亚烷基卡宾与亚烷基锂氟类卡宾化学键结构的量子拓扑研究

用ab initio(3-21G)方法对亚烷基卡宾H_2C—C的单线态及三线态结构进行了电子密度拓扑分析,说明了它们的亲电、亲核反应方向,讨论了亚烷基锂氟类卡宾H_2C—CLiF的4种构型,论证了该分子中不存在四元环结构、Li—C键以静电作用为主的特性,并预测了加成反应机理。     

6,6-二烷基富烯与有机锂的反应-双(取代环戊二烯基)钛, 锆衍生物的合成

本文研究了6,6-二烷基富烯与有机锂反应的立体效应。6,6二甲基、甲基乙基、二乙基、甲基苯基富烯与乙基锂易发生环外双键的还原反应。6-甲基-6-正丙基、异丁基富烯同正丁基锂则发生环外双键的加成反应。6,6-多亚甲基富烯[C5H4=C(CH2)n]与有机锂的反应随n值不同而异, n=4的富烯同正丙基锂和正丁基锂进行α-攫氢和环外双键还原的竞争反应; n=5,6 的富烯与乙基锂, 异丙基锂和异丁基锂发生还原反应, 与正丙基俚和正丁基锂则进行加成与还原的竞争反应,n=4 的富烯与芳基锂发生α-攫氢反应, 随n值增大则倾向于加成反应。通过上述反应所得的锂化合物合成了一系列新的仲、叔烷基和烯基取代的环戊二烯基钛、锆衍生物。应用^1HNMR证明了化合物的结构。     

6,6-二烷基富烯与有机锂的反应-双(取代环戊二烯基)钛, 锆衍生物的合成

本文研究了6,6-二烷基富烯与有机锂反应的立体效应。6,6-二甲基、甲基乙基、二乙基、甲基苯基富烯与乙基锂易发生环外双键的还原反应。6-甲基-6-正丙基、异丁基富烯同正丁基锂则发生环外双键的加成反应。6,6-多亚甲基富烯[C_5H-4=C(CH_2)_n]与有机锂的反应随n值不同而异,n=4的富烯同正丙基锂和正丁基锂进行α-攫氢和环外双键还原的竞争反应;n=5,6的富烯与乙基锂、异丙基锂和异丁基锂发生还原反应,与正丙基锂和正丁基锂则进行加成与还原的竞争反应。n=4的富烯与芳基锂发生α-攫氢反应,随n值增大则倾向于加成反应。通过上述反应所得的锂化合物合成了一系列新的仲、叔烷基和烯基取代的环戊二烯基钛、锆衍生物。应用~1H NMR证明了化合物的结构。     

烷烃中碳氢键离解能的估算及其应用

将烷烃中的C－H键看成氢原子H与烷基Ri相连接而成的Ri－H键，以烷基的 HOMO能级和氢原子的轨道能来关联Ri－H键的离解能BDE。研究表明，烷烃分子中 Ri－H键的离能BDE与烷基Ri的极化效应指数PEI（Ri）有良好的线性关系：BDE＝ c+dPEI(Ri)。所得方程具有良好的估算精度。烷基Ri极化效应指数PEI（Ri）在羟 基自由基与烷烃反应速度常数的定量相关中，也得到良好的应用。     

有机硼酸盐的化学IV, 三烷基噻吩基硼酸锂与CO~2的反应

本文研究了三烷基噻吩基硼酸锂与CO~2的反应,发现三烷基噻吩基硼酸锂可与CO~2在高压下进行反应得5-烷基噻吩-2-羧酸;从而证实了三烷基噻吩基硼酸锂与亲电试剂反应时亲电试剂进攻的是噻吩基的5-位,而不是3-位,这一新反应可用于制备噻吩羧酸类化合物。此外,2-烷基噻吩-5-羧酸可以被Raney Ni还原而开环脱硫成一长链羧酸,因而提供了一个将烷基延长5个碳链的新方法。     

取代环戊二烯负离子的三甲基硅基化

以６,６－二烷基富烯与甲基锂、苯基锂或对甲苯基锂所犁 取代环戊二烯基锂与三甲基氯硅烷反应,合成了１１个新的三甲基硅基环戊二烯化合物,其结构经元素分析、ＩＲ和＾１ＨＮＭＲ确证。     

镍催化构筑C(sp3)—C(sp3)键反应研究进展

过渡金属催化的偶联反应是构筑C-C键的高效方法,在有机合成中得到了广泛的应用.然而,相对于Heck反应、Negishi偶联与Suzuki偶联等构筑C（sp²）-C（sp²）键的反应,过渡金属催化的构筑C（sp³）-C（sp³）键的偶联反应较难进行,发展较晚.近年来,烷基-烷基C-C键偶联反应受到广泛的重视,一些高效催化剂被开发出来,其中镍催化剂展示出独特的催化活性和选择性.本文将综述镍催化烷基-烷基C-C键偶联反应最新研究进展,主要包括烷基亲电试剂与金属有机试剂交叉偶联反应、导向基参与的C（sp³）-H键活化的偶联反应、镍-光反应催化剂协同催化偶联反应、烷基亲电试剂与亲电试剂的还原偶联反应和镍催化烯烃加成反应等.     

长链烷基锂与6,6-二烷基富烯的反应研究——取代茂钛、锆化合物的合成

研究了正庚基锂、正辛基锂同 6,6-二烷基富烯反应的立体和溶剂效应对反应类型的影响。在弱极性溶剂中 (方法 A,B) ,正庚基锂、正辛基锂同 6,6-二烷基富烯主要发生加成反应 ;在极性溶剂中 (方法 C) ,则倾向于加成和还原两种反应。利用上述反应形成的环戊二烯基阴离子同Ti Cl4、Zr Cl4反应 ,合成了一系列新的取代茂钛、锆化合物。     

有机硼酸盐的化学 Ⅳ.三烷基噻吩基硼酸锂与CO_2的反应

本文研究了三烷基噻吩基硼酸锂与CO_2的反应.发现三烷基噻吩基硼酸锂可与CO_2在高压下进行反应得5-烷基噻吩-2-羧酸,从而证实了三烷基噻吩基硼酸锂与亲电试剂反应时亲电试剂进攻的是噻吩基的5-位,而不是3-位.这一新反应可用于制备噻吩羧酸类化合物.此外,2-烷基噻吩-5-羧酸可以被Raney Ni还原而开环脱硫成一长链羧酸,因而提供了一个将烷基延长5个碳链的新方法.     

氟代乙烯阳离子的理论研究

用B3LYP和MP2方法及6-31G(d, p)、6-31＋G(d, p)、6-311G(d, p)和6-311＋G(d, p) 基组，对六种氟代乙烯阳离子做了理论研究，优化了它们的基电子态的结构，计算了对应分子的垂直电离势（VIP）和绝热电离势(AIP).结果表明，与具有非平面结构的乙烯阳离子不同，六种氟代乙烯阳离子都只具有平面结构；与分子结构相比，离子结构的C－C键增长， C－F键缩短， CCF键角变小. 自然布居分析计算表明，这些离子的正电荷主要分布在与F原子相连的C原子和各H原子上. B3LYP/6-311＋G(d, p) 级别上计算的各分子的VIP和AIP值和实验值符合得很好. 使用含弥散基函数的基集可以明显提高这类分子的电离势的计算精度.     

Computational treatment of the microsolvation of neutral and zwitterionic forms of alanine

B3LYP/6-31++G** and MP2/6-31++G**//B3LYP/6-31++G** calculations are reported for the structures of neutral alanine–(H₂O)_n and zwitterionic alanine–(H₂O)_n clusters where n = 2–10. Optimized geometries and energies were obtained. In general, with an increasing number of water molecules, the hydrated zwitterionic form becomes more thermodynamically stable. In the presence of six or seven water molecules, the energetics indicate that the two forms may coexist. Eight water molecules are sufficient to computationally guarantee the reported experimental observation of zwitterionic dominance in solution.     

Evaluation of the enthalpy of formation, proton affinity, and gas-phase basicity of gamma-butyrolactone and 2-pyrrolidinone by isodesmic reactions

The knowledge of thermochemical parameters such as the enthalpy of formation, gas-phase basicity, and proton affinity may be the key to understanding molecular reactivity. The obtention of these thermochemical parameters by theoretical chemical models may be advantageous when experimental measurements are difficult to accomplish. The development of ab initio composite models represents a major advance in the obtention of these thermochemical parameters, but these methods do not always lead to accurate values. Aiming at achieving a comparison between the ab initio models and the hybrid models based on the density functional theory (DFT), we have studied gamma-butyrolactone and 2-pyrrolidinone with a goal of obtaining high-quality thermochemical parameters using the composite chemical models G2, G2MP2, MP2, G3, CBS-Q, CBS-4, and CBS-QB3; the DFT methods B3LYP, B3P86, PW91PW91, mPW1PW, and B98; and the basis sets 6-31G(d), 6-31+G(d), 6-31G(d,p), 6-31+G(d,p), 6-31++G(d,p), 6-311G(d), 6-311+G(d), 6-311G(d,p), 6-311+G(d,p), 6-311++G(d,p), aug-cc-pVDZ, and aug-cc-pVTZ. Values obtained for the enthalpies of formation, proton affinity, and gas-phase basicity of the two target molecules were compared to the experimental data reported in the literature. The best results were achieved with the use of DFT models, and the B3LYP method led to the most accurate data.     

Quantum-Chemical Analysis of Coordination of Dimethylsulfoxide Molecules to Sodium and Potassium Cations

Coordination of dimethylsulfoxide molecules to the sodium and potassium cations was investigated by HF/6-31G(d)//HF/6-31G(d) and DFT(B3LYP/6-31G(d)) quantum-chemical methods. The coordination numbers of Na⁺ and K⁺ are found to be five and six, respectively. Thermal effects of complexation were calculated for each stage of the process; these were found to be 197.8, 160.1, 106.9, 88.0, 53.9 [HF/6-31G(d)] and 195.0, 158.5, 108.9, 95.7, 60.0 kJ/mole [B3LYP/6-31G(d)] for Na⁺ (one to five DMSO molecules, respectively); 146.6, 118.7, 90.2, 68.9, 70.0, 49.0 [HF/6-31G(d)] and 144.0, 117.4, 91.7, 78.9, 78.6, 56.4 kJ/mole [B3LYP/6-31G(d)] for K⁺ (one to six DMSO molecules, respectively). Structural parameters and charge distributions are given for the complexes. It is shown that solvation of sodium and potassium cations by DMSO molecules is preferable to solvation by water molecules.     

The 3-21G(N*) basis set: An economical polarized basis set for ab initio studies on nitrogen-containing molecules

The 3-21G basis set shares with its older cousin, the 4-31G basis set, a tendency to overestimate valence angles at nitrogen atoms and to underestimate seriously barriers to inversion at such atoms. The 6-31G* basis set generally yields greatly improved results in these respects. It is here shown that, for a variety of molecules, supplementation of the 3-21G basis set at three- or two-coordinate nitrogen atoms with a set of six d-functions having exponent 1.0 leads to optimized geometries and inversion barriers at such nitrogen centers in good agreement with results obtained with the 6-31G* basis set. This supplemented basis set, designated as 3-21G(N*), also leads to calculated vibrational frequencies in good agreement with those calculated with the 6-31G* basis set. The 3-21G(N*) basis set offers an economical alternative to the 6-31G* basis set, particularly for molecules containing several first-row atoms other than nitrogen.     

β-HMX晶体结构及其性质的高水平计算研究

对β-HMX晶体进行DFT-B3LYP/6-31G计算研究，求得其能带结构和电子结构，探讨了结构-性能关系。从带隙约为5.7eV推知HMX晶体为绝缘体，计算所得晶格间相互作用能为149.29kJ.mol^-^1；计算的升华热(154.08kJ.mol^-^1)与实验值相符。晶体中相邻分子的硝基氧之间点电荷静电势要高，表明该处晶格易于断裂、并可能成为冲击引爆中心。从原子间距和原子间重叠布居分析，发现β-HMX分子之间存在微弱的氢键；环外以硝胺键较强，环内以N-C键较弱，预示该二部位易于引发分解和起爆。     

Li+粘贴CHnCl3-nO2和CFnCl3-nO2( n = 1~3 )自由基：Li+–CHnCl3-nO2和 Li+–CFnCl3-nO2的结构与性质的研究

The structures and stabilities of these still experimentally unknown CH_nCl_(3-n)O_(2-)Li~ and CF_nCl_(3-n)O_(2-)Li~ ionshave been theoretically investigated by ab initio molecular orbital theory and density functional theory(DFT)inconjunction with the 6-311G(d,p),6-311 G(d,p),6-311 G(2d,p)and 6-311 G(2df,2p)basis sets.The optimizedgeometries,chemical bonding and NBO analysis indicate that these complexes of CH_nCl_(3-n)O_(2-)Li~ and CF_nCl_(3-n)O_(2-)Li~ exist as ion-dipole molecules.The calculated affinity energies of these species exceed 41.9 kJ/mol,which arelarge enough to suggest the possibility that these title complexes could be detected as stable species in gas phase byLi~ ion attachment mass spectrometry.     

Self-assembly of asymmetric fan-shaped dendrimers with different generation numbers at the air-water interface

Monolayer formation of two dendrimers containing a hydrophilic core group (COOH) and hydrophobic peripheral groups (anthracene and aryl ether tail groups), 4-{10-[4-(3,5-bis-benzyloxy)-phenyl]-anthracen-9-yl}-benzoic acid (G1) and 4-(10-{4-[3,5-bis-(3,5-bis-benzyloxy)-benzyloxy]-phenyl}-anthracen-9-yl)-benzoic acid (G2), were studied. To understand the mechanism of the self-assembly of these molecules, we measured the surface pressure-surface area (Pi- A) isotherm and investigated the surface texture of Langmuir-Blodgett monolayers transferred onto hydrophilic silicon wafers. Both dendrimers form circular domains at the onset point of surface pressure as a result of the difference in hydrophobicity between the core group and the peripheral end group. The core group has a functional group at the end of dendrimer and can be anchored on the water surface. Upon further compression, monolayer of G1 shows a domain of molecules whereas a monolayer of G2 is aligned in the direction of compression at 10 mN/m. At higher surface pressure (20 mN/m), G1 molecules have several aggregates of domains, but G2 molecules maintain their ordering. These results were confirmed by the electron density profile of G1 and G2 monolayers transferred to silicon substrates, as measured by X-ray reflectivity.     

An ab initio theoretical study of electronic structure and properties of 2'-deoxyguanosine in gas phase and aqueous media

Molecular geometries of two structural forms of 2'-deoxyguanosine (keto-N9R and keto-N7R, R = the sugar moiety) considering both the C2'-endo and C3'-endo conformations of the sugar ring and those of the complexes of these species with two water molecules each were optimized employing the ab initio RHF procedure. A mixed basis set consisting of the 6-311+G* basis set for the nitrogen atom of the amino group and the 4-31G basis set for all the other atoms was used. The RHF calculations were followed by correlation correction of the total energy at the MP2 level. Both the structural forms of 2'-deoxyguanosine were solvated using the polarized continuum model (PCM) of the self-consistent reaction field (SCRF) theory and the corresponding RHF optimized geometries at the RHF and MP2 levels. Geometry optimization was also performed in aqueous media using the Onsager model at the RHF level using the above-mentioned mixed basis set, and subsequently, using the reoptimized geometries, single-point MP2 calculations were performed. It is found that both the keto-N9R and keto-N7R forms of 2'-deoxyguanosine as well as their complexes with two water molecules each would occur, particularly at the water-air interface. Though the normal Watson-Crick-type base pairing would not be possible with the keto-N7R form of 2'-deoxyguanosine(G*), two other (G*-C and G*-T) base pairing schemes may occur with this form of the nucleoside, which may cause mutation. The present calculated geometry of the keto-N9R form of the anti-conformation of 2'-deoxyguanosine including the dihedral angle chi(CN) agree satisfactorily with the available crystallographic results. The present results also agree satisfactorily with those obtained by other authors earlier for the keto-N9R form of 2'-deoxyguanosine using B3LYP and MP2 methods employing the 6-31G* basis set. Using transition state calculations, it is shown that tautomerism of guanine and other similar molecules where the tautomers would coexist would be facilitated by the occurrence of the H(+) and OH(-) fragments of water molecules. Further, this coexistence of the two tautomers appears to make the C8 carbon atom located between the N7 and N9 nitrogen atoms susceptible to attack by the OH(-) group. Thus, an explanation is obtained for the efficient formation of the reaction product 8-hydroxy-2'-deoxyguanosine, which serves as a biomarker for oxidative damage to DNA in biological systems.     

Electronic structure and stability of fullerene C82 isolated-pentagon-rule isomers

All nine isolated-pentagon-rule isomers of fullerene C(82) were investigated by the DFT method with the B3LYP functional at the 6-31G, 6-31G*, and 6-31+G* levels. The distribution of single, double, and delocalized π-bonds in the molecules of these isomers is shown for the first time. The obtained results are fully supported by DFT quantum-chemical calculations of electronic and geometrical structures of these isomers. The molecules of isomers 7 (C(3v)), 8 (C(3v)), and 9 (C(2v)) contain some radical substructures (such as the phenalenyl-radical substructure), which indicates that they are unstable and cannot be obtained as empty molecules. Thus, there is a possibility of obtaining them only as endohedral metallofullerenes or exohedral derivatives. Isomers 1 (C(2)), 2 (C(s)), 4 (C(s)), 5 (C(2)), and 6 (C(s)) with closed electronic shell are supposed to be stable, resembling isomer 3 (C(2)), which has just been extracted experimentally as an empty fullerene. We assume they can be produced as empty molecules.     

A density functional theory study of the structure and vibrational spectra of beta-carotene, capsanthin, and capsorubin

A theoretical study of the structure and the vibrational spectra of the beta-carotene molecule and its derivatives capsanthin and capsorubin is carried out. We first investigate systematically the theoretical method which provides the best results for beta-carotene by performing ab initio calculations at the HF/6-31G(d), SVWN/6-31G(d), PBE0/6-31G(d), BLYP/6-31G(d), B3LYP/6-31G(d), B3LYP/6-31G(d,p), B3LYP/6-311G(d), and B3LYP/6-311G(d,p) levels and by using previous theoretical results available in the literature obtained at the AM1 and BPW91/6-31G(d) levels. The influence of both the level of calculation and the size of the basis set used in the geometry optimization and in the determination of the IR and Raman spectra of this molecule is thus analyzed. It is confirmed that the hybrid functional B3LYP with the basis 6-31G(d) is the method that gives the best results as a whole. By use of this level of calculation, we next optimize the molecular geometries of related molecules of capsanthin and capsorubin, which to the best of our knowledge have only been studied at the semiempirical AM1 level. In addition we calculate the IR and Raman spectra of these molecules at the B3LYP/6-31G(d) level of theory. The results obtained for capsanthin show on the one hand that the double bond of the beta-ionone ring is outside the polyene chain plane, due to the repulsion between the hydrogen atoms of the ring methyl groups and the hydrogen atoms of the polyene chain, and on the other hand that the carbonyl double bond in the other headgroup is very close to planarity with the polyene chain, since in this case such a repulsion does not exist. For the molecule of capsorubin the two carbonyl groups also take the same coplanar orientation relative to the polyene chain. The IR and Raman spectra theoretically computed for these two molecules are finally compared with their experimental spectra and the vibrational normal modes of the main signals are interpreted.