Theoretical studies on structures and UV-Vis spectra of C70O

Systematic studies on eight isomers of C₇₀O were performed by means of INDO methods. It has been indicated that the O atom is mainly added to the C₁-C₂ or C₃-C₃ bond and an epoxide feature with C_s symmetry is formed. Based on the optimized geometries, the UV-Vis spectra were calculated. It has been found that the main peaks of C₇₀O resemble those of C₇₀ and the characteristic absorptions beyond 460 nm are produced, which is in agreement with the experimental results. Theoretical assignments about the absorptions were canied out and the reason for the red-shift of the absorptions was discussed. C₇₀O is probably composed of four isomers according to the calculated results. Project supported by the National Natural Science Foundation of China.     

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。     

C70NH的结构和光谱的理论研究

摘要本文用INDO系列方法对C70NH的8种异构体构型进行计算，结果表明最稳定的构型是N原子加在C3-C3键和C4-C4键上形成具有CS对称性且不开环的三元环结构。研究了这两种最稳定构型的电荷分布，指出了C70NH的8种构型的^13CNMR谱。进行了UV-Vis光谱计算，结果表明C70NH主峰与C70一致，并在500nm以上产生特征吸收峰；C70NH与C70。相比将发生UV谱带红移的现象，同时讨论了谱带红移的原因。     

异质富勒烯C76BN的UV和IR光谱研究

Twenty-tow possible isomers for C76BN were studied by INDO methods. The two most stable geometries are 52,53-C76BN and 29,28-C76BN, in which boron and nitrogen atoms are connected with each other and located at the 6/6 bond near the longest axis of C78(C2v). Electronic spectra of C76BN were investigated with INDO/SCI method. UV absorptions of C76BN are red-shifted compared with those of C78(C2v). The structures and IR spectra for the four stable isomers of C76BN were calculated by AM1 method. It was indicated that the substitution of the BN unit weakens the conjugation of carbon atoms, leading to the decrease of IR frequencies.     

Stabilities and Electronic Spectra for C78O2 Isomers

1 INTRODUCTION Functional derivatives of fullerenes have aroused chemists’ interest and monofunctional products are accompanied by difunctional derivatives[1～3]. Diede- rich[1] prepared and detected C70O2 by the FAB mass spectrum. Kalsbeck[2] synthesized C60On (n = 1～4) by electrochemical oxidation of C60. Wood[3] investi- gated photolysis of a crude fullerene mixture and obtained C60On (n = 2～5) and C70O2. Menon[4] stu- died the optimized structures and electronic proper- ties o…     

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。     

C_(60)环酮衍生物C_(66)H_8O与C_(67)H_(10)O顺反异构体的结构及光谱研究

用AM1，INDO/CI方法研究了C60与2-环己烯-1-酮和2-环庚烯-1-酮[2+2]环加成所得衍生物C_(66)H8O和C67H1O的结构。结果表明，两种衍生物的顺反异构体都只具有C1对称，C66H8O的顺式异构具有较低的能量和较小的偶极矩，C67H10的顺式并构体能量较低，但偶极矩较大，以优化构型为基础，计算加成产物的UV谱，对电子跃迁进行了理论指认，并分析了光谱移动的原因。     

Synthesis, characterization, and theoretical study of stable isomers of C70(CF3)n (n = 2, 4, 6, 8, 10)

Reaction of C70 with ten equivalents of silver(I) trifluoroacetate at 320-340 degrees C followed by fractional sublimation at 420-540 degrees C and HPLC processing led to the isolation of a single abundant isomer of C70(CF3)n for n = 2, 4, 6, and 10, and two abundant isomers of C70(CF3)8. These six compounds were characterized by using matrix-assisted laser desorption ionization (MALDI) mass spectrometry, 2D-COSY and/or 1D 19F NMR spectroscopy, and quantum-chemical calculations at the density functional theory (DFT) level. Some were also characterized by Raman spectroscopy. The addition patterns for the isolated compounds were unambiguously found to be C1-7,24-C70(CF3)2, C1-7,24,44,47-C70(CF3)4, C2-1,4,11,19,31,41-C70(CF3)6, Cs-1,4,11,19,31,41,51,64-C70(CF3)8, C2-1,4,11,19,31,41,51,60-C70(CF3)8, and C1-1,4,10,19,25,41,49,60,66,69-C70(CF3)10 (IUPAC numbering). Except for the last compound, which is identical to the recently reported, crystallographically characterized C70(CF3)10 derivative prepared by a different synthetic route, these compounds have not previously been shown to have the indicated addition patterns. The largest relative yield under an optimized set of reaction conditions was for the Cs isomer of C70(CF3)8 (ca. 30 mol % of the sublimed mixture of products based on HPLC integration). The results demonstrate that thermally stable C70(CF3)n isomers tend to have their CF3 groups arranged on isolated para-C6(CF3)2 hexagons and/or on a ribbon of edge-sharing meta- and/or para-C6(CF3)2 hexagons. For Cs- and C2-C70(CF3)8 and for C2-C70(CF3)6, the ribbons straddle the C70 equatorial belt; for C1-C70(CF3)4, the para-meta-para ribbon includes three polar hexagons; for C1-7,24-C70(CF3)2, the para-C6(CF3)2 hexagon includes one of the carbon atoms on a C70 polar pentagon. The 10.3-16.2 Hz 7JF,F NMR coupling constants for the end-of-ribbon CF3 groups, which are always para to their nearest-neighbor CF3 group, are consistent with through-space Fermi-contact interactions between the fluorine atoms of proximate, rapidly rotating CF3 groups.     

DFT Studies on Thermal Stabilities,Electronic Structures,and ~（13）C Chemical Shifts of C_（24）O_2 Based on Fullerene C_（24）（D_6）

Quantum chemical calculations on some possible equilibrium geometries of C24O2 isomers derived from C24 (D6) and C24O have been performed using density functional theory (DFT) method. The geometric and electronic structures as well as the relative energies and thermal stabilities of various C24O2 isomers at the ground state have been calculated at the B3LYP/6-31G(d) level of theory. And the 1,4,2,5-C24O2 isomer was found to be the most stable geometry where two oxygen atoms were added to the longest carbon-carbon bonds in the same pentagon from a thermodynamic point of view. Based on the optimized neutral geometries, the vertical ionization potential and vertical electron affinity have been obtained. Meanwhile, the vibrational frequencies, IR spectrum, and 13C chemical shifts of various C24O2 isomers have been calculated and analyzed.     

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．     

An efficient approach for theoretical study on the low-energy isomers of large fullerenes C90-C140

An approach that consists of a molecular mechanics method based on the second generation reactive empirical bond order (REBO) potential and the more accurate semiempirical method PM3 (Parametric Method No. 3) was proposed to predict the energetically favored isomers of the fullerenes from C90 to C140 at the semiempirical level. All the 578,701 isolated-pentagon-rule isomers of fullerenes from C90 to C140 were enumerated from topological structures and systematically searched using an energy minimization method to select the best 100 low-energy isomers based on the REBO potential for each fullerene. Then these candidate isomers were further optimized by PM3 and ranked again to determine the top low-energy isomers. This approach was applied to calculate the energetically favored isomers of C90-C140. The results of C90-C120 are in good agreement with the published results by quantum-chemical methods. Furthermore, the top five low-energy isomers of C90-C120, as well as C122-C140 which have scarcely been systematically studied before, are also predicted with the approach. The analysis of the structures showed that the hexagon-neighbor rule is an important factor to the stability of C90-C140. The time cost for the systematical search based on the REBO potential was also discussed. It indicates that the approach proposed is efficient for predicting the energetically favored isomers of large fullerenes at the semiempirical level.     

N-甲基吡咯-2-甲醛激发态结构动力学及其溶剂效应的共振拉曼光谱和密度泛函理论研究

获取了覆盖N-甲基吡咯-2-甲醛(NMPCA)A-带和B-带电子吸收共7个激发波长的共振拉曼光谱,并结合含时密度泛函理论(TD-DFT)方法研究了的A-带和B-带电子激发和Franck-Condon区域结构动力学.TD-B3LYP/6-311++G(d,p)计算表明:A-带和B-带电子吸收的跃迁主体为π→π*.共振拉曼光谱可以指认为,11-13振动模式(A-带激发)或者7-11振动模式(B-带激发)的基频、倍频和组合频,其中C=O伸缩振动(ν7)、环的变形振动+N1-C6伸缩振动(ν17)、环的变形振动(ν21)和C6-N1-C2/C2-C3-C4不对称伸缩振动(ν14)占据了绝大部分.这表明NMPCA的Sπ激发态结构动力学主要沿C=O伸缩振动、环的变形振动和环上N1-C6伸缩振动等反应坐标展开.在同一溶剂的共振拉曼光谱中随激发波长由长变短,ν7与ν14的强度比呈现出由强变弱再变强的现象,这种变化规律被认为与Franck-Condon区域Sn/Sπ态混合或势能面交叉有关.溶剂对Sn/Sπ态混合或势能面交叉具有调控作用.     

几种C70^n离子的Jahn-Teller畸变和单态的电子光谱

用INDO系列方法对C70^n(n=+2, +1, -1, -2, -3, -4)进行系统研究, 表明除C70^n三态具有D5h对称性, 其余均发生Jahn-Teller畸变, 导致明显的对称性降低(C2v), 产生30种键长和21种不等同C原子。以优化构型为基础, 计算C70^4^-单态的电子光谱, 其近红外吸收与实验值一致, 同时预测了C70^2^+单态的光谱。     

Isolation of three isomers of Sm@C84 and X-ray crystallographic characterization of Sm@D(3d)(19)-C84 and Sm@C2(13)-C84

Three isomers with the composition Sm@C(84) were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm(2)O(3). These isomers were labeled Sm@C(84)(I), Sm@C(84)(II), and Sm@C(84)(III) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni(II)(octaethylporphyrin) reveals the identities of two of the isomers: Sm@C(84)(I) is Sm@C(2)(13)-C(84), and Sm@C(84)(III) is Sm@ D(3d)(19)-C(84). Sm@C(84)(II) can be identified as Sm@C(2)(11)-C(84) on the basis of the similarity of its UV/vis/NIR spectrum with that of Yb@C(2)(11)-C(84), whose carbon cage has been characterized by (13)C NMR spectroscopy. Comparison of the three Sm@C(84) isomers identified in this project with two prior reports of the preparation and isolation of isomers of Sm@C(84) indicate that five different Sm@C(84) isomers have been found and that the source of samarium used for the generation of fullerene soot is important in determining which of these isomers form.     

3He NMR as a sensitive probe of fullerene reactivity: [2 + 2] photocycloaddition of 3-methyl-2-cyclohexenone to C70

The [2 + 2] photoadditions of 3-methyl-2-cyclohexenone to C70 and 3He@C70 have been studied by a combination of HPLC chromatography and FAB-MS, as well as IR and 1H and 3He NMR spectroscopies. The total yield of the mixture of monoadducts was 55% (67% on the basis of the recovered C70). The use of 3He NMR was especially powerful in determining the regioselectivity of the photoaddition reaction of enone to C70. Results of the 3He NMR experiments conducted on the product mixture implicate the two [6,6] bonds closest to the poles of the fullerene (C1-C2 and C5-C6) in the photoaddition process. This reaction mode is analogous to that of most thermal addition reactions to C70. Separation and characterization of the product mixture shows that eight distinct monoadducts are formed in the photoaddition, namely, the four diastereomeric adducts to the C1-C2 and C5-C6 bonds of the C70 cage, each consisting of cis- and trans-fused isomers in a ratio of 2:3. The major mode of photoaddition, accounting for 65% of the product mixture, involves addition to the C1-C2 bond of the ovoid fullerene. Mechanistic implications of these findings are discussed.     

C77N+异构体的稳定性和电子光谱研究

All of the possible 21 isomers for C77N+, an isoelectronic molecule of C78, were investigated by the INDO methods based on C78(C2V). It indicates from optimization that the most stable isomer is that the nitrogen atom substitutes C(78) located at the C(78)-C(73) bond passed through by the Y shortest axis and the atoms near the Z longest axis are also easy to substitute, whereas the atoms near the X shortest axis are relatively difficult to substitute. At the same time, C78 was compressed a little and ready to perform the further reaction to form C77 NR at the location of substitution. Electronic spectra of C77N+ were calculated by INDO/SCI method and electronic transition was theoretically assigned. The red shift of absorption peaks for electronic spectra of C77N+ took place compared with that of C78(C2V) because of its narrower LUMO HOMO energy gap. There are great differences in characteristic absorptions among C77N+ isomers, which can be considered as evidence of the formation for each isomer.     

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.     

Preparation and NMR characterization of C70H10: cutting a fullerene pi-system in half

Three isomers of C70H10 were prepared by Zn(Cu) reduction of C70. Three chromatographic bands were identified as C70H10 species by MALDI-FT mass spectrometry, and these compounds were isolated by repeated HPLC treatments. The major isomer (2) was characterized by 1H and 13C NMR, while the minor isomers 3-4 were isolated in such small quantities that only 1H NMR analysis was possible. 1H-coupled and 1H-decoupled 13C NMR of 2 established a 7,8,19,26,33,37,45,49,53,63-substitution pattern. This assignment was confirmed by HMBC and DFQ-COSY experiments. This structure is completely reasonable, as we found that 2 results exclusively from reduction of the 7,19,23,27,33,37,44,53-C70H8 that is formed in the course of the Zn(Cu) reduction of C70.     

Theoretical Studies on Stabilities and Spectroscopy of C78O5

The semi-empirical AM1 and INDO/CIS methods as well as density function theory were used to study equilibrium geometries and spectroscopic properties of the possible isomers of C78O5 based on C2v-C78. The most stable geometry of C78O5 is 28,29,30,31,52,53,70,71,73,78-C78O5(A) with one annulene-like structure and four epoxide structures. Compared with that of C2v-C78, the blue-shift in the electronic absorption spectra of C78O5 isomers is predicted. The reason for the blue-shift effect is discussed and the electronic transitions are assigned. The IR and NMR spectra of C78O5 are explored with the AM1 and B3LYP/6-31G methods based on the B3LYP/6-31G optimized geometries.     

X-ray Crystallographic Characterization of New Soluble Endohedral Fullerenes Utilizing the Popular C(82) Bucky Cage. Isolation and Structural Characterization of Sm@C(3v)(7)-C(82), Sm@C(s)(6)-C(82), and Sm@C(2)(5)-C(82)

Three isomers of Sm@C(82) that are soluble in organic solvents were obtained from the carbon soot produced by vaporization of hollow carbon rods doped with Sm(2)O(3)/graphite powder in an electric arc. These isomers were numbered as Sm@C(82)(I), Sm@C(82)(II), and Sm@C(82)(III) in order of their elution times from HPLC chromatography on a Buckyprep column with toluene as the eluent. The identities of isomers, Sm@C(82)(I) as Sm@C(s)(6)-C(82), Sm@C(82)(II) as Sm@C(3v)(7)-C(82), and Sm@C(82)(III) as Sm@C(2)(5)-C(82), were determined by single-crystal X-ray diffraction on cocrystals formed with Ni(octaethylporphyrin). For endohedral fullerenes like La@C(82), which have three electrons transferred to the cage to produce the M(3+)@(C(82))(3-) electronic distribution, generally only two soluble isomers (e.g., La@C(2v)(9)-C(82) (major) and La@C(s)(6)-C(82) (minor)) are observed. In contrast, with samarium, which generates the M(2+)@(C(82))(2-) electronic distribution, five soluble isomers of Sm@C(82) have been detected, three in this study, the other two in two related prior studies. The structures of the four Sm@C(82) isomers that are currently established are Sm@C(2)(5)-C(82), Sm@C(s)(6)-C(82), Sm@C(3v)(7)-C(82), and Sm@C(2v)(9)-C(82). All of these isomers obey the isolated pentagon rule (IPR) and are sequentially interconvertable through Stone-Wales transformations.