^1^7O, ^3^3S NMR化学位移结构效应的分子力学研究

本文通过对环状磷酸酯和环状亚磷酸酯类化合物的分子力学计算,观察到^1^7ONMR化学位移的变化同时受到氧原子局部范德华相互综合利用(E~V~D~W~-~O)和局部偶极相互作用能(E~i~i~p-~O)的影响。此外,在上述两类化合物中,环外氧原子的δ-压缩效应极为明显,这主要是由于该氧原子局部范德华相互作用能起决定作用的缘故。同时,经对二烷基砜类化合物的分子力学计算,首次获得^3^3SNMR化学位移和硫原子局部范德华相互作用能E~V~D~W~-~S之间良好的线性关系。     

次氟酸分子的势能函数及其振动光谱的同位素效应的理…

用三原子振动激发态的变分计算程序（ＴＲＩＡＴＯＭ）精确计算次氟酸分子Ｈ＾１６ＯＦ的振动激发态的能级以及次氯酸分子中的Ｈ和Ｏ分别被Ｄ和＾１８Ｏ取代后Ｈ＾１８ＯＦ，Ｄ＾１６Ｏｆ和Ｄ＾１８ＯＦ的同位素效应，理论计算值与已有的实验结果吻合较好，预测了一些尚水观测到的谱线频率及同位素效应，并确立了一个同位素位移的加和规则。     

有机硒化合物的^7^7Se NMR研究

本文测定了一系列二茂铁有机硒衍生物及几种烷基硒醚、芳基硒醚化合物的^7^7Se NMR谱。确定了这些化合物的^7^7Se NMR化学位移值。着重讨论了影响^7^7Se化学位移的因素。与硒直接相连取代基的链长、支链化程度以及吸电子能力的改变对^7^7Se NMR化学位移有着不同程度的影响。除此之外, 溶剂效应对二茂铁有机硒类化合物的^7^7Se NMR化学位移也有一定程度的影响。     

次氟酸分子的势能函数及其振动光谱的同位素效应的理论研究

用三原子振动激发态的变分计算程序(TRIATOM)精确计算次氟酸分子H¹⁶OF的振动激发态的能级以及次氯酸分子中的H和O分别被D和¹⁸O取代后的H¹⁸OF,D¹⁶)OF和D¹⁸OF的同位素效应,理论计算值与已有的实验结果吻合较好。预测了一些尚未观测到的谱线频率及同位素效应,并确立了一个同位素位移的加和规则。     

LaOX-Pr^3^+(X=Cl, Br)体系的荧光特性及其配位场理论解析

LaOX-Pr^3^+(X=Cl,Br)体系在室温和液氮温度下均只观察到^3P~0能级的发射,其原因在于Pr^3^+离子的4f5d激发态具有较高能量(>37kK),且^3P~2,^3P~1向^3P~0存在有效的电子驰豫;本文基于DSCPCF配位场模型的计算结果,对该体系的发射光谱和激发光谱进行了理论归属,实测峰位与计算值较好吻合。     

(CX~3)~2CO,CF~3COX和CXCl~3(X=H或D)对CH(A,B)自由基的猝灭

本文报道室温下用266nm激光光解-荧光猝灭方法测定CH_3COCH_3,CD_3COCD_3,CF_3CO_2H,CF_3CO_2D,CHCl_3和CDCl_3分子猝灭电子激发态CH(A,B)自由基的速率常数,考察了含不同同位素原子的猝灭剂分子对CH(A,B)猝灭的同位素效应.实验发现,含D的分子比相应含H的分子对CH(A,B)的猝灭具有更大的速率常数.     

固体化合物YbCl~2和AYbI~3(A=Cs,Rb, K)中^1^7^1Yb NMR谱 及核磁屏蔽性质

首次在室温下测定了^1^7^1Yb在YbCl~2中的化学位移、化学位移各向异性、自旋-晶格弛豫时间、自旋-晶格弛豫时间的各向异性,计算出自旋-自旋弛豫时间。根据TMS(^1H)的绝对屏蔽常数,计算了^1^7^1Yb在YbCl~2和在AYbI~3(A=K,Rb,Cs)中的平均绝对屏蔽常数(σ~i~s~o),逆磁绝对屏蔽常数(σ~i~s~o^d)和顺磁绝对屏蔽常数(-σ~i~s~o^p),并且对^1^7^1Yb的各项屏蔽常数与结构之间的关系进行了讨论。     

α-和β-K6H[GeW9V3O40].xH2O的合成及其^5^1V和^1^8^3W核磁共振研究

本文报道了α-和β-K6H[GeW9V3O40].xH2O的合成及其^5^1V和^1^8^3W NMR研究。^5^1V NMR谱只有一个单峰, ^1^8^3W NMR谱中有两个峰, 相对强度为2:1, 其^2J~w~-~o~-~-~w偶合常数分别为19.35和16.73Hz, 表明其阴离子分别为A型α-和β-Keggin结构, 即三个VO6八面体是角顶共用。     

天然丰度氘核磁共振测定一级和二级动力学氘同位素效应（Ⅲ）——对Grignard

本文报道了用天然丰度^2HNMR测定一级动力学氘同位素效应的方法。这种方法与现有方法不同，它要求在反应时授氢反应物大大过量于受氢底物，在计算时要考虑由^2HNMR测定的反应物和产物的特定部位同位素比率（D／H）i或化合物的平均同位素比率（D／H）。我们用这种方法研究了一些Grignard试剂水解的同位素效应。     

(CX~3)~2CO,CF~3COX和CXCl~3(X=H或D)对CH(A,B)自由基的猝灭

本文报道室温下用266nm激光光解-荧光猝灭方法测定CH~3COCH~3,CD~3COCD~3,CF~3CO~2H,CF~3CO~2D,CHCl~3和CDCl~3分子猝灭电子激发态CH(A,B) 自由基的速率常数,考察了含不同同位素原子的猝灭剂分子对CH(A,B)猝灭的同位素效应. 实验发现,含D的分子比相应含H的分子对CH(A,B)的猝灭具有更大的速率常数     

Unimolecular rate constants for HX or DX elimination (X = F, Cl) from chemically activated CF3CH2CH2Cl, C2H5CH2Cl, and C2D5CH2Cl: threshold energies for HF and HCl elimination

Vibrationally activated CF(3)CH(2)CH(2)Cl molecules were prepared with 94 kcal mol(-1) of vibrational energy by the combination of CF(3)CH(2) and CH(2)Cl radicals and with 101 kcal mol(-1) of energy by the combination of CF(3) and CH(2)CH(2)Cl radicals at room temperature. The unimolecular rate constants for elimination of HCl from CF(3)CH(2)CH(2)Cl were 1.2 x 10(7) and 0.24 x 10(7) s(-1) with 101 and 94 kcal mol(-1), respectively. The product branching ratio, k(HCl)/k(HF), was 80 +/- 25. Activated CH(3)CH(2)CH(2)Cl and CD(3)CD(2)CH(2)Cl molecules with 90 kcal mol(-1) of energy were prepared by recombination of C(2)H(5) (or C(2)D(5)) radicals with CH(2)Cl radicals. The unimolecular rate constant for HCl elimination was 8.7 x 10(7) s(-1), and the kinetic isotope effect was 4.0. Unified transition-state models obtained from density-functional theory calculations, with treatment of torsions as hindered internal rotors for the molecules and the transition states, were employed in the calculation of the RRKM rate constants for CF(3)CH(2)CH(2)Cl and CH(3)CH(2)CH(2)Cl. Fitting the calculated rate constants from RRKM theory to the experimental values provided threshold energies, E(0), of 58 and 71 kcal mol(-1) for the elimination of HCl or HF, respectively, from CF(3)CH(2)CH(2)Cl and 54 kcal mol(-1) for HCl elimination from CH(3)CH(2)CH(2)Cl. Using the hindered-rotor model, threshold energies for HF elimination also were reassigned from previously published chemical activation data for CF(3)CH(2)CH(3,) CF(3)CH(2)CF(3), CH(3)CH(2)CH(2)F, CH(3)CHFCH(3), and CH(3)CF(2)CH(3). In an appendix, the method used to assign threshold energies was tested and verified using the combined thermal and chemical activation data for C(2)H(5)Cl, C(2)H(5)F, and CH(3)CF(3).     

Kinetics of the reactions of Cl*(2P(1/2)) and Cl(2P(3/2)) atoms with CH3OH, C2H5OH, n-C3H7OH, and i-C3H7OH at 295 K

The title reactions were studied using laser flash photolysis/laser-induced-fluorescence (FP-LIF) techniques. The two spin-orbit states, Cl*(2P(1/2)) and Cl(2P(3/2)), were detected using LIF at 135.2 and 134.7 nm, respectively. Measured reaction rate constants were as follows (units of cm3 molecule(-1) s(-1)): k(Cl(2P(3/2))+CH3OH) = (5.35 +/- 0.24) x 10(-11), k(Cl(2P(3/2))+C2H5OH) = (9.50 +/- 0.85) x 10(-11), k(Cl(2P(3/2))+n-C3H7OH) = (1.71 +/- 0.11) x 10(-10), and k(Cl(2P(3/2))+i-C3H7OH) = (9.11 +/- 0.60) x 10(-11). Measured rate constants for total removal of Cl*(2P(1/2)) in collisions with CH3OH, C2H5OH, n-C3H7OH, and i-C3H7OH were (1.95 +/- 0.13) x 10(-10), (2.48 +/- 0.18) x 10(-10), (3.13 +/- 0.18) x 10(-10), and (2.84 +/- 0.16) x 10(-10), respectively; quoted errors are two-standard deviations. Although spin-orbit excited Cl*(2P(1/2)) atoms have 2.52 kcal/mol more energy than Cl(2P(3/2)), the rates of chemical reaction of Cl*(2P(1/2)) with CH3OH, C2H5OH, n-C3H7OH, and i-C3H7OH are only 60-90% of the corresponding Cl(2P(3/2)) atom reactions. Under ambient conditions spin-orbit excited Cl* atoms are responsible for 0.5%, 0.5%, 0.4%, and 0.7% of the observed reactivity of thermalized Cl atoms toward CH3OH, C2H5OH, n-C3H7OH, and i-C3H7OH, respectively.     

Photodissociation of Mg+-XCH3 (X=F, Cl, Br, and I) complexes. I. Electronic spectra and dissociation pathways

Photodissociation spectra of Mg+-XCH3 (X=F, Cl, Br, and I) complexes have been measured in the ultraviolet region (225-415 nm). Several fragment ions with and without charge transfer (CT), Mg+, XCH3+, MgX+, MgCH3+, CH3+, and X+, were formed by evaporation (intermolecular bond dissociation) and intracluster reaction (intramolecular bond dissociation) via excited electronic states. Branching ratios of these ions were found to depend both on absorption bands and on halogen atoms. The ground states of the complexes were calculated to have geometries in which the Mg atom lies next to X atom of methyl halide molecules. Positive charges of the complexes are confirmed to be almost localized on Mg. Observed absorption bands were assigned to the transitions of the Mg+2P-2S atomic line perturbed by interactions with methyl halide molecules. Branching ratios of fragment ions can be partly explained by the stability of fragment ions and neutral counterparts. From the excited state potential energy curves along the Mg-X bond distance, dissociation reaction after CT was concluded to proceed predissociatively; potential curve crossings between the initially excited states and repulsive CT states may have a crucial role in the formation of CH3+, XCH3+, and X+. In particular, XCH3+ ions were formed via repulsive CT states having a character of electron excitation from Xnp to Mg+3s.     

G3 and density functional theory investigations of the structures and energies of SF(n)Cl (n=0-5) and their anions

Computations of structures and total energies have been carried out for neutral and anionic SF(n)Cl (n=0-5), using the composite G3 method and density functional theory (DFT) at the B3LYP6-311+G(3df) level. The total energies and zero-point energies have been used here to derive electron affinities, bond dissociation energies, and heats of formation. In addition, vibrational frequencies, polarizabilities, and dipole moments are reported. Results are compared with earlier work for SF(m) (m=1-6) and demonstrate how the relatively weak S-Cl bond and reduced symmetry influence the properties of these molecules and anions. Comparisons are also made between G3 and DFT results for SF(n)Cl. Of particular interest is the alternating pattern of agreement between calculated electron affinity values with n. These calculations also provide critical energetic data needed to understand experimental measurements of electron attachment to SF(5)Cl [Van Doren et al., J. Chem. Phys. 128, 094309 (2008)] for which numerous ion products have been reported in the literature at low electron energy.     

Electronic absorption spectra of C3Cl, C4Cl, and their ions in neon matrices

Electronic absorption spectra of C3Cl, C3Cl+, C3Cl-, C4Cl, and C4Cl+ have been recorded in 6 K neon matrices following mass selection. Ab initio calculations were performed (CCSD(T) and CASSCF) to identify the ground and accessible excited states of each molecule. The estimated excitation energies and transition moments aid the assignment. The absorptions observed for C3Cl are the 5(2)A' <-- X(2)A' and 3(2)A' <-- X(2)A' transitions of the bent isomer and the (2)A1 <-- X(2)B2 transition of the cyclic form in the UV (336.1 nm), visible (428.7 nm), and near-IR (1047 nm) regions, respectively. The band systems for bent C3Cl- (435.2 nm) and linear C3Cl+ (413.2 nm) are both in the visible region and correspond to 2(1)A' <-- X(1)A' and (1)pi <-- X(1)sigma+ type transitions. The C4Cl and C4Cl+ chains are linear, and the band origins of the 2(2)pi <-- X(2)pi and 2(3)pi <-- X(3)pi electronic transitions are at 427.0 and 405.7 nm. The spectral assignments are supported by analysis of the vibrational structure associated with each electronic transition.     

The dissociation dynamics of He...I 35Cl(B,v'=2,3) complexes with varying amounts of internal energy

The He...I (35)Cl intermolecular vibrational levels with n'=0-6 that are bound within the He+ICl(B,v'=3) potential [A. B. McCoy, J. P. Darr, D. S. Boucher, P. R. Winter, M. D. Bradke, and R. A. Loomis, J. Chem. Phys. 120, 2677 (2004)] are identified in laser-induced fluorescence experiments performed at very low temperatures within a supersonic expansion. Comparisons of the positions and intensities of these lines with the excitation spectra, calculated using potential surfaces to describe the interactions between the helium atom and ICl in its ground and excited state, assist in the assignments. Based on these comparisons the excited state potential was rescaled so that the experimental and calculated J'=0 energies agree to within the experimental uncertainties for all but the lowest, n'=0, intermolecular level. Two-laser, action, and pump-probe spectroscopy experiments indicate that the bound He...I (35)Cl(B,v'=3) intermolecular vibrational levels undergo vibrational predissociation forming rotationally excited I (35)Cl(B,v'=2,j') products with distributions that depend upon the initial intermolecular vibrational level excited. Action spectra recorded in the ICl B-X, 2-0 region while monitoring the Deltav=0, I (35)Cl(B,v'=2) channel reveal two additional dissociation mechanisms for the He...I (35)Cl(B,v') excited state complexes: rotational predissociation of discrete metastable states lying slightly above the He+I (35)Cl(B,v'=2) asymptote and direct dissociation that occurs when the linear conformer is excited to the continuum of states above the same asymptote. The rotational predissociation pathway forms I (35)Cl(B,v'=2,j') products in all of the rotational states energetically accessible. The direct dissociation mechanism yields very cold rotational product state distributions; for instance, the average rotational energy in the product state distribution measured when the linear complexes are prepared 20 cm(-1) above the dissociation limit is only 1.51 cm(-1), representing only 7.6% of the available energy.     

Vibrational spectra and structure of CH3Cl:NO complex: IR matrix isolation and DFT study

Infrared spectra of the CH(3)Cl:NO complex isolated in solid neon have been investigated. Most of the vibrational modes of the complex have been detected. The weak interaction between NO and CH(3)Cl in CH(3)Cl:NO is responsible for small shifts of the vibrational mode frequencies of both CH(3)Cl and NO molecules. The measured shifts range between -3.2 and + 3.8 cm(-1). On the basis of DFT calculations, different geometries have been explored for the complex, and it has been shown that the most stable structure is of C(1) symmetry. The calculated frequency shifts match well the experimental data.     

Dissociation dynamics of positive-ion and negative-ion fragments of gaseous and condensed Si(CH(3))(2)Cl(2) via Si 2p, Cl 2p, and Cl 1s core-level excitations

The state-selective positive-ion and negative-ion dissociation pathways of gaseous and condensed Si(CH(3))(2)Cl(2) following Cl 2p, Cl 1s, and Si 2p core-level excitations have been characterized. The excitations to a specific antibonding state (15a(1) (*) state) of gaseous Si(CH(3))(2)Cl(2) at the Cl 2p, Cl 1s, and Si 2p edges produce significant enhancement of fragment ions. This ion enhancement at specific core-excited states correlates closely with the ion kinetic energy distribution. The results deduced from ion kinetic energy distribution are consistent with results of quantum-chemical calculations on Si(CH(3))(2)Cl(2) using the ADF package. The Cl(-) desorption yields for Si(CH(3))(2)Cl(2)Si(100) at approximately 90 K are notably enhanced at the 15a(1) (*) resonance at both Cl 2p and Si 2p edges. The resonant enhancement of Cl(-) yield occurs through the formation of highly excited states of the adsorbed molecules. These results provide insight into the state-selective ionic fragmentation of molecules via core-level excitation.     

Ab initio study of the ground and lower-lying excited electronic states of NiX2 and FeX2 (X=F,Cl, Br,I) molecules

The ground and lower-lying excited electronic states of FeX₂ and NiX₂ (X=F, Cl, Br, I) molecules are systematically investigated by ab initio method at the complete active space self-consistent field (CASSCF) and multiconfigurational quasi-degenerate second-order perturbation (MCQDPT2) levels of theory. It is concluded that the dynamic electron correlation has to be taken into account in the prediction of the properties for such kind of molecules. The equilibrium bond lengths r_e(M–X), force constants and harmonic vibrational frequencies are calculated for the ground and lower-lying excited electronic states. The spin-orbit coupling (SOC) effects are analysed.