Structures and bonding situation of Pb2X2 (X?=?H, F, Cl, Br and I)

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.     

Vibrational study of diphenylphosphorus halides Ph2PX (X  Cl,Br, I)

The Raman and i.r. spectra of diphenylphosphorus halides, Ph₂PX (X  Cl, Br, I), have been measured and concerted assignments have been made confirmed by an approximate normal coordinate analysis for the skeletal vibrations of Ph₂PCl using a three mass model for the phenyl group.     

Schwingungsspektren und Normalkoordinatenanalyse von CF3-Verbindungen—XXIV. IR- und Raman-Spektren der Isobutane (CF3)3CX (X = F,Cl, Br,J)

The i.r. and Raman spectra of the isobutane derivatives (CF₃)₃CX, X = F, Cl, Br and I, have been recorded. The spectra are assigned for C_3ν symmetry, but evidence for lower symmetry conformation of the CF₃ groups is observed. While the fluorine derivative exhibits an individual spectrum, the spectra of the heavier compounds are quite similar and related to those of the carbon tetrahalides.     

Substituent effects on the compounds CX1X2•− (X1, X2 = H, F, Cl, Br, I) from theoretical investigation

The electronic and molecular structures of mono- and dihalocarbene anions constructed by model CX¹X^2?? (X¹, X² = H, F, Cl, Br, I), as well as the corresponding carbenes CX¹X² and analogous silicon-anions SiX¹X^2??, 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.     

Theoretical study on tetranuclear boron clusters: B4X4 (X = H, F, Cl, Br, I)

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.     

Photoelectron Spectroscopy and Structures of X−⋅⋅⋅CH2O (X=F,Cl, Br,I) Complexes

A combined experimental and theoretical approach has been used to investigate X⁻⋅⋅⋅CH₂O (X=F, Cl, Br, I) complexes in the gas phase. Photoelectron spectroscopy, in tandem with time-of-flight mass spectrometry, has been used to determine electron binding energies for the Cl⁻⋅⋅⋅CH₂O, Br⁻⋅⋅⋅CH₂O, and I⁻⋅⋅⋅CH₂O species. Additionally, high-level CCSD(T) calculations found a C_2v minimum for these three anion complexes, with predicted electron detachment energies in excellent agreement with the experimental photoelectron spectra. F⁻⋅⋅⋅CH₂O was also studied theoretically, with a C_s hydrogen-bonded complex found to be the global minimum. Calculations extended to neutral X⋅⋅⋅CH₂O complexes, with the results of potential interest to atmospheric CH₂O chemistry.     

LiY+NH2X(Y=F,Cl,Br,Br;X=F)反应机理的计算研究

一百多年来,无论从实验还是理论上,气相中碳原子上SN2的反应机理都已经得到了广泛的深入研究.近二十几年来,杂原子上的亲核取代反应由于其在生物有机及在人体代谢过程中所起的重要作用而逐渐引起人们的关注.氮原子上的SN2反应是近年来的研究热点,但其中的亲核试剂仅局限于阴离子[1].本文将研究对象扩展到离子对亲核取代反应[2].我们在B3LYP/6-311+G(d,p)水平上讨论了气相中LiY+NH2X(Y=F,Cl,Br,I;X=F)的反应机理,希望能为实验化学家提供有价值的信息.     

An MP2 study on pre-reactive complexes (CH_2)_2O … XY (X,Y = H,F,Cl,Br,I)

The structures, energies, atomic chaiges and IR spectra of complexes (CH2)2O…XY (X, Y = H, F, Cl, Br, and I) have been examined by means of ab initio molecular orbital theory at the second-order level of Moller-Plesset perturbation correction. It is found that the hydrogen bond O…H-X is non-linear. The attraction between X and the H atoms in oxirane ring causes O…H-X bond bending. The hydrogen bond slighdy weakens the bond strength of C-O, and leads the bending and stretching mode of IR to shift to the red. The calculation results show that there is no evidence of a significant extent of proton transfer to give (CH2)2OH …X- in the isolated complexes.     

C56X10(X=F,Cl, Br,I)的结构稳定性和电子性质

采用密度泛函理论(DFT)中的广义梯度近似(GGA)方法对C56X10(X=F, Cl, Br, I)的结构稳定性和电子性质进行了计算研究. 结构稳定性计算表明: 对于C56X10(X=F, Cl, Br, I), 能隙、反应热、最大振动频率和最小振动频率都随着X原子序数的增加而减小, 表明C56X10(X=F, Cl, Br, I)的稳定性随着X原子序数的增加而逐渐降低, 其中C56F10最为稳定. 前人在实验上已成功合成出C56Cl10, 因此, 我们推测C56F10有望在实验上成功合成. 前线轨道计算发现, C56相邻的五边形公共顶点以及两个六边形-五边形-六边形公共顶点是笼子中化学活性最强的部位, 有利于卤族元素的外部吸附. 此外, 计算结果还显示, C56X10(X=F, Cl, Br, I)的电负性随着X原子序数的增大而逐渐减弱, C—X基团的电负性因位置的不同而不同.     

Schwingungsspektren und Normalkoordinatenanalyse von CF3-Verbindungen—XXV. IR- und Raman-Spektren von (CF3)3CH und (CF3)3CD. Normalkoordinatenanalyse der Verbindungen (CF3)3CX(X = H,D, F,Cl, Br,J)

The gas phase i.r. spectra and liquid phase Raman spectra of the isobutane derivatives (CF₃)₃CH and (CF₃)₃CD have been recorded and assigned for C_3ν symmetry. A normal coordinate analysis employing the LSFF principle has been performed for a series of (CF₃)₃CX compounds (X = H, D, F, Cl, Br, I); the force constants are compared with those of other (CF₃)_nCX_4−n compounds. Group vibrations are more pronounced for the isobutanes than for the corresponding propanes (CF₃)₂CX₂.     

Pressure-induced formation of molecular B2X4(μ-X)2 (X = Cl, Br, I) species

Boron(III) halides (BX(3), where X = F, Cl, Br, I) at ambient pressure conditions exist as strictly monomeric, trigonal-planar molecules. Using correlated ab initio calculations, the three heavier halides (X = Cl, Br, I) are shown to possess B(2)X(4)(μ-X)(2) local minima, isostructural with the diborane molecule. The calculated dissociation barrier of the B(2)I(4)(μ-I)(2) species [≈14 kJ/mol with CCSD(T)/cc-pVTZ] may be high enough to allow cryogenic isolation. The remaining dimer structures are more labile, with dissociation barriers of less than 6 kJ/mol. All three dimer species may be stabilized by application of external pressure. Periodic density functional theory calculations predict a new dimer-based P1 solid, which becomes more stable than the P6(3)/m monomer-derived solids at 5 (X = I) to 15 (X = Cl) GPa. Metadynamics simulations suggest that B(2)X(4)(μ-X)(2)-based solids are the kinetically preferred product of pressurization of the P6(3)/m solid.     

C70X2(X=H,F, Cl)的稳定性和电子光谱

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。     

C_(80)X_(12)(X=H,F,Cl,Br)的结构和稳定性

为了考察勒烯衍生物结构与稳定性关系,采用密度泛函理论方法对C80X12(X=H,F,Cl,Br)进行了系统计算究.结表明,在C80X12(X=H,F)异构体中,最低能量异构体都违反五元环分离规则.然而,在C80X12(X=Cl,Br)异构体中,最低能量异构体都满足五元环分离规则.由于van der Waals半径较小,H或F加成到碳笼上时外部原子之间排斥作用小,因此在其优结构中,H或F优先加成到2个五元环共用碳原子上.相反,对于氯化、溴化勒烯,为了避免外部加成原子之间在重空间排斥作用,其优结构中Cl或Br优先加成到1,4-位点上.计算结还显,氢化、卤化反应热(C80+6X2→C80X12)遵循如下顺序,即C80F12>C80Cl12>C80H12>C80Br12.这些结表明勒烯衍生物稳定性和衍生化模与加成原子尺和电性有关.     

Vibrational spectra of icosabedral closoborate anions B12X2−12 (X = H,D, Cl,Br, I)

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 I_h point symmetry group. The changes in the spectra of the solid salts due to the crystal field are revealed.     

Ph3PAuX和Ph3AsAuX(X=Cl,Br)的最低三重激发态

分子水平上的激发态理论研究能够用来解释分子材料的多色发光机理. 采用单组态相互作用方法, 计算研究了四种二配位的Au(I)配合物Ph3PAuCl, Ph3PAuBr, Ph3AsAuCl和Ph3AsAuBr的分子结构限制的三重激发态(T1a)和分子结构松弛的三重激发态(T1b)的分子结构与光物理性质. 由于θ(PAuX)/θ(AsAuX)从180°扭曲到120°左右, T1b态的能量在单线态组态相互作用(CIS)水平上降低了0.805-1.124 eV, 在密度泛函理论(DFT)水平上降低了0.820-0.947 eV. 自然键轨道电荷布居数分析表明, 在T1a态中两个单电子主要分布在一个苯基上, 而在T1b态中两个单电子分布在PAuX/AsAuX 上. 因此, 在晶体中观察到的较高能磷光归属于T1a态的苯基之间的3π*→1π电子跃迁, 而较低能磷光主要起源于T1b态的Au 的3σ*→1σ电子跃迁.     

The HOX⋯SO2 (X=F,Cl, Br,I) Binary Complexes: Implications for Atmospheric Chemistry

Sulfur dioxide and hypohalous acids (HOX, X=F, Cl, Br, I) are ubiquitous molecules in the atmosphere that are central to important processes like seasonal ozone depletion, acid rain, and cloud nucleation. We present the first theoretical examination of the HOX⋯SO₂ binary complexes and the associated trends due to halogen substitution. Reliable geometries were optimized at the CCSD(T)/aug-cc-pV(T+d)Z level of theory for HOF and HOCl complexes. The HOBr and HOI complexes were optimized at the CCSD(T)/aug-cc-pV(D+d)Z level of theory with the exception of the Br and I atoms which were modeled with an aug-cc-pwCVDZ-PP pseudopotential. 27 HOX⋯SO₂ complexes were characterized and the focal point method was employed to produce CCSDT(Q)/CBS interaction energies. Natural Bond Orbital analysis and Symmetry Adapted Perturbation Theory were used to classify the nature of each principle interaction. The interaction energies of all HOX⋯SO₂ complexes in this study ranged from 1.35 to 3.81 kcal mol⁻¹. The single-interaction hydrogen bonded complexes spanned a range of 2.62 to 3.07 kcal mol⁻¹, while the single-interaction halogen bonded complexes were far more sensitive to halogen substitution ranging from 1.35 to 3.06 kcal mol⁻¹, indicating that the two types of interactions are extremely competitive for heavier halogens. Our results provide insight into the interactions between HOX and SO₂ which may guide further research of related systems.     

Theoretical study of X + H2 → XH + H and reverse reactions (X = F,Cl, Br,I) using a new empirical potential energy surface

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.     

Ag@AgX(X=Cl,Br,I)及其复合物光催化剂的研究进展

综述了具有表面等离子体共振效应的光催化剂Ag@AgX(X=Cl,Br,I)及其与TiO2、BiOX、BiVO4、ZnO等复合物的光催化机理、应用等方面的进展,并展望了Ag@AgX(X=Cl,Br,I)及其复合物未来的发展方向和研究内容。     

CH2X(X=H,F,Cl)与臭氧反应机理的量子化学研究

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.     

KINETIC STUDIES OF LEWIS BASE ADDITION TO CpFe(CO)(η3-CH2C6H4-p-X); X = OMe,Me, H,F, Cl,Br

Abstract

Kinetic studies illuminate details of the reaction of photoproduced CpFe(CO)(η³-CH₂C₆H₅) with two electron Lewis bases. Rate constants of 151(10)M^?1s^?1 for CO back reaction and between 440 and 3200 M^?1s^?1 for reaction with various phosphine nucleophiles were recorded. Linear free energy analysis quantifies the stereoelectronic effect of the nucleophile. Variation of the para-substituent on the benzyl group demonstrates that an electron rich benzyl group impedes reaction. The effect of ancillary ligands was seen by substitution of C₅Me₅ for C₅H₅. The large, electron rich C₅Me₅ speeds up CO substitution but slows down PPh₃ substitution. Mechanistic clues were obtained from Eyring plots for reaction of CpFe(CO)(η³-CH₂C₆H₅) with 4 different phosphines. Examination of the measured enthalpy and entropy barriers suggests a stepwise reaction mechanism.