LaH分子的X1∑+态的势能函数

应用原子分子反应静力学原理导出LaH分子的电子状态和可能的离解极限,考虑相对论紧致有效势RCEP(RelativisticCompactEffectivePotential)近似下,用QCISD方法计算了LaH分子基态X1∑+的平衡几何Re和离解能De为2.125A和2.623eV,并在计算出来的一系列单点势能基础上,用正规方程组拟合Murrell-Sorbie(M-S)势能函数,得到相应态的解析势能函数,由此计算对应的光谱参数,其Be、ae、ωe和ωexe的理论值,分别为:3.7333、0.0723、1461.73和21.383cm-1.     

NX(a 1Δ, X=F、Cl、Br)分子结构与ωe～Re关联模型

基于不少双原子分子的稳定激发态系列中存在已知ωe而未给出Re的现象,本文提出了ωe～Reα=C的理论模型,对近60个双原子分子的光谱数据进行了论证,并与量子力学计算结果进行了比较.结果表明,该模型具有通用性与可靠性.结合NX(a 1Δ)替代O2(a 1Δg)的新激光系统可能性研究需要,应用CIS、B3LYP与MCSCF方法,在6-311＋g(3df)基水平计算了NX(X=F、Cl、Br)第一激发态（a 1Δ）的结构,导出了解析势能函数.     

基态Li2O＋分子的结构和势能面研究

以6-311＋＋G(d)为基函数, 采用CASSCF方法优化出Li2O＋分子的稳定构型为线形Li-O-Li (C∞V), 电子组态为2∏, 并对平衡核间距、离解能和基态简正频率进行了计算. 根据原子分子反应静力学原理, 导出了Li2O＋分子的合理的离解极限. 并运用多体展式理论方法首次导出了基态Li2O＋分子的分析势能函数, 绘出了势能等值图, 其势能等值图准确地再现了Li2O＋分子的平衡结构特征.     

PdH2、YH2分子的结构与势能函数

用密度泛函理论的B3LYP方法,对钯和钇原子采用SDD收缩价基函数,氢原子采用6-311＋＋G**全电子基函数,对PdH2和YH2体系的结构进行优化计算,得到PdH2分子最稳态为C2v构型,电子组态为1A1,平衡核间距RPdH=0.1692 nm,键角∠HPdH=29.4°,离解能De=5.5212 eV,基态简正振动频率:ν1(b2)=1470.1 cm－1、ν2(a1)=1007.9 cm－1、ν3(a1)=2907.0 cm－1.YH2分子最稳态也为C2v构型,电子组态2A1,RYH=0.1962 nm,∠HYH=114.3°,De=5.6691 eV,基态简正振动频率:ν1(b2)=1457.9 cm－1、ν2(a1)=476.0 cm－1、ν3(a1)=1506.3 cm－1.由微观过程的可逆性原理分析了分子的可能离解极限.并用多体项展式理论方法分别导出基态PdH2和YH2分子的势能函数,其等值势能面图准确地再现了PdH2和YH2分子的结构特征和离解能,由此讨论了Pd ＋ H2和Y ＋ H2分子反应的势能面静态特征.     

气相中CrO2^＋主活化甲烷C—H键的理论研究

用密度泛函UB3LYP／6-311＋＋G＊＊方法计算研究了气相中CrO2^＋（2^A1/4^A＂）活化甲烷C—H键的微观机理，找到了四条反应通道．对其中涉及的两态反应（TSR）进行了分析，并对影响反应机理和反应速率的势能面交叉现象（potential energy surfaces crossing）进行了详细讨论，进而运用Hammond假设和Yoshizawa等的内禀坐标单点垂直激发计算的方法找出了一系列势能面交叉点[crossing points（CPs）]，并作了相应的讨论．进一步用碎片分子轨道理论[fragment molecular orbital（FMO）]对TS1中的轨道相互作用进行了分析，解释了CrO2^＋活化甲烷C—H键的机理．     

PuC和PuC2的分子结构与势能函数

采用密度泛函B3LYP方法和相对论有效原子实理论模型优化出PuC和PuC2分子稳定构型,其电子状态分别为X5Σ－和X5A2.PuC2分子为C2v构型,其∠CPuC=147.67°,平衡核间距Re=0.22819 nm, 离解能De=5.543 eV, 并计算出谐振动频率:ν1=61.736 cm－1、ν2=229.894 cm－1、ν3=305.582 cm－1.在此基础上,运用多体项展式理论方法,导出了基态PuC2分子的分析势能函数,该势能面准确地再现了PuC2分子的稳定结构,并根据势能面等值图讨论了PuC＋C反应和Pu＋C2反应的势能面静态特征.     

He2+和He2++分子离子基态和激发态的特性研究

采用SAC/SAC-CI方法在CC-PV5Z基组下, 计算研究了He2+、He2++的基态及低激发态的分子特性, 给出了其基态和一些激发态的势能函数和光谱数据(Be、αe、ωe和ωeχe). 从群论出发推导了相应状态的离解极限；与已有实验结果的He2+(X2Σu+)相比, 计算结果令人满意. 还计算了激发态2Πu、4Σu+和4Πg的结构与光谱数据. 对于He2++, 计算的九个电子态中只有三个态(X1Σg+、1Σg+和1Σu+)属束缚态, 并得到了其光谱常数. 用价键理论模型的不相交规则对He2++基态的势能曲线极大点产生的原因做了较好的分析.     

PdYH分子的结构与势能函数

用密度泛函理论的B3LYP方法, 对钯和钇原子采用SDD收缩价基函数, 氢原子采用6-311＋＋G**全电子基函数, 对PdY和PdYH体系的结构进行优化. 计算表明: PdY分子的几何构型为C_∞v, 其基态为X²Σ^＋态, 键长R＝0.24168 nm, 离解能为D_e＝2.8261 eV, 谐振频率ω_e＝254.0656 cm^－1, 并拟合得到Murrell-Sorbie势能函数; PdYH分子最稳态为C_s构型, 电子组态为¹A', 平衡核间距R_PdY＝0.24281 nm, R_YH＝0.19824 nm, 键角∠PdYH＝116.7157°, 离解能D_e＝5.6146 eV, 基态简正振动频率: 对称伸缩振动频率ν₁ (a')＝348.2909 cm^－1, 弯曲振动频率ν₂ (a')＝243.3382 cm^－1, 反对称伸缩振动频率ν₃ (a')＝1442.2695 cm^－1. 由微观过程的可逆性原理分析了分子的可能离解极限. 并用多体项展式理论方法分别导出基态PdY和PdYH分子的势能函数, 其等值势能面图准确地再现了PdY和PdYH分子的结构特征和离解能, 由此讨论了Pd＋Y＋H分子反应的势能面静态特征.     

BF分子X1∑+,A1∏和B1∑+电子态的势能函数

使用SAC/SAC-CI和D95＋＋,6-311＋＋g,6-311＋＋g^＊＊及D95（d）基组,分别对BF分子的基态X^1∑^＋、第一简并激发态A^1∏和第二激发态B^1∑^＋的平衡结构和谐振频率进行优化计算.对所有计算结果进行比较,得出6-311＋＋g^＊＊基组为最优基组.运用6-311＋＋g^＊＊基组和SAC方法对基态X^1∑^＋,SAC-CI方法对激发态A^1∏和B^1∑^＋进行单点能扫描计算,并用正规方程组拟合Murrell-Sorbie函数,得到相应电子态的势能函数解析式,由得到的势能函数计算了与X^1∑^＋,A^1∏和B^1∑^＋态相对应的光谱常数,结果与实验数据较为一致.     

BH分子X1∑+、A1∏和B1∑+态的势能函数

利用SAC/SAC-CI方法,使用D95++、6-311++g及cc-PVTZ等基组,对BH分子的基态(X1∑+)、第一简并激发态(A1∏)及第二激发态(B1∑+)的平衡结构和谐振频率进行了优化计算.通过对三个基组计算结果的比较,得出了cc-PVTZ基组为三个基组中的最优基组的结论;使用cc-PVTZ基组,利用SAC的GSUM(group sum ofoperators)方法对基态(X1∑+),SAC-CI的GSUM方法对激发态(A1∏和B1∑+)进行单点能扫描计算,用正规方程组拟合Murrell-Sorbie函数,得到了相应电子态的完整势能函数;从得到的势能函数计算了与基态(X1∑+)、第一简并的激发态(A1∏)和第二激发态(B1∑+)相对应的光谱常数(Be、αe、ωe和ωeXe),结果与实验数据较为一致.其中基态、第一激发态与实验数据吻合得较好.     

Studies on 1, 2, 4-Benzothiadiazine 1, 1-Dioxide IX.1 Synthesis and Pharmacological Evaluation of 1, 2, 4-Benzothiadiazine 1, 1-Dioxide Biphenyl Tetrazoles as Angiotensin II Antagonists

In the course of our investigations on the development of cardiovascular agents, 3-butyl-2-[2′-(2H-tetrazol-5-yl)bipheny]-4-yl]methyl-2H-1, 2, 4-benzothiadiazine 1, 1-dioxide ( 2 ) was considered as a potential angiotensin II antagonist on the basis of bioisosteric replacement of the quinazoline ring of compound 1 with a 1, 2, 4-benzothiadiazine 1, 1-dioxide ring system. Alkylation of 6 with 4 afforded 7 and 8 in 24% and 28% yields, respectively. An attempt to remove the trityl group of compounds 7 and 8 under acidic condition gave the ring opened products 9 and 11 in 28% and 36% yields, respectively. However, compounds 2 and 10 were obtained in 46% and 85% yields when compounds 7 and 8 were refluxed in methanol. Preliminary assays of compounds 9 and 11 against angiotensin II receptors revealed weak activity with IC₅₀ values of 3.6 μM and 5.4 μM, respectively. Compound 10 (IC₅₀ = 87 nM) exhibited stronger binding affinity than compound 2 (IC₅₀ = 750 nM).     

Reaction of 1, 1-Di-p-methoxyphenyl-2, 2-dinitroethylene and 1, 1-Di-O-methoxyphenyl-2, 2-dinitroethylene with 1-Benzyl-1, 4-dihydronicotinamide： Evidence for Concerted Electron-hydrogen Atom Transfer Mechanism

1,1-Di-p-methoxyphenyl-2, 2-dinitroethylene reacts with 1-benzyl-1, 4-dihydronicotinamide (BNAH) in deaerated acetonitrile to give 1,1-di-p-methoxyphenyl-2, 2-dinitroethane,while 1,1-di-O-methoxyphenyl-2, 2-dinitroethylene fails to react with BNAH under the same conditions, which provides evidence for a concerted electron-hydrogen atom transfer mechanism.     

A novel three-component reaction of 1, 1-dicyano-2-(trifluoromethyl)ethylenes,primary arylamines,and ketones

1, 1-Dicyano-2, 2-bis(trifluoromethyl)ethylene and 3, 3-dicyano-2-(trifluoromethyl)acrylates react with primary arylamines in the presence of ketones to form 1, 1-aryl-1, 4-dihydropyridme derivatives under mild conditions. The mechanism of this three-component reaction includes the formation of Schiffs bases as intermediates. 1, 4-Dihydropyridine derivatives, which are the products of three-component heterocyclization, were also obtained by reaction the corresponding Schiffs bases with 1, 1-dicyano-2-(trifluoromethyl)ethylenes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 552–559, March, 1993.For preliminary communication see Ref. 1.     

EFFECTS OF SOME PHENYLETHYNYLSILICON COMPOUNDS ON HEAT-CURABLE SILICONE RUBBER Ⅲ 1, 1, 3, 3-TETRAMETHYL-1, 3-DIPHENYLETHYNYL-DISILOXANE*

We have shown that some phenylethynylsilicon compounds are good cure crosslinkersof heat-curable silicone rubber(HCSR). In this paper the effects of 1, 1, 3, 3-tetramethyl-1, 3-diphenylethynyldisiloxane (TMDPDS) as a crosslinker on HCSR were studied. Thevulcanizates with fine mechanical properties could be obtained with suitable amounts ofTMDPDS. Sol fractions, and crosslinking density of vulcanizates and vulcanizationretardation effect of TMDPDS on hydrosilation curing silicone rubber were also discussed.     

Viscosity of the systems m-xylene, +1-propanol, +2-propanol, +1-butanol, +t-butanol

Viscosities, η, of the systems, m-xylene, +1-propanol, +2-propanol, +1-butanol and +t-butanol have been measured for the whole range of composition at 303.15, 308.15, 313.15, 318.15 and 323.15?K. The variation of viscosities has been plotted against mole fraction of alkanols. Viscosities have been found to increase slowly up to a considerable concentration of alkanols, followed by a rapid rise of viscosities at higher concentrations. The slow rise of viscosity is attributed to dissociation of alkanols in m-xylene, while the rapid rise of viscosity is ascribed to self-association of alkanols. Excess viscosities, η^E, have been plotted as a function of mole fraction of alkanols. The curves show negative values for the whole range of composition, with minima occurring in alkanol-rich region.?η?and η^E have been fitted to appropriate polynomial equations. The study shows the effect of branching and chain length of alkanols on?η?and η^E.     

Photo-induced Coupling Reaction of 1, 1-Diphenyl-2, 2-dicyanoethylene with 10-Methyl-9, 10-dihydroacridine

In a previous communication1, we reported a novel photo-induced coupling of 9-fluorenylidenemalononitrile 1 with the coenzyme NADH model 10-methyl-9, 10-dihydroacridine (AcrH2) to give 9-dicyanomethyl-9-(10-methyl-9-acridinyl)fluorene and proposed a mechanism involving photo-induced electron transfer-proton transfer and radical coupling. This is a scarce mechanism for the reaction of NADH models2, which usually takes place by a formal hydride transfer pathway3. In view of the novelty of t…     

RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I

Twenty years ago, the landmark AM1 was introduced, and has since had an increasingly wide following among chemists due to its consistently good results and time-tested reliability--being presently available in countless computational quantum chemistry programs. However, semiempirical molecular orbital models still are of limited accuracy and need to be improved if the full potential of new linear scaling techniques, such as MOZYME and LocalSCF, is to be realized. Accordingly, in this article we present RM1 (Recife Model 1): a reparameterization of AM1. As before, the properties used in the parameterization procedure were: heats of formation, dipole moments, ionization potentials and geometric variables (bond lengths and angles). Considering that the vast majority of molecules of importance to life can be assembled by using only six elements: C, H, N, O, P, and S, and that by adding the halogens we can now build most molecules of importance to pharmaceutical research, our training set consisted of 1736 molecules, representative of organic and biochemistry, containing C, H, N, O, P, S, F, Cl, Br, and I atoms. Unlike AM1, and similar to PM3, all RM1 parameters have been optimized. For enthalpies of formation, dipole moments, ionization potentials, and interatomic distances, the average errors in RM1, for the 1736 molecules, are less than those for AM1, PM3, and PM5. Indeed, the average errors in kcal x mol(-1) of the enthalpies of formation for AM1, PM3, and PM5 are 11.15, 7.98, and 6.03, whereas for RM1 this value is 5.77. The errors, in Debye, of the dipole moments for AM1, PM3, PM5, and RM1 are, respectively, 0.37, 0.38, 0.50, and 0.34. Likewise, the respective errors for the ionization potentials, in eV, are 0.60, 0.55, 0.48, and 0.45, and the respective errors, in angstroms, for the interatomic distances are 0.036, 0.029, 0.037, and 0.027. The RM1 average error in bond angles of 6.82 degrees is only slightly higher than the AM1 figure of 5.88 degrees, and both are much smaller than the PM3 and PM5 figures of 6.98 degrees and 9.83 degrees, respectively. Moreover, a known error in PM3 nitrogen charges is corrected in RM1. Therefore, RM1 represents an improvement over AM1 and its similar successor PM3, and is probably very competitive with PM5, which is a somewhat different model, and not fully disclosed. RM1 possesses the same analytical construct and the same number of parameters for each atom as AM1, and, therefore, can be easily implemented in any software that already has AM1, not requiring any change in any line of code, with the sole exception of the values of the parameters themselves.     

1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis,conformational preferences in gas and solution by GED,NMR and theoretical calculations

1-Methylthio-1-phenyl-1-silacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon, was synthesized and its molecular structure and conformational preferences studied by gas-phase electron diffraction (GED) and low temperature ¹³C and ²⁹Si NMR spectroscopy (LT NMR). Quantum-chemical calculations were carried out both for the isolated species and solvate complexes in gas and in polar medium. The predominance of the 1-MeS_axPh_eq conformer in gas phase (1-Ph_eq:1-Ph_ax = 55:45, ΔG° = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1-Ph_eq:1-Ph_ax = 65:35, ΔG° = 0.12 kcal/mol), the experimentally measured ratios being close to that estimated by quantum chemical calculations at both the DFT and MP2 levels of theory.     

STUDIES ON STRUCTURES OF SOME PLATINUM COMPLEXES WITH 1, 1-CYCLOPROPANEDICAR BOXYLATE

The crystal structure, of [Pt(NH_3)_2CPrDCA]. H_2O (Ⅰ), [Pt(CH_3NH_2)_2CPrDCA] (Ⅱ), and [Pt(dmbn) CPrDCA]·2.5H_2O(Ⅲ) (where CPrDCA is 1, 1-cyclopropanedicarboxylate; dmbn is 2, 3-dimethyl-2, 3-butyldiamine) are determined. Compound Ⅰ crystallizes in the orthorhombic space group P_(nma) with the cell dimensions: a=6.517(2), b=9.709(3), c=14.205(5), Z=4, R=0.058. Compound Ⅱ is monoclinic with space group P2_1/n, a=9.648(3), b=8.720(2), c=12.770(4), β=107.12(2), Z=4, R=0.059. Compound Ⅲ belongs to the monoclinic system space group P2_1/m with the cell dimensions: a=6.494(1), b=19.638(3), c=6.606(1), β=94.44(1), Z=2, R=0.038.Electronic structures of the complexes are studied and the correlstion between structure of the amine ligands and biological activity of the complexes is explored.     

Radical Cyclization of 1,n-Enynes and 1,n-Dienes for the Synthesis of 2-Pyrrolidone

2-Pyrrolidones have aroused enormous interest as a useful structural moiety in drug discovery; however, not only does their syntheses suffer from low selectivity and yield, but also it requires high catalyst loadings. The radical cyclization of 1,n-enynes and 1,n-dienes has demonstrated to be an attractive method for the synthesis of 2-pyrrolidones due to its mild reaction conditions, fewer steps, higher atom economy, excellent functional group compatibility, and high regioselectivity. Furthermore, radical receptors with unsaturated bonds (i. e. 1,n-enynes and 1,n-dienes) play a crucial role in realizing radical cyclization because of the ability to selectively introduce one or more radical sources. In this review, we discuss representative examples of methods involving the radical cyclization of 1,n-enynes and 1,n-dienes published in the last five years and discuss each prominent reaction design and mechanism, providing favorable tools for the synthesis of valuable 2-pyrrolidone for a variety of applications.