In‐LDH (layered double hydroxides)] through to Mg8In2(CO3)(OH)18· 4H2O (4:1 In‐LDH) with variation in the Mg : In ratio have been successfully synthesized. The d(003) spacing varied from 7.83 Å for the 2:1 LDH to 8.15 Å for the 3:1 indium‐containing layered double hydroxide. Raman spectroscopy complemented with selected infrared data has been used to characterize the synthesized indium‐containing layered double hydroxides of formula Mg6In2(CO3)(OH)16· 4H2O. Raman bands observed at around 1058, 1075 and 1115 cm−1 are attributed to the symmetric stretching modes of the CO32− units. Multiple ν3 CO32− antisymmetric stretching modes are found at around 1348, 1373, 1429 and 1488 cm−1 in the infrared spectra. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 690 and 700 cm−1 assigned to the ν4 CO32− modes support the concept of multiple carbonate species in the interlayer. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

15.
The Raman spectra in FeCl2 · 2H2O (FC2) and the isomorphic compounds FeCl2 · 2D2O (FC2D), MnCl2 · 2H2O (MC2) and CoCl2 · 2H2O (CC2) were observed at 2 K to obtain the frequencies of all 12 optical phonons of even symmetry at the zone center. The lowest of these phonons is known to be coupled resonantly to the magnons below TN. This coupling and other important magnetic properties of the iron salts are determined by the influence of the crystal field. The electronic transitions of the Fe2+-ion in a crystal field are identified after a thorough assignment of the phonon lines in the four isomorphic compounds to symmetry types, using back-scattering and 90°-scattering techniques.  相似文献   

16.
How does the endo C–F bond influence the excess electron binding motif? For lithium‐doped endohedral perfluorofullerenes with endo C–F bonds, under both internal‐push (from exo C–F bonds) and external‐push (from endo C–F bonds) electron effects, the singly occupied molecular orbital electron cloud of the sphere‐like Li···F8@C60F52 (D2) is partially dispersed within the σp–s antibonding orbital of endo C–F bonds and the space between Cδ+–Fendoδ– double electric layers, which makes Li···F8@C60F52 have partial excess electron (electride characteristics) and partial lithium salt characteristics, while in the tube‐like Li···F2@C60F58 (Cs), as the Li is changing from approaching F to keeping away from F and to approaching another one, the singly occupied molecular orbital electron cloud is mainly dispersed from within the p orbital of the short endo C–F bond to within the middle of the two F atoms and again to within the p orbital of the short endo C–F bond, which indicates an evolution from lithium salt characteristic to excess electron characteristic, and again to lithium salt characteristic. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

17.
The relative mobility of nitro and fluoro substituents in 1,3‐dinitro‐ and 1‐fluoro‐3‐nitrobenzenes, 3,5‐dinitro‐ and 3‐fluoro‐5‐nitrobenzotrifluorides under the action of the nucleophiles (2ArYH)·K2CO3 and ArY?K+ in solution and the nucleophiles ArYH·K2CO3 (Y = O, S) under heterogeneous conditions was studied by a competitive method in DMF at 40–140 °C. The unique dependences of ΔΔH on ΔΔS and ΔΔH on ΔΔG were determined for all the substrates and nucleophiles. The dependence of the mechanistic pathway on the nucleophile is discussed. Two results are relevant to the reactions studied: (i) substituent effects in the nucleophiles (2ArYH)·K2CO3 and ArYH·K2CO3 on the activation entropies suggest that the entropy favours the displacement of nitro group; (ii) the negative signs of ΔΔH and ΔΔS for the reactions of the nucleophiles ArY?K+ indicate that the enthalpy determines the displacement of nitro group. It is concluded that the selectivity of the reactions with aryloxide and arylthioxide ions cannot be explained by the hard–soft acid–base principle only. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

18.
Insight into the unique structure of hydrotalcites has been obtained using Raman spectroscopy. Gallium‐containing hydrotalcites of formula Mg4Ga2(CO3)(OH)12· 4H2O (2:1 Ga‐HT) to Mg8Ga2(CO3)(OH)20· 4H2O (4:1 Ga‐HT) have been successfully synthesized and characterized by X‐ray diffraction and Raman spectroscopy. The d(003) spacing varied from 7.83 Å for the 2:1 hydrotalcite to 8.15 Å for the 3:1 gallium‐containing hydrotalcite. Raman spectroscopy complemented with selected infrared data has been used to characterize the synthesized gallium‐containing hydrotalcites of formula Mg6Ga2(CO3)(OH)16· 4H2O. Raman bands observed at around 1046, 1048 and 1058 cm−1 are attributed to the symmetric stretching modes of the CO32− units. Multiple ν3 CO32− antisymmetric stretching modes are found at around 1346, 1378, 1446, 1464 and 1494 cm−1. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 710 and 717 cm−1 assigned to the ν4 (CO32−) modes support the concept of multiple carbonate species in the interlayer. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

19.
Crystalline Li(I), Na(I), K(I), Mg(II), Ca(II), Sr(II), Ba(II) and Cd(II) salts of inosine 5′-monophosphoric acid, H2(IMP), were obtained and characterized by Raman spectroscopy. Splitting of the imidazolic 1480 cm−1 band was observed for the N(7)-bound Ca(IMP)·6H2O, Ba(IMP)·6H2O, Sr(IMP)·6H2O and Cd(IMP)·4H2O compounds. The Li(I), Mg(II), Ca(II) and Cd(II) ions bind directly to the phosphate group, and no direct coordination involving the carbonyl C(6)O group was observed in the compounds reported here. Some Raman spectral features in the 750–700 cm−1 range seem to reflect the nucleoside structure of the inosine moiety  相似文献   

20.
The absorption spectra of CeCl3·7 H2O, LaCl3·7 H2O, CeCl3·7 D2O and LaCl3·7 D2O have been measured at low temperatures in the region of the 4 f→4 f infrared transitions. The energy levels of the Ce3+-ion in these compounds have been derived. The infrared phonon transitions have also been determined from the reflection spectra of these crystals measured in the region between 4000 cm?1 and 50 cm?1. Some of the energy levels of the Ce3+-ions in the deuterated crystals are shifted for about 10 wavenumbers against those in CeCl3·7 H2O. These shifts are probably due to an interaction of the electronic levels with resonant phonon-states in one or the other of the two compounds.  相似文献   

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