共查询到20条相似文献,搜索用时 15 毫秒
1.
E. D. Jemmis K. T. Giju K. Sundararajan K. Sankaran V. Vidya K. S. Viswanathan J. Leszczynski 《Journal of Molecular Structure》1999,510(1-3):59-68
The details of weak C–Hπ interactions that control several inter and intramolecular structures have been studied experimentally and theoretically for the 1:1 C2H2–CHCl3 adduct. The adduct was generated by depositing acetylene and chloroform in an argon matrix and a 1:1 complex of these species was identified using infrared spectroscopy. Formation of the adduct was evidenced by shifts in the vibrational frequencies compared to C2H2 and CHCl3 species. The molecular structure, vibrational frequencies and stabilization energies of the complex were predicted at the MP2/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels. Both the computational and experimental data indicate that the C2H2–CHCl3 complex has a weak hydrogen bond involving a C–Hπ interaction, where the C2H2 acts as a proton acceptor and the CHCl3 as the proton donor. In addition, there also appears to be a secondary interaction between one of the chlorine atoms of CHCl3 and a hydrogen in C2H2. The combination of the C–Hπ interaction and the secondary ClH interaction determines the structure and the energetics of the C2H2–CHCl3 complex. In addition to the vibrational assignments for the C2H2–CHCl3 complex we have also observed and assigned features owing to the proton accepting C2H2 submolecule in the acetylene dimer. 相似文献
2.
通过将C_9H_(10)O_2-0.5ZnCl_2双酸型低共熔溶剂固载到Al_2O_3上制备了C_9H_(10)O_2-0.5ZnCl_2/Al_2O_3催化剂。该催化剂采用XRD、FT-IR、SEM、EDS、N_2吸附-脱附技术进行了分析。以C_9H_(10)O_2-0.5ZnCl_2/Al_2O_3为催化剂,过氧化氢为氧化剂研究模拟油中芳香族硫化物的脱除性能。考察反应参数如温度、催化剂加入量、O/S物质的量比、硫化物类型等对催化剂脱硫活性的影响。实验结果表明,在模拟油为5 mL、催化剂量为0.2 g、O/S比为8、反应温度为60℃、反应时间为180 min的条件下,模拟油中二苯并噻吩(DBT)脱硫率为99.2%。此外,在模拟油氧化脱硫中催化剂循环使用六次,其氧化脱硫活性略有降低。研究了C_9H_(10)O_2-0.5ZnCl_2/Al_2O_3催化氧化脱硫的反应机理。 相似文献
3.
The ab initio molecular structures and vibrational frequencies for several transition metal heptoxides X2O7n− (n=0, 2, 4) were calculated using effective core potentials at the HF and DFT (B3LYP) levels. The relative merits of different valence basis set arrangements were tested by comparison with experimental results available, in particular with gas-phase Re2O7 molecular structure and vibrational frequencies. The calculations were then extended to other heptoxides of the VB, VIB and VIIB transition metal groups. The results indicate that a staggered geometry (either D3d or C2) is the energy minimum for most of the heptoxides studied. The only exceptions are Mn2O7, which clearly prefers an eclipsed C2v(syn) configuration, and Tc2O7, for which C2 and C2v(syn) geometries have nearly the same energy.
Particular attention was given to the magnitude of the X–O–X bond angle, as this structural parameter has been a matter of some controversy. The calculated values range from 125° (Mn2O7) to 180° (Group VB heptoxides) and depend on the position of the transition metal in the Periodic Table. A tendency for linearity of the X–O–X moiety on going both downwards the group and backwards the period was observed and discussed. 相似文献
4.
M. Carme Rovira Juan J. Novoa Myung-Hwan Whangbo Jack M. Williams 《Chemical physics》1995,200(3):319-335
On the basis of ab initio MP2/6–31 + + G(2d,2p) calculations, we examined the potential energy surfaces of the water·hydrocarbon complexes H2O·CH4, H2O·C2H2 and H2O·C2H2 to locate all the minimum energy structures and estimate the hydrogen bond energies and vibrational frequencies associated with the C(spn)---H·O and the O---H·C(spn) bonds (n = 1−3). Our calculations show that H2O·C2H2, H2O·C2H4 and H2O·CH4 have two minimum energy structures (i.e., the C---H·O and O---H·C hydrogen bond forms), but H2O·C2H4 has only one when the vibrational motion is taken into account, the O---H·C hydrogen bond form. We have also computed the barrier for the interconversion from one minimum to the other. The fully optimized geometries of H2O·CH4, H2O·C2H4 and H2O·C2H2 as well as the vibrational shifts of the C---H stretching frequencies in their C---H·O hydrogen-bonded forms are in good agreement with the available experimental data. The calculated hydrogen bond energies show that the C(spn---H·O bond strengths decrease in the order C(sp)---H·O>C(sp2)---H·O>C(sp3)---O>C(sp3---H·O, which is also consistent with the available experimental data. 相似文献
5.
Bo-Cheng Wang Likey Chen Kuei-Jen Lee Chang-Yuan Cheng 《Journal of Molecular Structure》1999,469(1-3):127-134
The spectral analysis indicates that all isomers of C60O, C70O and C60O2 have an epoxide-like structure (an oxygen atom bridging across a C–C bond). According to the geometrical structure analysis, there are two isomers of fullerene monoxide C60O (the 5,6 bond and the 6,6 bond), eight isomers of fullerene monoxide C70O and eight isomers of fullerene dioxide C60O2. In order to simulate the real reaction conditions at 300 K, the calculation of the different isomers of C60O, C60O2 and C70O fullerene oxides was carried out using the semiempirical molecular dynamics method with two different approaches: (a) consideration of the geometries and thermodynamic stabilities, and (b) consideration of the ozonolysis mechanism. According to the semiempirical molecular dynamic calculation analysis, the probable product of this ozonolysis reaction is C60O with oxygen bridging over the 6–6 bond (C2v). The most probable product in this reaction contains oxygen bridging across in the upper part of C70 (6–6 bond in C70O-2 or C70O-4) an epoxide-like structure. C60O2-1, C60O2-3 and C60O2-5 are the most probable products for the fullerene dioxides. All of these reaction products are consistent with the experimental results. It is confirmed that the calculation results with the semiempirical molecular dynamics method are close to the experimental work. The semiempirical molecular dynamics method can offer both the reaction temperature effect by molecular dynamics and electronic structure, dipole moment by quantum chemistry calculation. 相似文献
6.
利用凝胶溶胶法和浸渍法制备了Ce-Fe/Al2O3/cordierite催化剂,实验研究了其催化丙烷选择性还原NO的特性。结果表明,当铈的负载量从1%增加至5%时,Ce-Fe/Al2O3/cordierite的C3H8-SCR性能先增强后减弱,3.5Ce-Fe/Al2O3/cordierite具有最佳的脱硝性能,在有氧条件下,600℃时可实现96.5%的脱硝效率。Ce的加入能够提升Fe/Al2O3/cordierite催化剂的抗硫性能。烟气中通入0.02%的SO2后,3.5Ce-Fe/Al2O3/cordierite催化丙烷还原NO的转化率始终维持在93%,而没有经过Ce修饰的Fe/Al2O3/cordierite的NO转化率从88%下降为80%左右。利用XRD、N2吸附-脱附、SEM、H2-TPR、吡啶吸附红外光谱等手段研究了催化剂的物理化学性质。结果表明,加入助剂铈能与Fe形成了固溶体,增加催化剂表面Lewis酸浓度和氧化还原能力,从而提高了催化丙烷还原NO的性能。过多的铈引入会减少Fe2O3结晶体的形成,不利于在C3H8-SCR反应中形成NO2/NO3-物种,从而导致NO还原效率下降。 相似文献
7.
The pure rotational Raman spectra of C214N2 and C215N2 have been recorded photographically using a 3-metre spectrograph with a reciprocal linear dispersion of 1.4 cm−1 mm−1 at 488.0 nm and analysed to give the rotational and centrifugal distortion constants for both species. Corrections were applied to compensate for the effect of molecules in excited vibrational states on the pure rotational spectra. Comparisons are made with previous infrared vibration—rotational studies on these species and with previous Raman studies on C214N2. The following bond lengths were calculated: r0(C---N) = 116 ± 1 pm; r0(C---C) = 138 ± 2 pm. 相似文献
8.
B. L. Khandelwal A. K. Singh N. S. Bhandari 《Journal of organometallic chemistry》1987,320(3):283-288
In the reaction of 3,3-bis(chloromercury)-2,4-pentanedione with TeCl4, Ph2TeCl2, or Ph3TeCl, the replacement of one HgCl group by a tellurium moiety gives Cl3Te(C5H6O2)HgCl·2C4H8O2 (I), Ph2Te(Cl)(C5H6O2)HgCl (II) and Ph3Te(C5H6O2)HgCl (III), respectively. The IR and 1H NMR data indicate that the Te is bonded to the C3 carbon of acetylacetone. In solution the compounds appear to ionize into Cl− and an organometallic cation in which Hg seems to be involved in secondary interaction with the carbonyl groups; far IR and mass spectral data suggest that Hg---O interaction is significant even in solid state. 相似文献
9.
采用溶胶凝胶法和浸渍法制备了负载于蜂窝陶瓷上的Co/Fe/Al2O3/cordierite催化剂,在陶瓷管流动反应器上对其催化C3H6选择性还原NO的性能进行了测试。结果表明,该催化剂表现出最优脱硝性能,在模拟烟气条件下,当反应温度为550 ℃时可实现97%的脱硝效率。Co的引入可显著增强Fe/Al2O3/cordierite催化剂抗SO2和H2O的能力。在模拟烟气中同时引入0.02% SO2和3% H2O后,1.5Co/Fe/Al2O3/cordierite的脱硝性能受影响甚微,当反应温度高于500 ℃时1.5Co/Fe/Al2O3/cordierite催化C3H6还原NO的效率均可达到90%以上;相比之下,未经Co修饰的催化剂Fe/Al2O3/cordierite脱硝性能受到了严重的抑制,在整个反应温度区间(200-700 ℃)内,其催化C3H6还原NO的效率最高不足50%。XRD和SEM表征结果表明,经过适量的Co修饰后的1.5Co/Fe/Al2O3/cordierite表面变得更疏松,且形成了以钴铁和钴铝双金属氧化物为主要成分的球状晶粒。H2-TPR结果表明,相比于Fe/Al2O3/cordierite,1.5Co/Fe/Al2O3/cordierite有更好的低温还原性能。Py-FTIR结果表明,Co的引入可使催化剂表面的Lewis酸明显增加,且生成了Brønsted酸。N2吸附-脱附表征结果表明,Co可增大催化剂的比表面积。 相似文献
10.
Electronic energies, geometries, and harmonic vibration frequencies for the reactants, products, and transition state for the Cl(3P)+C2H6→C2H5+HCl abstraction reaction were evaluated at the HF and MP2 levels using several correlation consistent polarized-valence basis sets. Single-point calculations at PMP2, MP4, QCISD(T), and CCSD(T) levels were also carried out. The values of the forward activation energies obtained at the MP4/cc-pVTZ, QCISD(T)/cc-pVTZ, and CCSD(T)/cc-pVTZ levels using the MP2/cc-pVTZ structures are equal to −0.1, −0.4, and −0.3 kcal/mol, respectively. The experimental value is equal to 0.3±0.2 kcal/mol. We found that the MP2/aug-cc-pVTZ adiabatic vibration energy for the reaction (−2.4 kcal/mol) agrees well with the experimental value −(2.2–2.6) kcal/mol. Rate constants calculated with the zeroth-order interpolated variational transition state (IVTST-0) method are in good agreement with experiment. In general, the theoretical rate constants differ from experiment by, at most, a factor of 2.6. 相似文献
11.
R. P. Shibaeva V. F. Kaminskii E. E. Kostyuchenko E. B. Yagubskii 《Journal of organometallic chemistry》1984,260(3):293-299
The structure of the (C18H8Se3O2)2(C6H5CN) molecular complex isolated from the TSeT + HgI2 reaction in benzonitrile has been determined. The -Se-Se-Se- fragment has been found to have Se---Se bond lengths equal to 2.348(3) and 2.350(4) Å. 相似文献
12.
Yanjuan Qi Yonghui Wang Hongmei Li Minhua Cao Changwen Hu Enbo Wang Ninghai Hu Hengqing Jia 《Journal of Molecular Structure》2003,650(1-3):123-129
The hydrothermal reactions of vanadium oxide starting materials with divalent transition metal cations in the presence of nitrogen donor chelating ligands yield the bimetallic cluster complexes with the formulae [{Cd(phen2)2V4O12]·5H2O (1) and [Ni(phen)3]2[V4O12]·17.5H2O (2). Crystal data: C48H52Cd2N8O22V4 (1), triclinic.
a=10.3366(10), b=11.320(3), c=13.268(3) Å, =103.888(17)°, β=92.256(15)°, γ=107.444(14)°, Z=1; C72H131N12Ni2O29.5V4 (2), triclinic.
a=12.305(3), b=13.172(6), c=15.133(4), =79.05(3)°, β=76.09(2)°, γ=74.66(3)°, Z=1. Data were collected on a Siemens P4 four-circle diffractometer at 293 K in the range 1.59° <θ<26.02° and 2.01°<θ<25.01° using the ω-scan technique, respectively. The structure of 1 consists of a [V4O12]4− cluster covalently attached to two {Cd(phen)2}2+ fragments, in which the [V4O12]4− cluster adopts a chair-like configuration. In the structure of 2, the [V4O12]4− cluster is isolated. And the complex formed a layer structure via hydrogen bonds between the [V4O12]4− unit and crystallization water molecules. 相似文献
13.
《Journal of organometallic chemistry》2002,650(1-2):84-90
Reaction of YbI2 with two equivalents of cyclopentylindenyl lithium (C5H9C9H6Li) affords ytterbium(II) substituted indenyl complex (C5H9C9H6)2Yb(THF)2 (1) which shows high activity to ring-opening polymerization (ROP) of lactones. The reaction between YbI2 and cyclopentylcyclopentadienyl sodium (C5H9C5H4Na) gives complex [(C5H9C5H4)2Yb(THF)]2O2 (2) in the presence of a trace amount of O2, the molecular structure of which comprises two (C5H9C5H4)2Yb(THF) bridged by an asymmetric O2 unit. The O2 unit and ytterbium atoms define a plane that contains a Ci symmetry center. 相似文献
14.
Using geometry optimization and DFT method at the B3LYP/6-31G* level of theory for C30H20, an equilibrium geometry is identified that has the form of polyhedral hydrocarbon with five carbon–carbon single bonds linking a dodecahedrane cage and a pentaprismane cage. Thus, this molecule is a tri-cage molecule with two pentaprismane cages and one dodecahedrane cage. Vibrational frequencies and the infrared spectrum are computed at the same level of theory. The heat of formation for C30H20 has been estimated in this paper. The heat of formation of C30H20 as well as the vibrational analysis indicates that this molecule enjoys sufficient stability to allow for its experimental preparation. 相似文献
15.
Matrix isolation has been combined with infrared spectroscopy to study the reaction chemistry of CrCl2O2 with (CH3)2O and (CH3)2CO. Very similar results were obtained with twin jet and room temperature merged jet deposition, indicating that the initial product forms on the surface of the matrix during deposition, not in the deposition lines prior to matrix condensation. The initial product in both systems was identified as the 1:1 complex between the two reagents, with a structure in which the oxygen atom of the base donates electron density to the Cr center. A number of perturbed vibrational modes of both subunits were observed; for the bases, these modes were vibrations involving the oxygen atom. Hg arc irradiation of the CrCl2O2·O(CH3)2 complex led to growth of a secondary product that is tentatively identified as Cl2CrO(OCH3)2. The CrCl2O2·OC(CH3)2 complex was not photosensitive, and no rearrangements were observed. 相似文献
16.
Sung-Chul Lee Jea-Hun Jang Byung-Yong Lee Jun-Sik Kim Misook Kang Sang-Bong Lee Myung-Jae Choi Suk-Jin Choung 《Journal of molecular catalysis. A, Chemical》2004,210(1-2):131-141
We investigated catalytic behavior of iron in CO2 hydrogenation with and without a ruthenium component. Calcined iron-based catalysts were reduced by H2 and characterized by XRD, BET surface area and CO2, CO and C2H4 temperature-programmed desorption (TPD), and tested for CO2 hydrogenation. When Fe-K/γ-Al2O3 was used as a catalyst, CO2 conversion was 36%, but when Fe-Ru-K/γ-Al2O3 was used, CO2 conversion was 41%. The product selectivities for catalysts with and without the ruthenium component were also compared. Fe-K/γ-Al2O3 exhibited higher methane (16 mol%) and C2–C4 selectivity (39.6 mol%) than Fe-Ru-K/γ-Al2O3. The main products obtained with Fe-Ru-K/γ-Al2O3 were higher hydrocarbons such as C5+ hydrocarbons. For Fe-Ru-K/γ-Al2O3, the product distribution followed the Anderson–Schultz–Flory (ASF) distribution. However, in the case of Fe-Ru-K/γ-Al2O3, the hydrocarbon distribution deviates from the ideal ASF distribution. It is concluded that the readsorption rates of the primary hydrocarbon product increase exponentially with chain length in the ruthenium promoted catalytic system. The behavior of catalysts with and without the ruthenium will be explained by the CO2-, CO- and C2H4– profiles. In this study, it was confirmed that ruthenium component promoted the readsorption ability of -olefin, and then the chain length of hydrocarbon is higher. In addition, the microcrystalline wax produced in CO2 hydrogenation was a high-crystalline and olefin-rich hydrocarbon. 相似文献
17.
The harmonic frequencies and infrared intensities of C9, C11 and C13 have been calculated using SCF and complete active space SCF (CASSCF) methods. The ordering of the harmonic frequencies in C9 is predicted wrongly unless at least the π HOMO and LUMO are included in the active space. Infrared intensities depend crucially on the size of the active space. For linear odd-numbered clusters C13 and larger, the computed SCF spectrum is qualitatively wrong. The recent observation of a band near 1809 cm−1 in the gas phase is explained using our CASSCF results on C13. 相似文献
18.
Michael B. Hursthouse Richard L. Short Brian Piggott Alan Tucker Swee Fatt Wong 《Polyhedron》1986,5(12):2121-2122
Dissolution of Mo2O5((CH3)2NCH2CH2NHCH2CH2S)2 in dimethylformamide results in the formation of a species without coordinated sulphur, as indicated by 95Mo NMR spectroscopy. Subsequent crystallization of this solution yielded the compound Mo4O12(C12H30N4S2)2(C3H7ON)2 which X-ray crystallography shows to consist of a novel Mo4O12 core, containing an eight-membered Mo4O4 ring with the two pairs of diagonal molybdenum atoms linked by disulphido-containing groups. 相似文献
19.
Roland Roesler Warren E. Piers Masood Parvez 《Journal of organometallic chemistry》2003,680(1-2):218-222
The bright red title compound 1 was synthesized from (2-lithiophenyl)diphenylamine and bis(pentafluorophenyl)boron chloride. Its reactions with small acids like H2O and HCl proceeded easily giving zwitterionic compounds. For 1 and its water adduct 2 the crystal structures were determined, the latter featuring an ammonium borate structure containing a short intramolecular hydrogen bond bridge. Treatment of 1 with Jutzi's acid, [H(OEt2)2][B(C6F5)4], did not result in protonation of the nitrogen, but reaction of 1 with LiH in the presence of 12-crown-4, led to the isolation of the aminoborate [1-(Ph2N)-2-{B(H)(C6F5)2}C6H4][Li(12-crown-4)] (3). Borohydride 3 reacted with Jutzi's acid to regenerate 1 and liberate hydrogen. 相似文献
20.
The complexes, M[M(C2O4)3]·xH2 O, where x=4 for M=Cr(III), x=2 for M=Sb(III) and x=9 for M=La(III) have been synthesized and their thermal stability was investigated. The complexes were characterized by elemental analysis, IR and electronic spectral data, conductivity measurement and powder X-ray diffraction (XRD) studies. The chromium(III)tris(oxalato)chromate(III)tetrahydrate (COT), Cr[Cr(C2 O4)3]·4H2O, released water in a stepwise fashion. Removal of the last trace of water was accompanied by a partial decomposition of the oxalate group. Thermal investigation using TG, DTG and DTA techniques in air produced Cr2O3 at 858°C through the intermediate formation of Cr2O3 and CrC2O4 at around 460°C. While DSC study in nitrogen up to 670°C produced a mixture of Cr2O3 and CrC2O4. In antimony(III)tris(oxalato)antimonate(III)dihydrate (AOD), Sb[Sb(C2O4)3]·3H2O the dehydration took place during the decomposition of precursor at 170–290°C and finally at ca. 610°C Sb2 O5 along with trace amounts of Sb2O4 were produced. Trace amount of Sb2O3 and Sb along with Sb2O is proposed as the end product at 670°C of AOD in nitrogen. The oxide La2O3 is formed at 838°C from the study with TG, DTG and DTA in air of lanthanum(III)tris(oxalato)lanthanum(III)nonahydrate (LON), La[La(C2O4)3]·9H2O. Intermediate dioxycarbonate, La2O2CO3 was generated at 526°C prior to its decomposition to lanthanum oxide in air; whereas in N2 the formation of La2(CO3)3 at 651°C was proposed. The thermal parameters have been evaluated for each step of the dehydration and decomposition of COT, AOD and LON using five non-mechanistic equations i.e. Flynn and Wall, Freeman and Carroll, Modified Freeman and Carroll, Coats–Redfern and MacCallum–Tanner equations. Kinetic parameters, such as, E*, ko, ΔH*, ΔS* etc. were also supplemented by DSC studies in nitrogen for all the three complexes. Some of the intermediate species have been identified by analytical and powder XRD studies. Tentative schemes has been proposed for the decomposition of all three compounds in air and nitrogen. 相似文献