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.     

磷炔R-C≡P(R=-BH2,-CH3,-NH2,-OH)及其异构体的稳定性

采用 B3LYP和 CCSD(T)方法对 R-C≡ P(R=-BH2, -CH3,-NH2, -OH)体系进行了理论研究 .结果表明,含 C≡ P三键的异构体 BH2-C≡ P和 CH3-C≡ P在各自的体系中分别是热力学最稳定的结构 .而在 HO-C≡ P和 NH2-C≡ P体系中,热力学最稳定的结构却是 H-P=C=O和含 C≡ N三键的 N≡ C-PH2.动力学理论研究表明,没有相关实验研究的 R-C≡ P(R=-BH2,NH2)体系中共有 5种异构体是动力学稳定的 .在 HO-C≡ P体系的 2种动力学稳定的异构体中, H-P=C=O连接方式的异构体已被实验所证实,而另外一种 HO-C≡ P连接方式的异构体的动力学稳定性较高,实验中可以观察到 .对于 CH3C≡ P体系,研究所预示的 2种动力学稳定的异构体中 CH3-C≡ P已被实验证实,从理论上推测另一种动力学稳定性较高的异构体 HC≡ C-PH2在实验中也可以检测到.     

C59XH(X=N,B)自由基加成区域选择性的理论研究

用半经验的AMl方法,对C59XHCl2n(X=N,B;n=1～2)和C60H2Cl2n(n=1～2)的异构体进行几何构型全优化和振动频率计算,结合密度泛函B3LYP／6—31G^*单点能计算确定各异构体的相对稳定性．对比C59XH(X=N,B)和C60H2的H2加成方式,计算结果表明H2或Cl2加在碳笼官能化部分的邻近位置在能量上都是有利的：C59NH和C59BH自由基多加成物区域选择性的差别可归因于N原子和B原子电子性质的不同;立体效应是导致H2和Cl2加成方式不同的主要原因．     

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.     

C28H4-nCln(n=1~3)与CH4-nCln(n=1~3)的结构和电子光谱的理论研究

用INDO系列方法对C28H3Cl, C28H2Cl2, C28HCl3, CH3Cl, CH2Cl2, CHCl3进行了几何构型优化, C28H3Cl, C28HCl3, CH3Cl, CH3Cl为C3v对称性,C28H2Cl2, CH2Cl2为C2v对称性, 这六个分子的基态都是稳定闭壳层分子, 以此构型为基础计算了上述分子的电子光谱, C28H4-nCln(n=1~3)的电子光谱属于理论预测性质。     

C_(70)R_2(R=OH,CH_3)的结构和电子光谱

INDO方法研究了C70R2（R＝OH，CH3）4种异构体的结构和稳定性，表明1，9－C70（OH）2比7，8－C70（OH）2稳定，两者能量差为38．5kJ／mol，而7，8－C70（CH3）2比1，9－C70（CH3）2能量低23．0kJ／mol．以优化构型为基础，对C70R2（R＝OH，CH3）的电子光谱进行了理论预测．     

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.     

C40X2（X=H,F,Cl,Br）的理论研究

应用密度泛函理论在B3LYP/6-31G*水平上对C40X2(X=H,F,Cl,Br)进行研究.研究结果表明,C40X2(X=H,F,Cl,Br)在热力学上是稳定的,卤化衍生物的稳定性随卤素原子序数的增大而降低,最有利的衍生化方式是1-4加成,1-2与1-4加成的卤化和氢化衍生物在所研究的分子中较为稳定.这些研究有助于理解富勒烯衍生物的衍生化模式.     

Theoretical studies on fullerene C4o′s derivatives C4o X2 (X =H, F, Cl, Br)

应用密度泛函理论在B3LYP/6 31G*水平上对C40X2 (X=H,F,Cl,Br)进行研究.研究结果表明,C40X2 (X=H,F,C1,Br)在热力学上是稳定的,卤化衍生物的稳定性随卤素原子序数的增大而降低,最有利的衍生化方式是1-4加成,1-2与1-4加成的卤化和氢化衍生物在所研究的分子中较为稳定.这些研究有助于理解富勒烯衍生物的衍生化模式.     

C_(59)F_(2n)HN(n=1,2)异构体的结构与稳定性的理论研究

分别用MNDO和AM1两种半经验方法,对C59F2nHN (n = 1, 2) 的异构体进行几何构型全优化,结合频率分析及HF/6-31G单点能计算,确定了各异构体的基态结构及其相对稳定性。计算结果表明,C59HN的F加成物的立体选择性规律与C60的不同,最稳定异构体不是1-2加成物。C59F2HN的最稳定异构体是1-4加成的6, 18-或12, 15-异构体; C59F4HN的最稳定异构体是1-4,1-4加成的6, 18; 12, 15-异构体,其能量远小于其它各异构体的能量。N原子取代碳笼骨架C原子后,改变了碳笼F加成物的立体选择性规律。     

C2H5C60H的加成产物的结构和光谱性质的量子化学研究

用INDO系列方法对C₂H₅C₆₀H的1,2-加成和1,4-加成两种产物异构体的结构进行了理论研究,结果表明1,2-C₂H₅C₆₀H具有Cs对称性,1,4-C₂H₅C₆₀H没有任何对称性,1,2-C₂H₅C₆₀H的总能量比1,4-C₂H₅C₆₀H的低。以此优化构型为基础,计算了两种产物异构体的电子吸收光谱,讨论了其光谱红移的原因,同时对产物的NMR谱进行了探讨。     

A DFT study on the dimerization of C62, H2-C62, and F2-C62

On the basis of calculations using the density functional theory, we show that C(62), a recently synthesized nonclassical fullerene, will presumably undergo dimerization with various isomers at elevated temperatures. This is shown by calculating the dimerization energy and the activation barrier of the dimerization. Eight possible isomers of the dimer were identified, all of which are more stable than the two isolated monomers. The relative stability of various isomers depends upon the kind of C=C bonds within the four-membered carbon ring involved in the dimerization. In addition, similar calculations were performed for the monomers and dimers of H(2)-C(62) and F(2)-C(62). Six isomers were identified for each of the dimers. Although less pronounced than the case of the C(62) dimer, all isomers of the H(2)-C(62) dimer are appreciably more stable than the individual monomers. Although a large steric repulsion due to F atoms significantly reduces the stability of F(2)-C(62) dimer, its two isomers are still more stable than separate monomers.     

Searching for stable hept-C62X2 (X = F, Cl, and Br): structures and stabilities of heptagon-containing C62 halogenated derivatives

To determine the geometries of the most stable hept-C(62)X(2) (X = F, Cl, and Br) isomers, all 967 possible hept-C(62)F(2) isomers have been orderly optimized using AM1, HF/STO-3G, B3LYP/3-21G, and B3LYP/6-31G* methods, and chlorofullerenes and bromofullerenes, which are isostructural with five most stable hept-C(62)F(2) isomers, were regarded as candidates of the most stable isomer, and optimized at the B3LYP/6-31G* level. The results reveal that 2,9- and 9,62-hept-C(62)X(2) (X = F, Cl, and Br) are the two most stable isomers with slight energy difference. The halogenation releases strain energy of hept-C(62), and all halogenated fullerenes are more chemically stable than hept-C(62) with lower E(HOMO) and higher E(LUMO). All five most stable hept-C(62)X(2) (X = F, Cl, and Br) isomers are energetically favorable, and their thermodynamic stability decreases along with the increase of sizes of addends. Only hept-C(62)F(2) isomers show high thermodynamic stability, and they are potentially synthesized in experiments. 59,62-squ-C(62)X(2) (X = F, Cl, and Br) were computed for comparison, and they are found to be more stable than their heptagon-containing isomers.     

Ab Initio calculations of the stabilization energies of the conformational and the structural isomers of C(3)H(7)X where X = F,Cl, and Br

HF, MP2, and B3LYP calculations with different basis sets have been used in the computation of the stabilization energies of C(3)H(7)X isomers, where X is F, Cl, and Br. The experimental stabilization energies of the structural isomers of C(3)H(7)Cl and C(3)H(7)Br have been reproduced via B3LYP calculations. However, the calculated stabilization energies of fluoropropane isomers from their reported enthalpies of formation have been reproduced in all methods of calculations in present work. The experimental relative stabilities of the gauche conformers of 1-fluoro-, 1-chloro-, and 1-bromopropanes have been also reproduced via some of the used calculations in the present work. The effect of the geminal interactions on X atomic charges and on the C-X and C-C bond lengths in halopropane isomers are also discussed.     

Isomeric effects in the gas-phase reactions of dichloroethene, C2H2CL2, with a series of cations

A study of the reactions of a series of gas-phase cations (NH(4)(+), H(3)O(+), SF(3)(+), CF(3)(+), CF(+), SF(5)(+), SF(2)(+), SF(+), CF(2)(+), SF(4)(+), O(2)(+), Xe(+), N(2)O(+), CO(2)(+), Kr(+), CO(+), N(+), N(2)(+), Ar(+), F(+), and Ne(+)) with the three structural isomers of dichloroethene, i.e., 1,1-C(2)H(2)Cl(2), cis-1,2-C(2)H(2)Cl(2), and trans-1,2-C(2)H(2)Cl(2) is reported. The recombination energy (RE) of these ions spans the range of 4.7-21.6 eV. Reaction rate coefficients and product branching ratios have been measured at 298 K in a selected ion flow tube (SIFT). Collisional rate coefficients are calculated by modified average dipole orientation (MADO) theory and compared with experimental data. Thermochemistry and mass balance have been used to predict the most feasible neutral products. Threshold photoelectron-photoion coincidence spectra have also been obtained for the three isomers of C(2)H(2)Cl(2) with photon energies in the range of 10-23 eV. The fragment ion branching ratios have been compared with those of the flow tube study to determine the importance of long-range charge transfer. A strong influence of the isomeric structure of dichloroethene on the products of ion-molecule reactions has been observed for H(3)O(+), CF(3)(+), and CF(+). For 1,1-C(2)H(2)Cl(2) the reaction with H(3)O(+) proceeds at the collisional rate with the only ionic product being 1,1-C(2)H(2)Cl(2)H(+). However, the same reaction yields two more ionic products in the case of cis-1,2- and trans-1,2-C(2)H(2)Cl(2), but only proceeds with 14% and 18% efficiency, respectively. The CF(3)(+) reaction proceeds with 56-80% efficiency, the only ionic product for 1,1-C(2)H(2)Cl(2) being C(2)H(2)Cl(+) formed via Cl(-) abstraction, whereas the only ionic product for both 1,2-isomers is CHCl(2)(+) corresponding to a breaking of the C=C double bond. Less profound isomeric effects, but still resulting in different products for 1,1- and 1,2-C(2)H(2)Cl(2) isomers, have been found in the reactions of SF(+), CO(2)(+), CO(+), N(2)(+), and Ar(+). Although these five ions have REs above the ionization energy (IE) of any of the C(2)H(2)Cl(2) isomers, and hence the threshold for long-range charge transfer, the results suggest that the formation of a collision complex at short range between these ions and C(2)H(2)Cl(2) is responsible for the observed effects.     

Search for more stable C58X18 isomers: stabilities and electronic properties of seven-membered ring C58X18 fullerene derivatives (X = H, F, and Cl)

Stimulated by recent preparation and characterization of the first C58F18 fullerene derivative, with a heptagon in the framework (Science, 2005, 309, 278), we have performed systematic density functional studies on the stabilities and electronic properties of two different structures C58X18 (A) and C58X18 (B), where X = H, F, and Cl. The large energy gaps between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals (between 2.64 and 3.45 eV) and the aromatic character (with nucleus independent chemical shifts from -10.0 to -13.9 ppm) of C58X18 (A) and C58X18 (B) indicate that they possess high stabilities. Further investigations show that the heats of formation of C58X18 fullerene derivatives are highly exothermic, suggesting that adding nine X2's releases much of the strain of pure C58 fullerene and leads to stabilities of the derivatives. Lower in energy and stronger in aromatic character than C58F18 (B), which has been experimentally characterized, C58F18 (A) should also be isolated. In addition, C58F18 and C58Cl18 are predicted to possess large electron affinities, especially for C58F18 (B) and C58Cl18 (B) with values of 3.00 and 3.06 eV, respectively, even larger than that (2.50 eV) of C60F18. Hence, C58F18 and C58Cl18 can serve as good electron-acceptors with possible photonic/photovoltaic application. The IR spectra of C58X18 are simulated to facilitate identification of different isomers experimentally. In addition, the electronic spectra and second-order hyperpolarizabilities of C58X18 are predicted by ZINDO and sum-over-states model. With the addition of 9X2, both the static and frequency-dependent second-order hyperopolarizabilities of C58X18 greatly decrease compared to those of C58.     

The homologous series of 1,1'-ferrocenylenebisdihalophosphanes (C5H4PX2)2Fe (X = F, Cl, Br, I): precursors for the first metallocene bridged bisphosphaalkene

A facile synthetic access to the homologous series of 1,1'-ferrocenylene bisdihalophosphanes Fc'(PX2)2 (X = F, Cl, Br, I; Fc' = 1,1'-ferrocenediyl = ferrocenylene = -C5H4FeC5H4-) is reported. The 31P NMR spectroscopic data of this series suggest a similar electronic interaction of the -PX(2) unit with the ferrocene system as in monofunctional ferrocenyldihalophosphanes. Crystal structures for Fc'(PCl2)2 and Fc'(PBr2)2 reveal that the nature of the halogen atom within the phosphane unit strongly influences the twist angle of the ferrocene system, while leaving the other structural parameters mostly unaffected. Based on these bisdihalophosphanes, a synthetic access to the first metallocene bridged bisphosphaalkene ((C5H4P=C(t-Bu)OTMS)2Fe) is reported in which the tert-butyl substituents provide sufficient steric pressure to control the E/Z isomeric ratio which leads to the almost exclusive formation of the most stable Z,Z isomer out of the three possible isomers.     

氯代甲苯异构体双电荷离子电子捕获诱导解离谱研究

研究了４种Ｃ７Ｈ７Ｃｌ异构体在７０ｅＶ电子轰击下产生的［Ｃ７Ｈ７Ｃｌ］＾２＋、［Ｃ７Ｈ６Ｃｌ］＾２＋．和［Ｃ７Ｈ５Ｃｌ］＾２＋ ３种双电荷离子的电子捕获诱导解离（ＥＣＩＤ）反应。分子离子的ＥＣＩＤ反应明显的邻位效应，表明其结构仍保持中性分子的结构特征；而由各异构体产生的［Ｃ７Ｈ６Ｃｌ］＾２＋．和［Ｃ７Ｈ５Ｃｌ］＾２＋离子异构化成同一结构。３种双电荷离子ＥＣＩＤ反应的产物与离子所带电子的奇偶性有关，