HCHO+X(X=F、Cl、Br)的反应机理

采用CCSD/6-311++G(d,p)//B3LYP/6-311++G(d,p)方法研究了HCHO与卤素原子X(X=F、Cl、Br)的反应机理. 计算结果表明, 卤素原子X(X=F、Cl、Br)主要通过直接提取HCHO中的H原子生成HCO+HX(X=F、Cl、Br). 另外还可以生成稳定的中间体, 中间体再通过卤原子夺氢和氢原子直接解离两个反应通道分别生成HCO+HX(X=F、Cl、Br)和H+XCHO(X=F、Cl、Br). 其中卤原子夺氢通道为主反应通道, HCO和HX(X=F、Cl、Br)为主要的反应产物; 且三个反应的活化能均较低, 说明此类反应很容易进行, 计算结果与实验结果符合很好. 电子密度拓扑分析显示, 在HCHO+X反应通道(b)中出现了T型结构过渡态, 结构过渡态(STS)位于能量过渡态(ETS)之后. 并且按F、Cl、Br的顺序, 结构过渡态出现得越来越晚.     

Topological characteristics of electron density distribution in SSXY --> XSSY (X or Y = F, Cl, Br, I) isomerization reactions

The reactions of SSXY to XSSY (X or Y = F, Cl, Br, I) have been studied at B3LYP/6-311++G(2df) and MP2/6-311++G(2df) levels based on B3LYP/6-311++G(2df) optimized geometries. There are two pathways (X or Y atom transferring) for each reaction of SSXY to XSSY(X or Y = F, Cl, Br, I). The "Atoms in Molecules" theory has been applied to analyze the topological characteristics of electron density distribution along the reaction path. (a) The S-S-X or S-S-Y ring structure transition region (STR) is contributed to S(1)-X or S(1)-Y bond formation and S(2)-X or S(2)-Y bond annihilation. The STR and structure transition state (STS) are defined. (b) Comparing the two pathways of each SSXY --> XSSY (X, Y = F, Cl, Br, I) reaction, X or Y atom transferring, the broader the STR is, the later the STS appears, and the pathway is easier. (c) When X linked to the same S site of a three-member ring (S-S-F, S-S-Cl, S-S-Br, or S-S-I), the ring STR becomes broader and the STS appears later according to the sequence of X = F, Cl, Br, and I. And in these cases, for exothermic reactions, the higher the DeltaE(P-->TS1) is, the broader the STR is and the later the STS appears. (d) When the same Y atom linked to different three-member-ring S-S-X, the STR becomes broader and the STS appears later according to the sequence of X = F, Cl, Br, and I in the ring. And in these cases, for exothermic reactions, the lower the DeltaE(P-->TS2) is, the broader the STR is and the later the STS appears.     

Halogen-hydride interaction between Z-X (Z = CN, NC; X = F, Cl, Br) and H-Mg-Y (Y = H, F, Cl, Br, CH3)

Halogen-hydride interactions between Z-X (Z = CN, NC and X = F, Cl, Br) as halogen donor and H-Mg-Y (Y = H, F, Cl, Br, CH(3)) as electron donor have been investigated through the use of Becke three-parameter hybrid exchange with Lee-Yang-Parr correlation (B3LYP), second-order M?ller-Plesset perturbation theory (MP2), and coupled-cluster single and double excitation (with triple excitations) [CCSD(T)] approaches. Geometry changes during the halogen-hydride interaction are accompanied by a mutual polarization of both partners with some charge transfer occurring from the electron donor subunit. Interaction energies computed at MP2 level vary from -1.23 to -2.99 kJ/mol for Z-F···H-Mg-Y complexes, indicating that the fluorine interactions are relatively very weak but not negligible. Instead, for chlorine- and bromine-containing complexes the interaction energies span from -5.78 to a maximum of -26.42 kJ/mol, which intimate that the interactions are comparable to conventional hydrogen bonding. Moreover, the calculated interaction energy was found to increase in magnitude with increasing positive electrostatic potential on the extension of Z-X bond. Analysis of geometric, vibrational frequency shift and the interaction energies indicates that, depending on the halogen, CN-X···H interactions are about 1.3-2.0 times stronger than NC-X···H interactions in which the halogen bonds to carbon. We also identified a clear dependence of the halogen-hydride bond strength on the electron-donating or -withdrawing effect of the substituent in the H-Mg-Y subunits. Furthermore, the electronic and structural properties of the resulting complexes have been unveiled by means of the atoms in molecules (AIM) and natural bond orbital (NBO) analyses. Finally, several correlative relationships between interaction energies and various properties such as binding distance, frequency shift, molecular electrostatic potential, and intermolecular density at bond critical point have been checked for all studied systems.     

Competition between halogen bond and hydrogen bond in complexes of superalkali Li3S and halogenated acetylene XCCH (X = F,Cl, Br,and I)

Complexes of superalkali Li₃S and XCCH (X = F, Cl, Br, and I) have been studied with theoretical calculations at the MP2/aug‐cc‐pVTZ level. Three types of structures are found: (A) the X atom combines with the S atom through a halogen bond; (B) the X atom interacts with the π electron of Li₃S by a π halogen bond; (C) the H atom combines with the S atom through a hydrogen bond. For A and B, a heavier halogen atom makes the interaction stronger, while for C, the change of interaction energy is not obvious, showing a small dependence on the nature of the X atom in HCCX. A is more stable than B and their difference in stability decreases as X varies from Cl to I. For the F and Cl complexes, A is weaker than C, however, the former is stronger than the latter in the Br and I complexes. The above three types of interactions have been analyzed by means of electron localization function, electron density difference, and energy decomposition, and the results show that they have similar nature and features with conventional interactions. © 2014 Wiley Periodicals, Inc.     

C_(56)X_(10)(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.     

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.     

Coordination Polyhedra OsXn(X = F, Cl, Br, I) in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analysis of compounds containing complexes [Os _a X _b ] ^z–(X = F, Cl, Br, I). Atoms of Os(V) at X = F and Cl, of Os(IV) at X = Cl, Br, and of Os(III) at X = Br were found to exhibit a coordination number of 6 with respect to the halogen atoms and to form OsX₆octahedra. The coordination polyhedra of Os(III) for X = Cl, I are square pyramids OsX₄. Each Os(III) atom forms one Os–Os bond; as a consequence, the OsBr₆octahedra share a face in forming Os₂Br^3– ₉complexes, while the OsX₄pyramids (X = Cl, I) dimerize to produce [X₄Os–OsX₄]^2–ions. The influence of the valence state of the Os atoms and of the nature of the halogen atoms on the composition and structure of the complexes formed and some characteristics of the coordination sphere of Os were considered.     

Electronic Structure and Properties of Trihalogen Cations X(3)(+) and XY(2)(+) (X, Y = F, Cl, Br, I)

Electronic structures, charge distributions, geometries, valence force constants, and vibrational frequencies of the homoatomic clusters F(3)(+), Cl(3)(+), Br(3)(+), and I(3)(+) and of the heteroatomic clusters ClF(2)(+), BrF(2)(+), IF(2)(+), BrCl(2)(+), ICl(2)(+), and IBr(2)(+) were determined. The self-consistent field approach extended by MP2-correlation energy or density-functional corrections was applied using various basis sets. It was found that d- and f-type polarization functions play a crucial role as in some other halogen compounds. The MP2 approach yields the most satisfactory results. The effect of the crystalline environment surrounding the Cl(3)(+), Br(3)(+), and I(3)(+) species is successfully simulated by a Madelung potential. Frequencies calculated in the crystal field are in reasonable agreement with the more reliable ones among the experimental results. Coupling force constants were determined. They are not consistent with some empirical rules. Bonding and charge distributions of the formally mixed-valence systems X(+)Y(2)(0) are discussed. X(+) behaves like a divalent chalcogen with high electronegativity. Each of the X(+)-Y bonds in XY(2)(+) is very similar to the bond in X-Y. We predict the experimentally unknown F(3)(+) to be stable in vacuum but not in the solid state. Structures and frequencies of XY(2)(+) species, which are as yet unknown, are also predicted.     

Density functional theory study on the reactions of X− with CH3SY (X,Y = F,Cl, Br,I)

Gas‐phase anionic reactions X^? + CH₃SY (X, Y = F, Cl, Br, I) have been investigated at the level of B3LYP/6‐311+G (2df,p). Results show that the potential energy surface (PES) of gas‐phase reactions X^? + CH₃SY (X, Y = Cl, Br, I) has a quadruple‐well structure, indicating an addition–elimination (A–E) pathway. The fluorine behaves differently in many respects from the other halogens and the reactions F^? + CH₃SY (Y = F, Cl, Br, I) correspond to deprotonation instead of substitution. The gas‐phase reactions X^? + CH₃SF (X = Cl, Br, I), however, follow an A–E pathway other than the last two out going steps (COM2 and PR) that proceeds via a deprotonation. The polarizable continuum model (PCM) has been used to evaluate the solvent effects on the energetics of the reactions X^? + CH₃SY (X, Y = Cl, Br, I). The PES is predicted to be unimodal in the solvents of high polarity. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Electronic structures and electron detachment energies of halogen substituted acetate anions, XCH2COO- (X=F,Cl,Br)

The electronic structures and the halogen inductive effects on the acetate anion were investigated in XCH2COO- (X=F,Cl,Br) by photoelectron spectroscopy (PES) and ab initio calculations. The PES spectra indicated that the electron binding energies increased in the order of FCl>Br. These systematic changes of detachment energy and IPs were explained by examining the charge redistributions upon detaching electrons.     

Structures and electronic properties of Al7x0,- and Al13 X1,2,12- clusters with X=F, Cl, and Br

The structures, binding energies, and electronic properties for Al7X, Al7X-, Al13X-, Al13X2-, and Al13X12- (X = F, Cl, Br) were studied at the B3LYP/6-311+G(2d,p) level. Among the systems studied, Al7 and Al13 clusters in Al7X and Al13X- reveal alkali-like and halogen-like superatom characters, respectively. Al7 can bind with one halogen atom to form a salt-like compound as Al7+delta-X-delta. Al13- can combine with one halogen atom to form a diatomic halogen anion Al13X-. However, when adding more halogens, the superatom structure would be destroyed, resulting in low-symmetry compounds with the center Al atom moving toward the cluster surface. The structures of Al13X1,2,12- (X = F, Cl, Br) are similar to those of X = I; however, their binding energies and electron structures are much different. In addition, the analyses of the calculated NBO charges show that Cl and Br have similar properties, but much different from F, when interacting with the Al clusters. The Al-Cl and Al-Br bonds have more covalent character in Al7X and Al13X2,12-, in contrast to the corresponding Al-F bond, which has prominent ionic character.     

苯-卤素(X2, X=F, Cl, Br, I)相互作用本质的对称性匹配微扰理论研究

在MP2水平下对被定义为"电荷转移复合物(CTC)"的苯(C6H6)-卤素分子X2(X＝F, Cl, Br, I)相互作用体系进行了量子化学研究. 在优化所得C6H6-X2(X＝F, Cl, Br, I)复合物的平衡几何结构中, 卤素分子X2接近垂直指向苯环上碳-碳双键的中心. 自然键轨道(NBO)分析结果表明, 苯-卤素体系中电荷转移的数量很少. 对称性匹配微扰理论(Symmetry-adapted perturbation theory, SAPT) 能量分解结果显示, 在4个复合物体系中, 静电作用的贡献相对较小(只占总吸引作用的20%左右), 对于C6H6-F2体系, 色散作用是其主要吸引作用, 对于C6H6-Cl2, C6H6-Br2和C6H6-I2 体系, 诱导作用则是其主要的吸引作用, 从F到I, 色散作用逐渐减弱, 诱导作用逐渐增强, 表明在电子相关水平上将苯-卤素体系称为"电荷转移复合物"的说法并不确切.     

Ionization energies of LinX (n = 2, 3; X = Cl, Br, I) molecules

Molecules of Li(n)X (n = 2, 3; X = Cl, Br, I) were examined with a magnetic sector mass spectrometer by surface ionization using a triple rhenium filament impregnated with fullerene (C60). The ionization energies obtained for Li(2)Cl, Li(2)Br and Li(2)I molecules are 3.8 +/- 0.1, 3.9 +/- 0.1 and 4.0 +/- 0.1 eV, respectively. The first ionization energy of Li(2)Cl is documented, while there are no literature data for the ionization energies of Li(2)Br and Li(2)I. The molecules of Li(3)Cl, Li(3)Br and Li(3)I were detected experimentally for the first time with ionization energies of 4.0 +/- 0.1, 4.1 +/- 0.1 and 4.1 +/- 0.1 eV, respectively. The ionization energies of Li(n)X (n = 2, 3; X = Cl, Br, I) are in correlation with the theoretical prediction of their hyperlithiated configurations.     

On the molecular structure of X-CF3 molecules (X = Cl,Br, I)

The average molecular structures of X-CF₃, molecules (X = Cl, Br, I) have been determined by combined use of electron diffraction and microwave data. Including results for X = H and X = F a strict correlation between C-F bond length and the electronegativity of the X atom is observed. This correlation can be nicely understood in terms of the electron distribution calculated in the CNDO/2 approximation. It is also observed that the change in the C-X bond length with substitution of the CF₃-group by a CH₃-group is strictly correlated with the electronegativity of the X atom.     

Application of the FAKE molecular-orbital method to diatomic molecules XY (X,Y = H,F, Cl,Br, I)

Theoretical Chemistry Accounts - The FAKE (fast, accurate kinetic energy) method of semiempirical molecular orbital calculation is applied to diatomic molecules XY (X, Y= H, F, Cl, Br, I). The...     

Structures and electron attachment properties of halomethanes (CX(n)Y(m), X=H, F; Y=Cl, Br, I; n=0,4; m=4-n)

Theoretical studies of structures of neutral molecules and their anions as well as dissociative electron attachment properties are presented for the halomethanes of general formula CX(n) Y(m); X=H, F; Y=Cl, Br, I; n=0,4; m=4-n. The dissociative electron attachment seems to be the primary process resulting in toxicity of these species. The halomethane anions containing hydrogens are formed as radical-anion adducts. When H is replaced by F, these species become true sigma* radicals. The electron affinities are computed using a variety of computational techniques including the four-order M?ller-Plesset (MP4) technique that included 250 basis functions. It is challenging to compare the computed results with experiment due to dearth of experimental data and uncertainties in the existing experimental data. Thus in certain cases larger differences are found between the computed and experimental values.     

Theoretical study on intermolecular interactions between furan and dihalogen molecules XY(X,Y=F,Cl,Br)

Equilibrium geometries, interaction energies, atomic charge, and charge transfer for the intermolecular interactions between furan and dihalogen molecules XY(X; Y=F,Cl,Br) were studied at the MP2aug-cc-pVDZ level. Three types of geometry are observed in these interactions: the pi-type geometry (I), in which the XY lies above the furan ring and almost perpendicularly to the C4-C5 bond of furan; the sigma-type geometry (II), where the X atom is pointed toward the nonbonding electron pair (n pair) of oxygen atom in furan; and the chi-type geometry (III), describing a blueshift hydrogen bond formed between the hydrogen atom of furan and dihalogen molecules XY. The calculated interaction energies show that the pi-type structures are more stable than the corresponding sigma-type and chi-type structures. To study the nature of the intermolecular interactions, an energy decomposition analysis was carried out and the results indicate that both the pi-type and sigma-type interactions are dominantly inductive energy in nature, while dispersion energy governs the chi-type interactions.     

Some measures for making halogen bonds stronger than hydrogen bonds in H2CS-HOX (X = F, Cl, and Br) complexes

The properties and applications of halogen bonds are dependent greatly on their strength. In this paper, we suggested some measures for enhancing the strength of the halogen bond relative to the hydrogen bond in the H(2)CS-HOX (X = F, Cl, and Br) system by means of quantum chemical calculations. It has been shown that with comparison to H(2)CO, the S electron donor in H(2)CS results in a smaller difference in strength for the Cl halogen bond and the corresponding hydrogen bond, and the Br halogen bond is even stronger than the hydrogen bond. The Li atom in LiHCS and methyl group in MeHCS cause an increase in the strength of halogen bonding and hydrogen bonding, but the former makes the halogen bond stronger and the latter makes the hydrogen bond stronger. In solvents, the halogen bond in the Br system is strong enough to compete with the hydrogen bond. The interaction nature and properties in these complexes have been analyzed with the natural bond orbital theory.     

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.     

卤代氰基卡宾自由基XCCN(X=F,Cl,Br)的理论研究

在C_s对称性和ANO-S基组下, 使用全活化空间自洽场方法(CASSCF), 研究了卤代氰基卡宾自由基及其阴离子的低能电子激发态性质. 为了进一步考虑电子的动态相关效应,采用多组态二级微扰理论(CASPT2)获得更加精确的能量值. 计算结果表明, XCCN的基态是三重态. 单重态和三重态的能隙差ΔE_S-T(kJ/mol): 7.4(FCCN)<13.4(ClCCN)<16.6(BrCCN). 计算得到, XCCN(X=F, Cl, Br)最低垂直激发能分别为408.3, 385.4和 345.2 kJ/mol, 这归因于π(a′) →n_xy 的电子跃迁; XCCN的电子亲和势分别为235.7, 233.0和 237.2 kJ/mol, 与HCCN相比, 其电子亲和势变大.