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1.
Spontaneous Raman spectra in the BaWO4 were measured in the temperature range from 4 K to 280 K, and the temperature dependence of the linewidth of the Ag (191 cm−1) Raman mode was analyzed using the lattice dynamical perturbative approach and one-phonon density of states (PDOS). The linewidth slope for the 191 cm−1 peak for an external mode is 7.2 times larger than that for the 926 cm−1 peak for a breathing mode. The different behaviors of these two modes in the case of temperature broadening could be attributed to the large energy band gap in the one-phonon density of states (PDOS) resulting in different anharmonic interactions. The origin may be that the ratio of up-conversion TDOS to down-conversion TDOS for Eg mode (191 cm−1) is more than that for Ag (926 cm−1). The peak of the Eg mode (191 cm−1) is attributed to the coupling mode both a rotation of the Barium and an out-of-phase rotation of the oxygen in xy plane as a librational mode.  相似文献   

2.
The phosphate mineral series eosphorite–childrenite–(Mn,Fe)Al(PO4)(OH)2·(H2O) has been studied using a combination of electron probe analysis and vibrational spectroscopy. Eosphorite is the manganese rich mineral with lower iron content in comparison with the childrenite which has higher iron and lower manganese content. The determined formulae of the two studied minerals are: (Mn0.72,Fe0.13,Ca0.01)(Al)1.04(PO4, OHPO3)1.07(OH1.89,F0.02)·0.94(H2O) for SAA-090 and (Fe0.49,Mn0.35,Mg0.06,Ca0.04)(Al)1.03(PO4, OHPO3)1.05(OH)1.90·0.95(H2O) for SAA-072. Raman spectroscopy enabled the observation of bands at 970 cm−1 and 1011 cm−1 assigned to monohydrogen phosphate, phosphate and dihydrogen phosphate units. Differences are observed in the area of the peaks between the two eosphorite minerals. Raman bands at 562 cm−1, 595 cm−1, and 608 cm−1 are assigned to the ν4 bending modes of the PO4, HPO4 and H2PO4 units; Raman bands at 405 cm−1, 427 cm−1 and 466 cm−1 are attributed to the ν2 modes of these units. Raman bands of the hydroxyl and water stretching modes are observed. Vibrational spectroscopy enabled details of the molecular structure of the eosphorite mineral series to be determined.  相似文献   

3.
《Vibrational Spectroscopy》2002,28(2):209-221
Syngenite (K2Ca(SO4)2·H2O), formed during treatment of manure with sulphuric acid, was studied by infrared, near-infrared (NIR) and Raman spectroscopy. Cs site symmetry was determined for the two sulphate groups in syngenite (P21/m), so all bands are both infrared and Raman active. The split ν1 (two Raman+two infrared bands) was observed at 981 and 1000 cm−1. The split ν2 (four Raman+four infrared bands) was observed in the Raman spectrum at 424, 441, 471 and 491 cm−1. In the infrared spectrum, only one band was observed at 439 cm−1. From the split ν3 (six Raman+six infrared) bands three 298 K Raman bands were observed at 1117, 1138 and 1166 cm−1. Cooling to 77 K resulted in four bands at 1119, 1136, 1144 and 1167 cm−1. In the infrared spectrum, five bands were observed at 1110, 1125, 1136, 1148 and 1193 cm−1. From the split ν4 (six infrared+six Raman bands) four bands were observed in the infrared spectrum at 604, 617, 644 and 657 cm−1. The 298 K Raman spectrum showed one band at 641 cm−1, while at 77 K four bands were observed at 607, 621, 634 and 643 cm−1. Crystal water is observed in the infrared spectrum by the OH-liberation mode at 754 cm−1, OH-bending mode at 1631 cm−1, OH-stretching modes at 3248 (symmetric) and 3377 cm−1 (antisymmetric) and a combination band at 3510 cm−1 of the H-bonded OH-mode plus the OH-stretching mode. The near-infrared spectrum gave information about the crystal water resulting in overtone and combination bands of OH-liberation, OH-bending and OH-stretching modes.  相似文献   

4.
Raman spectra of coquandite Sb6O8(SO4)·(H2O) were studied, and related to the structure of the mineral. Raman bands observed at 970, 990 and 1007 cm?1 and a series of overlapping bands are observed at 1072, 1100, 1151 and 1217 cm?1 are assigned to the SO42? ν1 symmetric and ν3 antisymmetric stretching modes respectively. Raman bands at 629, 638, 690, 751 and 787 cm?1 are attributed to the SbO stretching vibrations. Raman bands at 600 and 610 cm?1 and at 429 and 459 cm?1 are assigned to the SO42? ν4 and ν2 bending modes. Raman bands at 359 and 375 cm?1 are assigned to O–Sb–O bending modes. Multiple Raman bands for both SO42? and SbO stretching vibrations support the concept of the non-equivalence of these units in the coquandite structure.  相似文献   

5.
The samples of dibarium magnesium orthoborate Ba2Mg(BO3)2 were synthesized by solid-state reaction. The X-ray diffraction (XRD) patterns and Raman spectra of the samples were collected. Electronic structure and vibrational spectroscopy of Ba2Mg(BO3)2 were systematically investigated by first principle calculation. A direct band gap of 4.4 eV was obtained from the calculated electronic structure results. The top valence band is constructed from O 2p states and the low conduction band mainly consists of Ba 5d states. Raman spectra for Ba2Mg(BO3)2 polycrystalline were obtained at ambient temperature. The factor group analysis results show the total lattice modes are 5Eu + 4A2u + 5Eg + 4A1g + 1A2g + 1A1u, of which 5Eg + 4A1g are Raman-active. Furthermore, we obtained the Raman active vibrational modes as well as their eigenfrequencies using first-principle calculation. With the assistance of the first-principle calculation and factor group analysis results, Raman bands of Ba2Mg(BO3)2 were assigned as Eg (42 cm−1), A1g (85 cm−1), Eg (156 cm−1), Eg (237 cm−1), A1g (286 cm−1), Eg (564 cm−1), A1g (761 cm−1), A1g (909 cm−1), Eg (1165 cm−1). The strongest band at 928 cm−1 in the experimental spectrum is assigned to totally symmetric stretching mode of the BO3 units.  相似文献   

6.
《Polyhedron》2005,24(3):451-461
Reaction of 2,9-dioxo-1,4,7,10-tetraazabicyclo[1.10.1]hexadeca-1(11),13,15-triene-4,7-diacetic acid (H2L1) with CuCl2 · 2H2O in ethanol at pH 6 led to the monomeric benzodioxochlorocomplex [Cu(L1)Cl] (1) (HL1 = monoethylesther of H2L1). X-ray structural analysis has shown that in complex 1 the Cu is five-coordinated by two nitrogen and two oxygen atoms of the macrocycle and by a chloride, displaying a square pyramidal coordination geometry. One of the acetate arms does not coordinate to the Cu and has suffered an in situ ethanolic esterification reaction. The protonation constants of H2L1 and the stability constants of its complexes with Cu2+, Ni2+, Zn2+, Cd2+ and Pb2+ were determined by potentiometric methods and in some cases by 1H NMR spectroscopy. The stability constants of the complexes follow the trend [Ni(H1L1)] > [Cu(H1L1)]  [Pb(H1L1)] > [Zn(H1L1)] > [Cd(H1L1)], probably due to steric requirements. Spectroscopic measurements (absorption and EPR) at different pH values have shown the effect of the pH on the coordination sphere of the Cu complexes.  相似文献   

7.
We investigate the nature of bonding and charge states in (U1−yCey)O2 (y = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) by Raman spectroscopy. Raman spectrum of UO2 exhibits two prominent bands below 1000 cm−1, a F2g mode at 446 cm−1 and a F1u LO mode at 578 cm−1. As y is increased from 0 to 0.6, the F1u exhibits a large blue shift of 90 cm−1, and from y = 0.6 to 1.0, a red shift of 54 cm−1. We show that our results can be interpreted as arising from anisotropic compression/relaxation of the lattice under Ce substitution and this can give an indication of its charge states. Alternate interpretations have been given in the literature on the effect of substituents and dopants to the Raman spectra of UO2 and CeO2. The present interpretation of chemical stress effects can be taken as another plausible explanation.  相似文献   

8.
Choline dihydrogen phosphate ([N1.1.1.2OH]DHP) and 1-butyl-3-methylimidazolium dihydrogen phosphate ([C4mim]DHP) were synthesized as a new class of proton-conducting ionic plastic crystals. Both [N1.1.1.2OH]DHP and [C4mim]DHP showed solid–solid phase transition(s) and showed a final entropy of fusion lower than 20 J K−1 mol−1 which is consistent with Timmerman’s criterion for molecular plastic crystals. The ionic conductivity of [N1.1.1.2OH]DHP was in the range of 10−6 S cm−1–10−3 S cm−1 in the plastic crystalline phase. On the other hand, the ionic conductivity of [C4mim]DHP showed about 10−5 S cm−1 in the plastic crystalline phase. [N1.1.1.2OH]DHP showed one order of magnitude higher ionic conductivity than [C4mim]DHP in the temperature range where the plastic phase is stable.  相似文献   

9.
《Polyhedron》2005,24(16-17):2102-2107
Four complexes of M(NO3)2(4NOPy-OMe)2, (4NOPy-OMe = 4-(N-tert-butyloxylamino)-2-(methoxymethylenyl)pyridine, and M = MnII, 1; CoII, 2; NiII, 3; CuII, 4), were prepared and fully characterized. X-ray single crystal analysis reveals that four complexes are isostructural. The molecular structures are distorted octahedral in which the methoxy oxygen atoms coordinate to the metal ion by trans-configuration while the pyridyl nitrogen atoms and the nitrate oxygen atoms coordinate by cis-configuration. The magnetic properties of all complexes were investigated by SQUID magneto/susceptometry. Temperature dependence of the molar magnetic susceptibilities in the temperature range of 2–300 K indicated that the magnetic coupling between aminoxyl radicals and metal ion was antiferromagnetic in the complex 1 and were ferromagnetic in the complexes 24. The quantitative analysis based on the spin Hamiltonian, H = −2J(S1SM + SMS2) yielded the best fit as J/kB = −13.4 ± 0.1 K, g = 1.94 ± 0.002, and θ = −0.78 ± 0.02 K for the complex 1, J/kB = 48.7 ± 2.1 K, g = 2.07 ± 0.02, and θ = −2.83 ± 0.41 K for the complex 3 (the data in the temperature range 300–50 K were used), and J/kB = 57.0 ± 1.2 K, g = 2.002 ± 0.004, and θ = −9.8 ± 0.1 K for the complex 4.  相似文献   

10.
《Vibrational Spectroscopy》2007,43(1):254-259
The low-frequency region of the infrared and Raman spectra of nitric acid hydrates is analyzed. Theoretical calculations of the vibrational normal modes of the crystals of nitric acid monohydrate and the β-phases of the dihydrate and trihydrate are carried out, focusing the results in the regions below 175 cm−1 and near the symmetric stretch of the nitrate ion NO3, around 1000–1100 cm−1. A prediction of the corresponding infrared spectra is presented. A joint study is performed of the calculated normal modes, the predicted IR spectra, and the recently published Raman spectra of these compounds, based on symmetry considerations and using the atomic displacements associated to each normal mode as a further source of information. Although most of the modes present a strong mixture of atomic motions, assignments can be proposed for some of the vibrations.  相似文献   

11.
We present the Raman spectra of l-methionine (C5H11NO2S) monocrystals obtained in the spectral region ranging from 3200 to 50 cm−1 at temperatures from 20 to 375 K. We investigated the dynamics of the different functional groups in l-methionine and related their behaviour to the structural transition previously reported at about 307 K. Additionally, on cooling, changes in the intensities of some Raman bands were associated with conformational changes of at least one of the two l-methionine conformers in the monoclinic unit cell in the interval 160–140 K. Thermal analysis and DFT calculations provide further support to the interpretation of the Raman results.  相似文献   

12.
We calculated IR, nonresonance Raman spectra and vertical electronic transitions of the zigzag single-walled and double-walled boron nitride nanotubes ((0,n)-SWBNNTs and (0,n)@(0,2n)-DWBNNTs). In the low frequency range below 600 cm−1, the calculated Raman spectra of the nanotubes showed that RBMs (radial breathing modes) are strongly diameter-dependent, and in addition the RBMs of the DWBNNTs are blue-shifted reference to their corresponding one in the Raman spectra of the isolated (0,n)-SWBNNTs. In the high frequency range above ∼1200 cm−1, two proximate Raman features with symmetries of the A1g (∼1355 ± 10 cm−1) and E2g (∼1330 ± 25 cm−1) first increase in frequency then approach a constant value of ∼1365 and ∼1356 cm−1, respectively, with increasing tubes’ diameter, which is in excellent agreement with experimental observations. The calculated IR spectra exhibited IR features in the range of 1200–1550 cm−1 and in mid-frequency region are consistent with experiments. The calculated dipole allowed singlet–singlet and triplet–triplet electronic transitions suggesting a charge transfer process between the outer- and inner-shells of the DWBNNTs as well as, upon irradiation, the possibility of a system that can undergo internal conversion (IC) and intersystem crossing (ISC) processes, besides the photochemical and other photophysical processes.  相似文献   

13.
The mineral ettringite has been studied using a number of techniques, including XRD, SEM with EDX, thermogravimetry and vibrational spectroscopy. The mineral proved to be composed of 53% of ettringite and 47% of thaumasite in a solid solution. Thermogravimetry shows a mass loss of 46.2% up to 1000 °C. Raman spectroscopy identifies multiple sulphate symmetric stretching modes in line with the three sulphate crystallographically different sites. Raman spectroscopy also identifies a band at 1072 cm−1 attributed to a carbonate symmetric stretching mode, confirming the presence of thaumasite. The observation of multiple bands in the ν4 spectral region between 700 and 550 cm−1 offers evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 3629 cm−1 is assigned to the OH unit stretching vibration and the broad feature at around 3487 cm−1 to water stretching bands. Vibrational spectroscopy enables an assessment of the molecular structure of natural ettringite to be made.  相似文献   

14.
Raman spectroscopy has been sued to study the antimony containing mineral roméite Ca2Sb2O6(OH,F,O) from three different origins. Roméite is a calcium antimonate mineral of the pyrochlore group. An intense Raman band at ~518 cm?1 for roméite is assigned to the SbO ν1 symmetric stretching mode and the band at 466 cm?1 to the SbO ν3 antisymmetric stretching mode. The Raman band at 303 cm?1 is attributed to the OSbO bending mode. Some variation in band positions is observed and is attributed to the variation in composition between the three mineral samples.  相似文献   

15.
The reaction of [Cp1IrCl2]2 (Cp* = η5  C5Me5) with the tridentate 3-thiapentane-1,5-dithiolate ligand, S(CH2CH2S)2 (tpdt), led to the formation of [Cp1Ir(η3  tpdt)] (1) in 81% isolated yield. Subsequent reactions of 1 with [Cp1IrCl2]2 in 2:1 and 1:1 molar equiv ratios resulted in the formation of [Cp1Ir(μ  η2:η3  tpdt)Cp1IrCl][PF6] (2) and [Cp1Irμ  η2:η3  tpdt)Cp1IrCl][Cp1IrCl3] (3) in 86 and 79% yields, respectively, based on 1, whereas the reactions of 1 with [(COD)IrCl]2 (COD = 1,5-cyclooctadiene) in 2:1 and 1:1 molar equiv ratios resulted in the formation of the homo-bimetallic derivatives Cp1Ir(μ  η1:η3  tpdt)(COD)IrCl (4) (92% yield) and [Cp1Ir(μ  η2:η3  tpdt)(COD)Ir] [(COD)IrCl2] (5) (82% yield). Reactions between 1 and [(COD)RhCl]2, yielded the hetero-bimetallic derivatives Cp1Ir(μ  η1:η3  tpdt)(COD)RhCl (6) and [Cp1Ir(μ  η2:η3  tpdt)(COD)Rh][(COD)RhCl2] (7), in 92 and 93% yields, respectively. The reaction of 1 with methyl iodide gave mono-methylated derivative [Cp1Ir(η3-C4H8S3Me)]I (8) (93% yield). All these compounds have been comprehensively characterized.  相似文献   

16.
《Polyhedron》2005,24(16-17):2242-2249
Two heterobimetallic coordination polymers, [Cu(2,4-pydc)2Mn(H2O)4]x (1) and [Cu(2,5-pydc)2Mn(H2O)2]x · 4xH2O (2), have been synthesized and structurally characterized by single crystal X-ray diffraction. Both compounds have extended 2-D sheet structures. In 1 the copper centers are linked in chains by double ligand bridges and these chains are cross-linked through the manganese coordination spheres and O–C–O bridges to form polymeric sheets. In 2 separate O–C–O bridged Cu and Mn chains are connected in an alternating array by additional ligand bridging to generate the overall 2-D structure. Analysis of magnetic data of 1 reveals that ferromagnetic exchange between the O–C–O bridged copper and manganese centers dominates the magnetic properties of this system. The magnetic data for 2 fit well to a model incorporating antiferromagnetic exchange in independent S = 1/2 and S = 5/2 linear chains with J(Cu) = −0.073 cm−1 and J(Mn) = −0.32 cm−1. Unlike the situation in 1, there is no evidence for heterometallic exchange. In both 1 and 2 the significant exchange occurs via O–C–O bridges. To study the effect of thermal dehydration on the magnetic properties of these systems, the compounds Cu(2,4-pydc)2Mn · H2O (1d) and Cu(2,5-pydc)2Mn · H2O (2d) were synthesized and studied.  相似文献   

17.
《Comptes Rendus Chimie》2014,17(5):490-495
A new complex of [Ni3(dcp)2(H2O)10] (1) (H3dcp = 3,5-pyrazoledicarboxylic acid) has been synthesized from H3dcp and Ni(NO3)2·6H2O by hydrothermal reaction. Complex 1 has the discrete trinuclear structure. Three Ni(II) ions are bridged by two dcp3− ligands, with 10 coordinated water molecules as terminal ligands. The molecules of [Ni3(dcp)2(H2O)10] extend into three-dimensional supramolecular architectures by intermolecular O–H···O hydrogen bonds as well as π-π stacking interactions. Magnetic susceptibility measurement shows that a weak antiferromagnetic interaction is operative between nickel(II) ions and an excellent simulation of the experimental data gives D = 5.27 cm−1, J = −2.19 cm−1 and g = 2.05.  相似文献   

18.
The complexes of [Ln(2,3,4-tmoba)3phen]2 (Ln = Dy (1), Eu (2), Tb (3); 2,3,4-tmoba = 2,3,4-trimethoxybenzoate; phen = 1,10-phenanthroline) were synthesized and characterized by a series of techniques including the elemental analysis, IR and fluorescent spectra and TG/DSC-FTIR technology. The crystal structures were determined by X-ray crystallography. Each complex include two Ln3+ ions, six 2,3,4-tmoBA and two phen molecules forming a binuclear structure, giving the coordination number of nine. The three-dimensional IR accumulation spectra of gaseous products for the complexes 1 to 3 are analyzed and the thermal decomposition processes are further authenticated. Through means of differential scanning calorimeter (DSC), two solid-solid phase transition endothermic peaks were found in the complex 2, which was different from the complexes 1 and 3. The heat capacities of these complexes were measured and fitted to a polynomial equation with the least squares method for each complex on the basis of the reduce temperature x (x = [T  (Tmax + Tmin)/2]/[(Tmax  Tmin)/2]) over the range from (256.15 to 476.15) K. Subsequently, the smoothed molar heat capacities and thermodynamic functions (HTH298.15 K), (STS298.15 K), and (GTG298.15 K) of the complexes 1 to 3 were calculated based on the fitted polynomial of the heat capacities. The fluorescent intensity of the complexes 2 and 3 are markedly improved as well.  相似文献   

19.
《Polyhedron》2005,24(16-17):2269-2273
Two ion-pair compounds, consisting of 1-(4′-R-benzyl)pyridinium ([RBzPy]+, R = NO2 (1) and Br (2)) and [Ni(dmit)2] (dmit2− = 2-thioxo-1,3-dithion-4,5-dithiolato), have been synthesized and structurally characterized. The anions of [Ni(dmit)2] stack into dimers, which further construct into two-leg ladder through terminal S⋯S interactions in 1, lateral S⋯S interactions in 2. The weak H-bonding interactions of C–H⋯S were observed in 2, while only weak van de Waals interactions between anion and cations in 1. The magnetic susceptibilities measured in 2–300 K indicate AFM exchange interaction domination both two compounds. A peculiar magnetic transition at ∼100 K was observed in 1. An AFM ordering below ∼11 K was found in 2, and the best fit to magnetic susceptibility above 45 K in this compound, using a dimer model with s = 1/2, give rise to Δ/kB = 36.1 K, zJ = −0.91 K, C = 3.2 × 10−3 emu K mol−1 and χ0 = −4.0 × 10−6 emu mol−1 with g of 2.0 fixed.  相似文献   

20.
《Tetrahedron: Asymmetry》2005,16(9):1595-1602
The spontaneous resolution reaction of racemic trans-2,3-dihydro-2,3-dipyridyl-benzo[e]indole 1 with Cd(ClO4)2·6H2O in the presence of 2-butanol under solvothermal reaction conditions favors the formation of crystal 2 [P-Cd(R,R,-1)2(ClO4)2], while a similar reaction in the presence of ethanol only favors the formation of crystal 3 [M-Cd(S,S,-1)2(ClO4)2]. The crystal structural determination shows that both 2 and 3 crystallize in chiral enantiomorphous space groups (P6122 and P6522) and their structures are 1D infinite chain, and are just enantiomorphous pairs most like. The spontaneous resolution process displays estimated ee values of ca. +0.6 for 2-butanol and ca. −0.4 for ethanol. Enantiomerically pure (S,S)-trans-2,3-dihydro-2,3-dipyridyl-benzo[e]indole (S,S,-1) can be obtained through the decomposition of mechanically separated 3. Additionally (S,S,-1) also crystallizes in a chiral space group (P21). The CD (circular dichroism) spectra of both 2 and 3 in the solid state are also approximately enantiomorphous pairs. However, their fluorescent spectra in the solid state display a moderate difference in maximum emission peaks (Δλ = 19 nm). Crystal data for 2: C44H34Cl2N6O8Cd, M = 958.07, hexagonal, P6122, a = 10.5488(5), c = 68.256(4) Å, α = γ = 90°, β = 120°, V = 6577.8(6) Å3, Z = 6, Dc = 1.451 mg m−3, R1 = 0.0498, wR2 = 0.1124, μ = 0.679 mm−1, S = 0.623, Flack χ = −0.02(6). For space group P6522, R1 = 0.0670, wR2 = 0.1602, S = 0.725 with a Flack value of 1.03(7); Crystal data for 3, C44H34Cl2N6O8Cd, M = 958.07, hexagonal, P6522, a = 10.5446(3), c = 68.265(3) Å, V = 6573.3(4) Å3, Z = 6, Dc = 1.452 mg m−3, R1 = 0.0444,wR2 = 0.1002, μ = 0.679 mm−1, S = 0.558, Flack χ = 0.01(5). For space group P6122, R1 = 0.0501, wR2 = 0.1178, S = 0.599 with a Flack value of 1.00(5). The low Flack parameter indicates that the absolute configurations of 2 and 3 are stated; Crystal data for (S,S)-1, C22H17N2, M = 323.39, orthorhombic, P212121, a = 9.2598(7), b = 9.4617(8), c = 19.1452(16) Å, V = 1677.4(2) Å3, Z = 4, Dc = 1.281 mg m−3, R1 = 0.0417, wR2 = 0.1191, T = 293 K, μ = 0.077 mm−1, S = 0.862.  相似文献   

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