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1.
用INDO法对C28X4(X=H,Cl)和CX4(X=H,Cl)进行几何构型优化,得到Td对称性的构型C28X4有4种键、4种不等同原子,基态为稳定的闭壳层分子,以此构型为基础计算了上述分子的电子光谱,并预测C28X4的电子光谱。  相似文献   

2.
The structural, electronic, energy, and vibrational characteristics of the Al13X? and Al13X 2 ? clusters, with an aluminum-centered (Alc) icosahedral cage Al13 and with one or two outer-sphere ligands X=H, F, Cl, Br, OH, NH2, CH3, C6H5, have been calculated within the B3LYP approximation of the density functional theory using the 6-31G* and 6-311+G* basis sets. In all Al13X? radicals, the unpaired electron is localized at the cage atom Al* located opposite the Al-X bond. This Al* atom is the most favorable site for attaching the second X ligand of any nature (trans-addition rule). According to the previously suggested molecular model of the valence state of the [Al 13 ? ] “superatom,” the calculated energies D 1(Al 13 ? -X) of addition of the first ligand to the Al 13 ? anion are about 1 eV lower than the corresponding energies of addition of the second ligand D 2(XAl 13 ? -X). The structure of the Al13 cage depends on the nature of the nature of the substituent X and can radically change in going from anions to their neutral congeners. In the lowest-lying Al13X isomer with electronegative substituents X (Hal, OH, NH2, CH3, etc.), the aluminum cage has a marquee structure (1, symmetry C s) with a hexagonal base and a pentagonal “roof.” For Al13X analogues with electropositive ligands X (Al, Li, Na), a tridentate isomer (T, C 3v ) with the X substituent coordinated to a face of the Al13 icosahedron is preferable. In the case of moderately electronegative X ligands (of the H type), the marquee (1) and icosahedral (T) isomers are close in energy. The stretching vibration frequencies of isomers 1 and T differ significantly in magnitude and intensity so that vibrational spectroscopy methods can be especially applicable to their experimental identification.  相似文献   

3.
C70X2(X=H,F, Cl)的稳定性和电子光谱   总被引:1,自引:0,他引:1  
滕启文  吴师  郝策  赵学庄  唐敖庆  封继康 《化学学报》1997,55(11):1072-1076
用INDO方法研究C70H2四种异构体的稳定性, 表明其最稳定异构体为1, 9-C70H2和7, 8-C70H2, 两者能量差为16.3KJ.mol^-^1, 与实验值及ab initio计算值接近; 光谱计算表明, 其特征吸收峰与实验值一致。在此基础上预测C70F2和C70Cl2的稳定性和电子光谱, 表明C70F2四种异构体的稳定性顺序与C70H2一致, 而C70Cl2则以21, 42-异构体最为稳定。二者的电子光谱与C70H2极其相似只是在500nm以上有细微差别。  相似文献   

4.
Regioselectivity for the 5,8,15,18-substituted isomer over the 5,8,14,17-isomer was observed in a series of mercaptan–bromide coupling reactions leading to the formation of 2,11-dithia[3.3]paracyclophanes. Their molecular assembly was established by X-ray crystallographic studies. In the crystal packing of these paracyclophanes, several types of non-covalent interactions including halogen–halogen interaction, halogen-bonding interaction, weak hydrogen-bonding interaction, etc. are observed in crystals 3a, 3b and 3c. There is evidence to indicate that weak non-covalent Br…Br, Br…S, Br…N, C–H…S, S…S and C–H…N interactions play an important role in governing their molecular assembly assumed in the solid state. The attractive interactions of Br…Br, Br…S and Br…N are also rationalised and supported in terms of the density functional theory calculations.

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5.
用量子化学UMP2方法,在6-311++G**基组水平上研究了CH2X(X=H,F,Cl)与臭氧反应机理,全参数优化了反应过程中反应物、中间体、过渡态和产物的几何构型,在UQCISD(T)/6-311++G**水平上计算了它们的能量,并对它们进行了振动分析,以确定中间体和过渡态的真实性.从CH2X(X=H,F,Cl)与O3的反应机理的研究结果看,它们与O3反应的活性都比较强,相对而言,活性大小顺序为CH2F>CH3>CH2Cl,也就是说,CH2F自由基与臭氧间的反应活性最强,对大气臭氧的损耗将是最大的.同时研究还发现CH2X(X=H,F,Cl)系列自由基与O3的反应都是强放热反应.  相似文献   

6.
The electronic and molecular structures of mono- and dihalocarbene anions constructed by model CX1X2?? (X1, X2 = H, F, Cl, Br, I), as well as the corresponding carbenes CX1X2 and analogous silicon-anions SiX1X2??, have been studied in detail using the B3LYP, MP2, and QCISD(T) levels of theory. Our calculated findings suggest that stabilization of the compounds is associated with the size of the halogen substituent X, which is further confirmed by ionization energies, the spin density (S d), and the second-order perturbative energies (E(2)). Besides, we have also explored the source of the anions’ proton affinity difference.  相似文献   

7.
Quantum chemical calculations using DFT (BP86) and ab initio methods (MP2, MP4 and CCSD(T)) have been carried out for the title compounds. The nature of the Pb?CPb interactions has been investigated with an energy decomposition analysis. The energy minimum structures of the halogen substituted Pb2X2 molecules possess a doubly bridged butterfly geometry A like the parent system Pb2H2. The unusual geometry can be explained with the interactions between PbX fragments in the X 2?? ground state which leads to one Pb?CPb electron-sharing ?? bond and two donor?Cacceptor bonds between the Pb?CX bonds as donor and vacant p(??) AOs of Pb. The energy difference between the equilibrium form A and the linear structure XPb??PbX (E) which is a second-order saddle point is much higher when X is a halogen atom than for X?=?H. This is because the a 4???????X 2?? excitation energies of PbX (X?=?F?CI) are higher than for PbH. The structural isomers B, D1, D2, E, F1, F2 and G of Pb2X2 are no minima on the potential energy surface.  相似文献   

8.
The molecular orbitals for B4H4, B4F4, B4Cl4, B4Br4 and B4I4 have been calculated by using all-electron or effective core potential ab initio method at the self-consistent field level using basis sets with diffuse and polarization functions. The boron-boron and boron-halide (-hydrogen) distances of these cage compounds are optimized with three kinds of basis sets constrained to a tetrahedral symmetry. According to the localization scheme of Boys, four three-centered two-electron (3c2e) B-B-B bonds localized on each of the faces of the B4 tetrahedron are derived for B4X4 clusters. The HOMO-LUMO energy gaps, atomization energies and Mulliken overlap populations of these compounds indicate that the stabilities of the clusters decrease in the sequence of B4F4 > B4Cl4, B4H4 > B4Br4 > B4I4.  相似文献   

9.
用密度泛函B3LYP方法对PuX+(X=H,O,N,C)分子离子体系进行了理论研究.结果表明,这些分子离子的基态电子状态分别是X 7Σ-(PuH+)、X 6Σ-(PuO+)、X 5Σ+(PuN+)和X 8Σ-(PuC+);势能函数为Murrell-Sorbie势函数.并得到了相应的几何性质、力学性质和光谱数据.  相似文献   

10.
Vibrational spectra of the salts M2B12X12 where X = H, D, Cl, Br, I; M = K, Cs are obtained in solid state and in aqueous solution. The vibrational assignment for the undistorted icosahedral anion B12X2−12 in the series X = H, D, Cl, Br, I is discussed. The spectral pattern observed is consistent with the selection rules for the Ih point symmetry group. The changes in the spectra of the solid salts due to the crystal field are revealed.  相似文献   

11.
PuX+(X=H,O,N,C)的结构与势能函数   总被引:8,自引:0,他引:8  
用密度泛函B3LYP方法对PuX+(X=H,O,N,C)分子离子体系进行了理论研究.结果表 明,这些分子离子的基态电子状态分别是X 7Σ-(PuH+)、X 6Σ-(PuO+)、X 5Σ+(P uN+)和X 8Σ-(PuC+);势能函数为Murrell-Sorbie势函数.并得到了相应的几何性质、 力学性质和光谱数据.  相似文献   

12.
《Chemical physics letters》1987,137(2):175-179
A method for constructing empirical potential surfaces is proposed which is based on the BSBL (bond-strength-bond-length) treatment originally developed to predict kinetic parameters for atom transfer reactions. Quasiclassical trajectory results for X + H2 → HX + H (X = F, Cl, Br, I) and the reverse reactions were used to demonstrate the utility of the new PES for the study of the dynamics and kinetics of metathesis reactions.  相似文献   

13.
14.
The electronic spectroscopy of H2X (X=O, Te, Po) was investigated by means of spinorbit configuration interaction (EPCISO) and restricted active space state interaction (SORASSI). The transition energies to the low-lying singlet and triplet states of H2O, in which the SO interaction is zero, compare rather well with the experimental data as well as to other theoretical values. The theoretical electronic absorption spectrum is characterized by three allowed transitions A^1B1 (2px(O)→σ^*g/3s(O)), B^1A1(σg→σ^*g/3s(O)) and A^1S2(σg→σ^*u) calculated at 7.68, 9.94, and 11.72 eV, respectively. The theoretical absorption spectra of H2X (X=Te, Po) are shifted to the red with the A^1B1 (npx(X)→σ^*g) states calculated at 5.06 eV (H2Te) and 4.40 eV (H2Po) and the A^1B2 (σg→σ^*u) states calculated at 7.89 eV (H2Te) and 7.77 eV (H2Po). The largest SO splitting amounts to 0.34 eV and is found for the lowest a^3A1 of H2Po. In H2Te the SO effects are still negligible with a maximum splitting of 0.04 eV for the lowest a^3B2. The two methods lead to comparable results but the EPCISO approach depends strongly on the reference wavefunction.  相似文献   

15.
用量化学UMP2方法,在6-311++G**基组水平上研究了CH_2X(X=H,FCI)与臭氧反 应机理,全参数优化了反应过程中反应物、中间体、过渡态和产物的内何构型,在 UQCISD(T)/6-311++G**水平上计算了它们的能量,并对它们进行了振动分析,以 确定中间体和过渡态的直实性。从CH_2X(X=H,FCI)与O_3的反应机理的研究结果看 ,它们与O_3反应的活性都比较强,相对而言,活性大小顺序为CH_2F>CH_3> CH_2CI,也就是说,CH_2F自由基与臭氧间的反应活性最强,对大气臭氧的损耗将 是最大的。同时研究还发现CH_2X(X=H,FCI)系列自由基与O_3的反应都是强放热反 应。  相似文献   

16.
李来才  邹勤  田安民 《化学学报》2003,61(10):1524-1527
用量化学UMP2方法,在6-311++G**基组水平上研究了CH_2X(X=H,FCI)与臭氧反 应机理,全参数优化了反应过程中反应物、中间体、过渡态和产物的内何构型,在 UQCISD(T)/6-311++G**水平上计算了它们的能量,并对它们进行了振动分析,以 确定中间体和过渡态的直实性。从CH_2X(X=H,FCI)与O_3的反应机理的研究结果看 ,它们与O_3反应的活性都比较强,相对而言,活性大小顺序为CH_2F>CH_3> CH_2CI,也就是说,CH_2F自由基与臭氧间的反应活性最强,对大气臭氧的损耗将 是最大的。同时研究还发现CH_2X(X=H,FCI)系列自由基与O_3的反应都是强放热反 应。  相似文献   

17.
Ab initio MP2/aug’-cc-pVTZ calculations have been carried out to investigate H2CO : PXH2 pnicogen-bonded complexes and HCO2H : PXH2 complexes that are stabilized by pnicogen bonds and hydrogen bonds, with X=NC, F, Cl, CN, OH, CCH, CH3, and H. The binding energies of these complexes exhibit a second-order dependence on the O−P distance. DFT-SAPT binding energies correlate linearly with MP2 binding energies. The HCO2H : PXH2 complexes are stabilized by both a pnicogen bond and a hydrogen bond, resulting in greater binding energies for the HCO2H : PXH2 complexes compared to H2CO : PXH2. Neither the O−P distance across the pnicogen bond nor the O−P distance across the hydrogen bond correlates with the binding energies of these complexes. The nonlinearity of the hydrogen bonds suggests that they are relatively weak bonds, except for complexes in which the substituent X is either CH3 or H. The pnicogen bond is the more important stabilizing interaction in the HCO2H : PXH2 complexes except when the substituent X is a more electropositive group. EOM-CCSD spin-spin coupling constants 1pJ(O−P) across pnicogen bonds in H2CO:PXH2 and HCO2H : PXH2 complexes increase as the O−P distance decreases, and exhibit a second order dependence on that distance. There is no correlation between 2hJ(O−P) and the O−P distance across the hydrogen bond in the HCO2H : PXH2 complexes. 2hJ(O−P) coupling constants for complexes with X=CH3 and H have much greater absolute values than anticipated from their O−P distances.  相似文献   

18.
用密度泛函B3LYP方法对PuX2+(X=O,H,N,C)分子离子进行了理论研究,结果表明:PuO2+,PuH2+,PuN2+和PuC2+分子离子能稳定存在,基态电子状态是X5∑-(PuO2+),X8∑-(PuH2+),X4∑+(PuN2+)和X9∑-(PuC2+),势能函数为Murrell-Sorbie势函数,并导出了相应的几何性质,力学性质和光谱数据.  相似文献   

19.
Ab initio calculations have been carried out in a systematic investigation of P···N pnicogen complexes H(2)XP:NXH(2) for X ═ H, CH(3), NH(2), OH, F, and Cl, as well as selected complexes with different substituents X bonded to P and N. Binding energies for complexes H(2)XP:NXH(2) range from 8 to 27 kJ mol(-1) and increase to 39 kJ mol(-1) for H(2)FP:N(CH(3))H(2). Equilibrium structures have a nearly linear A-P-N arrangement, with A being the atom directly bonded to P. Binding energies correlate with intermolecular N-P distances as well as with bonding parameters obtained from AIM and SAPT analyses. Complexation increases (31)P chemical shieldings in complexes with binding energies greater than 19 kJ mol(-1). One-bond spin-spin coupling constants (1p)J(N-P) across the pnicogen interaction exhibit a quadratic dependence on the N-P distance for complexes H(2)XP:NXH(2), similar to the dependence of (2h)J(X-Y) on the X-Y distance for complexes with X-H···Y hydrogen bonds. However, when the mixed complexes H(2)XP:NX'H(2) are included, the curvature of the trendline changes and the good correlation between (1p)J(N-P) and the N-P distance is lost.  相似文献   

20.
A short review of the works where theoretical models for describing kinetics of catalytic X–H bonds breaking reactions (X = C, O, and H) over metal surfaces were developed on the basis of concepts of the Dogonadze–Kuznetsov–Levich quantum mechanical theory of chemical processes. Numerical values of the rate constants of these reactions over (111) surfaces of nickel, platinum and rhodium, which are considered as steps of a complex catalytic process of methane steam reforming (MSR) are calculated and compared with experimental data. These rate constants are used for simulations of microkinetic models of the MSR reactions on the catalysts. Effects of external parameters on the MSR rates and on isotope effects are described.  相似文献   

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