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1.
The results of theoretical studies on structures and energetics are presented for proton-bound complexes N 2H +–XH, N 2H +–X 2, and N 2H +–XY(YX) (X=Y=F, Cl, and Br). In all the monocations complexes, the halogen atom shares a proton with N 2. The calculated energetic results show that the stability decreases when descending in the corresponding periodic table column. The possible proton transfer dissociation processes of N 2H ++XH, N 2H ++X 2, and N 2H ++XY systems into XH 2+, X 2H +, XYH +, and YXH + and molecular N 2 are calculated to be endothermic for share of the processes. The NBO results show that the largest intermolecular charge transfer is found in the Br bonded complexes. 相似文献
2.
Estertn compounds, (MeO 2CCH 2CH 2) 2SnX 2 [X 2 = I 2 (2); X 2 = Br 2 (9); X 2 = Cl, Br (4)) or X 2 = (NCS) 2 (3)] have been obtained by halide exchange reactions of (MeO 2CCH 2CH 2) 2SnCl 2. Crystal structure determinations of 2–4 revealed chelating MeO 2CCH 2CH 2 units with distorted octahedral geometries at tin. The Sn---O bond lengths in the isothiocyanato complex, 3, are shorter [2.390(11) to 2.498(12), mean 2.439 Å], with the chelate bite angles, C---Sn---O, larger [74.3(7) to 78.2(6), mean 76.0°] than those in the halide analogues 2 and 4 [Sn---O = 2.519(2) to 2.541(8), mean 2.530 Å; C---Sn---O 72.8(3) to 73.9(4), mean 73.3°]. 1H, 13C and 119Sn NMR and IR spectra of 2–4 and 9 were determined in CDCl 3 solution: the NMR spectra of (MeO 2CCH 2CH 2) 2SnX 2 show the following trends: (i) both δ 1H and δ 13C , increase and (ii) both 2J (Sn---H) and 1J( Sn--- C) decrease in the sequence X 2 = (NCS) 2, Cl 2, ClBr, Br 2 and I 2. The MeO 2CCH 2CH 2 and dmio groups (dmio = 1,3-dithiole-2-one-4,5-dithiolato) are all chelating groups in (MeO 2CCH 2CH 2) 2Sn(dmio) (5). As shown by X-ray crystallography, the tin atom in the anion of solid [Q][MeO 2CCH 2CH 2Sn(dmio) 2] 6 (Q = NEt 4) forms 5 strong bonds [to C and the 4 thiolato S atoms, Sn---S 2.459(2) to 2.559(2) Å], arranged in a near trigonal bipyramidal array. There is an additional Intramolecular but weaker, interaction with the carbonyl oxygen atom [Sn---O = 3.111(5) Å]; v(C=O) = 1714 cm −1 in solid 6 (Q = NEt 4). NMR spectra of 5 and 6 are also reported. 相似文献
3.
Calculations on linear and bent structures of N 3 and P 3 show that these species are quite different. N 3 is linear, P 3 is bent almost to a D 3h geometry. The symmetry of P 3 in D 3h is 2E″ but the Jahn-Teller distortion is very small, ≈4°. The many-body expansion of the energy of P n clusters appears to be only slowly convergent. 相似文献
4.
The aim of this work was to study the microwave-assisted pyrolysis of CH 4 over an activated carbon, which acted as both microwave receptor and catalyst, and the influence of using different CH 4/N 2 ratios on the conversion of CH 4 to H 2. In order to compare the results obtained in the microwave oven, the pyrolysis was also carried out under conventional heating (electric furnace, EF). The effects of N 2, which enhanced significantly CH 4 conversion, differed depending on the heating device used. Under EF heating, N 2 seemed to have an effect similar to distribute the CH 4 molecules within the activated carbon bed. Under microwave heating (MW), the N 2, as well as distributing the CH 4 molecules, favoured the generation of energetic microplasmas, leading to higher conversions. The prevalence of one role over the other depended on the CH 4/N 2 ratio, the appearance of energetic microplasmas being favoured with high percentages of N 2. Consequently, CH 4 conversion was higher at low CH 4/N 2 ratios. Additionally, the formation of carbon nanofibres in experiments where a combination of N 2 and MW heating was used is also reported. 相似文献
5.
将沸石咪唑酯骨架结构材料应用于抽放煤层甲烷的浓缩净化研究。以三乙胺(TEA)为导向剂,ZnSO 4为金属离子源,水为溶剂,采用水热合成法进行了ZIF-8吸附剂的制备。采用XRD、物理吸附、动态吸附分离和反相气相色谱(IGC)等方法对ZIF-8的物理结构、化学稳定性、吸附分离性能和热力学性质进行了研究。结果表明,ZIF-8具有良好的化学稳定性,能够在强酸、强碱和强极性的溶剂中保持结构的稳定性;在298 K时,ZIF-8对CH 4/N 2的分离因子达到3.4,与活性炭相当,但CH 4、N 2在ZIF-8上的吸附热比在活性炭上低20%左右。 相似文献
6.
Silane undergoes thermal decomposition on the surface of “phosphorus pentoxide” ( P 4O 10) into its elements around 200–400°C. The hydrogen formed partially reduces the P 4O 10 forming lower oxides of phosphorus and water. Elemental silicon is precipitated as reddish-brown solid, which is separated by dissolving out the phosphorus oxides. Silica and disiloxane are not formed in the reaction. 相似文献
7.
LnCl 3 (Ln=Nd, Gd) reacts with C 5H 9C 5H 4Na (or K 2C 8H 8) in THF (C 5H 9C 5H 4 = cyclopentylcyclopentadienyl) in the ratio of 1 : to give (C 5H 9C 5H 4)LnCl 2(THF) n (orC 8H 8)LnCl 2(THF) n], which further reacts with K 2C 8H 8 (or C 5H 9C 5H 4Na) in THF to form the litle complexes. If Ln=Nd the complex (C 8H 8)Nd(C 5H 9C 5H 4)(THF) 2 (a) was obtained: when Ln=Gd the 1 : 1 complex [(C 8H 8)Gd(C %H 9)(THF)][(C 8H 8)Gd(C 5H 9H 4)(THF) 2] (b) was obtained in crystalline form. The crystal structure analysis shows that in (C8H8)Ln(C5H9C5H4)(THF)2 (Ln=Nd or Gd), the Cyclopentylcyclopentadieny (η5), cyclooctatetraenyl (η8) and two oxygen atoms from THF are coordinated to Nd3+ (or Gd3+) with coordination number 10. The centroid of the cyclopentadienyl ring (Cp′) in C5H9C5H4 group, cyclooctatetraenyl centroid (COTL) and two oxygens (THF) form a twisted tetrahedron around Nd3+ (or Gd3+). In (C8H8)Gd(C5H9C5H4)(THF), the cyclopentyl-cyclopentadienyl (η5), cyclooctatetraenyl (η8) and one oxygen atom are coordinated to Gd3+ with the coordination number of 9 and Cp′, COT and oxygen atom form a triangular plane around Gd3+, which is almost in the plane (dev. -0.0144 Å). 相似文献
8.
A novel N6 macrocyclic ligand, L 1 (2,8,14,20-tetramethyl-3,7,15,19,25,26-hexaaza-tricyclo[19.3.1.1 9,13]hexacosa-1(24),9,11,13(26),21(25),22-hexaene), was obtained by reduction of the 2 + 2 condensation product of 2,6-diacetylpyridine and propane-1,3-diamine. Zinc(II) complexes of L 1, of a related N8 macrocycle, L 3 (3,6,9,17,20,23,29,30-octaaza-tricyclo[23.3.1.1[11,15]]triaconta-1(28),1,13,15(30),25(29),26-hexaene), similarly prepared by 2 + 2 condensation of 2,6-diformylpyridine and diethylenetriamine and of a tetra N-2-cyanoethyl derivative of a homologue of L 1 prepared from diformyl pyridine and ethane-1,2-diamine, L 2 (3-[6,14,17-tris-(2-cyano-ethyl)-3,6,14,17,23,24-hexaaza-tricyclo[17.3.1.1 8,12] tetracosa-1(23),8(24),9,11,19,21-hexaen-3-yl]-propionitrile), were prepared. Structures were determined for [ZnL 1](ClO 4) 2 · H 2O, [ZnL 2](NO 3) 2 and [Zn 2L 3(NO 3) 2](NO 3) 2 · H 2O. The [ZnL 1](ClO 4) 2 · H 2O and [ZnL 2](NO 3) 2 complexes present a mononuclear endomacrocyclic structure with the metal in an octahedral distorted environment coordinated by the six donor nitrogen atoms from the macrocyclic backbone while the complex [Zn 2L 3(NO 3) 2](NO 3) 2 · H 2O is dinuclear with both metal atoms into the macrocyclic cavity coordinated by four donor nitrogen atoms from the macrocyclic framework and one oxygen atom from one monodentate nitrate anion, in a distorted square pyramidal arrangement. 相似文献
9.
Using pseudopotentials and double zeta basis sets with s, p diffuse functions and two sets of d functions, MRD-CI calculations were performed on As 2(±), As 4(+), GaAs −, GaAs 2(±) and Ga 2As 2(±). This study complements previous theoretical investigations on Ga (±) to Ga 4(±) and GaAs (+). For As 4 tetrahedral symmetry was assumed, and Re of X 1A 1 determined as 4.73 a0. Vertical ionization potentials to several states of As 4+ were calculated. For GaAs 2, GaAs 2+ and GaAs 2−, ground and one low-lying state were geometry-optimized, both in C 2v (Ga-As-As), and linear symmetry (GaAsAs, C ∞h and AsGaAs, D ∞h). The lowest state of GaAs 2 is 2B 2 in C 2v. For Ga 2As 2, the lowest state and low-lying excited states were optimized in various geometries. The most stable state has rhombic structure ( 1A g in D 2h), but T-form and other forms (C 2v, C ∞v, D ∞h) are only 1–2 eV less stable. In D 2h symmetry, several low-lying excited states of Ga 2As 2 were studied. The ground states of Ga 2As 2+ and Ga 2As 2− were found to be 2B 2u, and 2B 2g, respectively. Trends in ionization potentials (IP), electron affinities (EA), atomization energies and fragmentation energies for the molecules Ga xAs y and the pure compounds Ga n and As n up to 4 atoms, were studied. Ga xAs y clusters, with x + y even, have higher IP's than odd-numbered clusters. An experimentally observed alternation of EA, whereby an odd number of atoms have higher EA than their even neighbors, is confirmed. The mixed compounds Ga xAs y have atomization energies between those of Ga n and As n ( x + y = n), usually closer to those of Ga n. Fragmentation of Ga xAs y occurs such that As----As bonds are retained, and if possible, also Ga----As bonds, since the dissociation energy of As 2 is higher than that of GaAs, which in turn is higher than that of Ga 2. Calculated fragmentation energies agree qualitatively with experimental observations about the composition of 3-atomic and 4-atomic clusters Ga xAs y. 相似文献
10.
The addition of Cl, NH 3, CO, C 6H 6 to Ti 8C 12 has been investigated by means of ab initio RHF and DFT calculations. The metallocarbohedrene (met-car) molecule has been modelled as a structure of a tetracapped tetrahedron with T d symmetry and two distinct metal sites, found to be most stable from previous theoretical investigations. The addition of four molecules to the atoms of the external tetrahedron of metal atoms has been found to be exothermic for all ligands considered. The addition of four extra ligands leading to T 8C 12(L) 8 appears easy for L = Cl, and also for L = NH 3. It appears that π-bonding molecules, either non-polar like benzene or weakly polar like CO, have much less affinity for the inner tetrahedron of metal atoms, which makes adducts with eight ligands difficult or impossible to obtain in that case. Those results agree with the recently observed reactivity of met-cars. 相似文献
11.
以TEAOH和TMAOH为有机模板剂,酸处理的UZM-9分子筛为晶种,采用水热法在48 h内合成出分子筛UZM-9,并对其CO 2/CH 4/N 2的吸附分离性能进行了研究。采用XRD、ICP、TG、SEM与气体吸附等手段对晶种法合成的UZM-9分子筛结构、耐水稳定性与吸附性能进行了研究。结果表明,晶种法可以在2 d内合成出硅铝原子比在3以上、收率达到65%的UZM-9分子筛;所得分子筛的CO 2吸附容量可以达到5 mmol/g以上,吸附热为34 kJ/mol,CO 2/CH 4、CO 2/N 2与CH 4/N 2的平均分离因子分别为100、240与2.4,CO 2分离性能优良且具有一定耐水性能。 相似文献
12.
The molecular structure of TeCl 2Br 2 in the vapour phase is reconsidered in the light of the recently published X-ray crystal structure for TeCl 4. Normal coordinate calculations are performed on molecular TeCl 2Br 2 in its three possible symmetries using force fields derived from the parent molecules TeCl 4 and TeBr 4. The calculations indicate that the data for molecular TeCl 2Br 2 can best be interpreted as arising from a mixture of at least the two high symmetry conformers rather than just the low symmetry C1 molecule as previously reported. 相似文献
13.
The geometric structure of c-C 4F 8SF 4 has been determined by gas-phase electron diffraction. The five-membered ring has the twist form ( C2 symmetry) with a puckering amplitude q = 0.42 (2) Å. The following principle geometric parameters ( ra values) with estimated uncertainties have been derived: (C---C) av = 1.541(10), S---C = 1.896(7), S---F e = 1.558(6), S---F a = 1.594(6) Å, CSC = 90.0(9)°, SCC = 109.1(8)°, CCC = 106.5(12)°, F aSF e = 90.5(15)° and F eSF e = 87.7(29)°. Vibrational amplitudes for long non-bonded CF and FF distances indicate a high barrier to pseudorotation of the ring. 相似文献
14.
Ab initio molecular orbital calculations of nuclear spin-spin coupling constants in PH −2, PH 3, PH +4 and P 2H 4 have been carried out employing SCF perturbation theory. Basis set dependence of all the four contributing terms has been studied in order to find the criterion for the selection of basis sets to be employed for computing this property. The dependence of the coupling constants of PH −2 on its geometry has also been found. This study also discusses the requirement for satisfactory computation of couplings in cases where none of the coupling nuclei is a proton. It is found that bond-centred functions along with at least double zeta basis sets reproduce coupling constants quite satisfactorily. In all the cases studied, uncontracted core basis functions yield couplings which are in better agreement with experimental couplings than those obtained with contracted core functions. 相似文献
15.
We present a detailed investigation of the quantum efficiency of the 1S 0 and 3P 0,1 levels in Pr 3+ doped YF 3 under VUV excitation. The quantum efficiency of the 3P 0,1 level was determined by the measurement and comparison of the photon fluxes of the 1S 0 → 1I 6 transition around 400 nm with the visible emissions occurring from the 3P 0,1 levels. It was found that already at concentrations as low as 0.01% the 3P 0,1 emission quantum efficiency is only about 61%. The quenching process is most probable caused by an energy transfer cross relaxation process involving the 3P 0,1 levels and the 3H 4 ground state. For concentrations of 0.1%, 0.5%, 1% and 10%, the quantum efficiency was determined to be about 42%, 29%, 17%, and 0.4%, respectively. The total quantum efficiency of the visible emission (380–750 nm) under excitation at 190 nm, determined by measurements of the total photon flux, has a maximum for a Pr 3+ concentration of 1%. At this value, the absorption efficiency of the 4f5d absorption bands is very high and the 3P 0,1 quenching is only moderate. 相似文献
16.
The vanadium(V) peroxo phosphato complex K 7[V 4O 4(O 2) 8(PO 4)]·9H 2O has been obtained from the KVO 3---KH 2PO 4---KOH---H 2O 2---H 2O---C 2H 5OH system. The X-ray structural analysis revealed a tetranuclear anionic structure in which two dinuclear [V 2O 2(O) 2) 2(μ-η 1 : η 2-O 2) 2] units are connected by the μ 4-PO 4 group. 相似文献
17.
[Re 2(Ala) 4(H 2O) 8](ClO 4) 6 (Re=Eu, Er; Ala=alanine) were synthesized, and the low-temperature heat capacities of the two complexes were measured with a high-precision adiabatic calorimeter over the temperature range from 80 to 370 K. For [Eu 2(Ala) 4(H 2O) 8](ClO 4) 6, two solid–solid phase transitions were found, one in the temperature range from 234.403 to 249.960 K, with peak temperature 243.050 K, the other in the range from 249.960 to 278.881 K, with peak temperature 270.155 K. For [Er 2(Ala) 4(H 2O) 8](ClO 4) 6, one solid–solid phase transition was observed in the range from 270.696 to 282.156 K, with peak temperature 278.970 K. The molar enthalpy increments, Δ Hm, and entropy increments,Δ Sm, of these phase transitions, were determined to be 455.6 J mol −1, 1.87 J K −1 mol −1 at 243.050 K; 2277 J mol −1, 8.43 J K −1 mol −1 at 270.155 K for [Eu 2(Ala) 4(H 2O) 8](ClO 4) 6; and 4442 J mol −1, 15.92 J K −1 mol −1 at 278.970 K for [Er 2(Ala) 4(H 2O) 8](ClO 4) 6. Thermal decompositions of the two complexes were investigated by use of the thermogravimetric (TG) analysis. A possible mechanism for the thermal decomposition is suggested. 相似文献
18.
The reaction between Ru 2Cl(μ-O 2CCH 3) 4 and molten p-tert-butylbenzamide led to the formation of Ru 2Cl(μ-HNOCC 6H 4- p-CMe 3) 4. The polymeric structure of this insoluble compound was broken with AgBF 4, in anhydrous thf, giving [Ru 2(μ-HNOCC 6 H 4- p-CMe 3) 4(thf) 2]BF 4. The reaction of this cationic complex with OPPh 3 gave [Ru 2(μ-HNOCC 6H 4- p-CMe 3) 4(OPPh 3) 2]BF 4. The compounds have been characterized by elemental analysis, spectroscopic data and magnetic measurements and the crystal structure of [Ru 2(μ-HNOCC 6H 4- p-CMe 3) 4(OPPh 3) 2]BF 4 was determined by X-ray crystallography. The asymmetric unit is composed of halves of two different crystallographically independent centrosymmetric cations. Each ruthenium(II,III) dimer is bonded to four bridging p-tert-butylbenzamidate ligands and to two axial triphenylphosphine oxide molecules. The Ru---Ru distances in the two dimeric cations of the unit cell are 2.281(2) and 2.280(2) Å. The compound has a non-polar 2 : 2 arrangement of the tert-butylbenzamidate ligands. 相似文献
19.
The arsenic oxide pressure of As 2O 5 has been studied using mass spectrometry and a transportation method. Mass spectrometry revealed the presence of the species As 4O +6, As 4O +7, and As 4O +8 in the vapour. The existence of volatile species up to As 4O 10(g) as a result of the reaction As 4O 10(g) As 4O (10−y) (g) +1/2 yO 2(g) has been assumed. The oxygen pressure of this equilibrium builds up very slowly. The equilibrium pressure can be expressed by log(pO2/atm) (880−952 K) = −(13940±930)/T + (14.53 ± 1.01) A stationary arsenic oxide pressure has been measured using the transportation method. Since the oxygen pressure in the transportation gas did not influence the arsenic oxide pressure, it is assumed that only the As4O10(g) pressure has been measured. The results can be expressed by the linear function log(pAs4O10/atm) (865−1009 K) = −(15741 ± 410)/T + (13.87 ± 0.42). 相似文献
20.
The X-ray structure of [S 4N 3]Cl reveals three independent molecules, which all display π-facial interactions between the Cl − and the pseudo-aromatic [S 4N 3] + rings to produce a structure containing “inverse sandwich” systems. 相似文献
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