取代环己硅烷类(苯基乙烷和联苯基乙烷系列)液晶化合物分子的基本性质的量子化学研究

取代环己硅烷类液晶化合物是以专利形式报道的一类新型液晶材料.它们具有能降低液晶的粘度和双折射率,使液晶显示器件的响应速度增快,视角变宽等优良性能,可满足在低温下正常工作的要求,具有良好的应用前景[1].关于该类化合物的分子结构和基本性质的实验和理论研究的报道并不多见.因此,开发优良的分子轨道计算方法研究液晶化合物的结构和性质的关系已成为理论化学家们关注的课题,其中,AM1[2]法和PM3[3]法是目前被较多地用于这类研究的半经验分子轨道近似计算方法.     

环己硅烷类液晶化合物的量子化学研究

运用AM1和PM3两种SCF-MO方法，通过能量梯度全优化计算，给出20种环己硅烷类（苯基乙烷系）液晶化合物的稳定几何构型、电子结构和基本性质．联系有机电子结构理论进行了细致的讨论．     

环己硅烷类液晶化合物的量子化学研究: 联苯基乙烷类系列

运用AM1和PM3两种SCF-MO方法, 通过能量梯度全优化计算, 给出了25种环己硅烷类液晶化合物的稳定几何构型、电子结构和生成热、偶极矩等基本性质。联系有机电子结构理论进行了讨论。     

(4R-cis)-6-[2-[2-(4-氟苯基)-5-(1-异丙基)-3-苯基-4-[苯胺(羰基)]-1 H-吡咯-1-基]乙基]-2,2-二甲基-1,3-二氧己环-4-乙酸叔丁酯的波谱学研究

对(4R-cis)-6-[2-[2-(4-氟苯基)-5-(1-异丙基)-3-苯基-4-[苯胺(羰基)]-^1H-吡咯-1-基]乙基]-2,2-二甲基-1,3-二氧己环-4-乙酸叔丁酯的傅里叶变换离子回旋共振质谱(FT-ICR-MS)、核磁共振氢谱(^1H-NMR)、碳谱(^13C-NMR)以及^1H同核位移相关谱(^1H-^1HCOSY)、检出^1H的异核多量子相干谱(HMQC)和^1H检测的异核多键相关谱(HMBC)报道并进行解析。确定了^1H谱、^13C谱中各谱峰的归属,研究了其六元环部分的立体构象,并就空间效应对其化学位移的影响做了初步的探讨。     

Theoretical Studies on Property and Structure of Silacyclohexane-based Liquid Crystal Compounds

11NTRoDUCTIONSilacyclohexane-basedcompoundisanewkindofliquidcrystalcompoundswhichcontainsasiliconatominthemoleculesoastoimprovethecharacteristicsforuseasaliquidcrystalsubstancet13.Todate,fewexperimentalstudiesandtheoreticalresearcheshavebeenperformedonthesecompounds.Inouropinion,thetheQreticalpredictionofmolecularstructuresisprobablyoneofthemostimportantsubjectsforunderstandingtheirproperties.Thispaperdealswiththemoleculargeometries,elec-.ltronicstructures,heatsofformationanddipolemomentso…     

A comparative study by AM1, PM3 and ab initio HF/3-21G methods on the structure and reactivity of monosubstituted carbanion 1,2,4-triazolium ylides

A full conformational analysis of six 1,2,4-monosubstituted carbanion 1,2,4-triazolium ylides 4 a–f was performed using AM1, PM3 and HF/3-21G methods. The C-type conformers were found as the most stable structures by these different methods. This study also includes a qualitative estimation of the chemical behavior of triazolium ylides 4 a–f as nucleophilic agents on the level of ylide carbon atoms. The ab initio 3-21G method seems to be the most suitable in the characterization of these molecular systems.     

侧链聚硅氧烷液晶高分子的合成与表征及应用研究

液晶高分子既具有独特的液晶性 ,又具有高分子的良好材料性能 ,引起了人们的广泛注意[1～ 9] .侧链液晶高分子大多可以作为功能材料 ,对它们的研究有很大的理论与现实意义 .以往报道的此类化合物的介晶基元大多是通过烷氧基与间隔基相连[10 ] .我们以催化活性很高的铂络和物为催化剂 ,通过硅氢加成反应制备了间隔基与介晶基元通过酰氧基相连的两种侧链聚硅氧烷液晶高分子 ,并对它们的性质进行了初步表征 .发现它们具有很好的液晶性 .已有研究表明侧链聚硅氧烷液晶在气相色谱分离结构近似的物质方面 ,具有易涂渍、选择性及热稳定性优于低分子…     

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.     

一系列含T-型二维液晶基元的液晶高分子配体的合成

以４,４′ （α,ω 亚烷基二酰氧）二苯甲酰氯和２,４ 二羟基 ４′ 烷氧基偶氮苯为单体,通过溶液聚合,合成了一系列新的含Ｔ 型二维液晶基元的液晶高分子配体．单体的结构通过元素分析、ＩＲ、１Ｈ ＮＭＲ和ＭＳ等方法确证．高分子配体通过ＧＰＣ、ＤＳＣ、ＴＧ、ＷＡＸＤ和偏光显微镜等方法测试表征,发现所有的高分子配体加热至各自的熔点以上都能形成液晶态,在液晶态可以观察到向列型的丝状织构和纹影织构．它们的熔点（Ｔｍ）和液晶态的清亮点（Ｔｉ）随分子中末端烷氧基增大和柔性间隔段长度增加呈规律性变化．特别值得一提的是,发现末端不含取代基的高分子配体也能产生液晶态,这对该类高分子液晶态生成的机制与液晶态的织构提供了一个新的研究课题［１］．     

Synthesis, Crystal Structure and Conformational Analysis of(E)-5-Methoxy-2-((4-methoxyphenylimino)methyl)phenol

The title compound,(E)-5-methoxy-2-((4-methoxyphenylimino)methyl)phenol(C15H15NO3),crystallizes in monoclinic,space group P21/c with a=9.4361(6),b=10.6212(5),c=12.9338(9),β=93.064(5)o,V=1294.41(14)3,Z=4,Dc=1.320 g/cm3,F(000)=544,Rint=0.116,T=296 K,μ=0.09 mm-1,the final R=0.051 and wR=0.148 for 1836 observed reflections with I2σ(I).An extensive two-dimensional network of C-H…O hydrogen bonds and π-ring interactions are responsible for the crystal stabilization.Intermolecular hydrogen bonds and C-H…π interactions produce R22(14),R44(30) and R44(31) rings.In addition to the molecular geometry from X-ray experiment,the molecular geometry of the title compound in the ground state has been calculated using the semi-empirical(AM1 and PM3) and density functional theory method(DFT)(B3LYP) with 6-31G(d) basis set.To determine the conformational flexibility,molecular energy profile of the title compound was obtained by semi-empirical(PM3 and AM1) and DFT/B3LYP calculations with respect to the selected degree of torsional freedom,which varied from -180° to +180° in a step of 10°.     

Extension of the PDDG/PM3 and PDDG/MNDO semiempirical molecular orbital methods to the halogens

The new semiempirical methods, PDDG/PM3 and PDDG/MNDO, have been parameterized for halogens. For comparison, the original MNDO and PM3 were also reoptimized for the halogens using the same training set; these modified methods are referred to as MNDO' and PM3'. For 442 halogen-containing molecules, the smallest mean absolute error (MAE) in heats of formation is obtained with PDDG/PM3 (5.6 kcal/mol), followed by PM3' (6.1 kcal/mol), PDDG/MNDO (6.6 kcal/mol), PM3 (8.1 kcal/mol), MNDO' (8.5 kcal/mol), AM1 (11.1 kcal/mol), and MNDO (14.0 kcal/mol). For normal-valent halogen-containing molecules, the PDDG methods also provide improved heats of formation over MNDO/d. Hypervalent compounds were not included in the training set and improvements over the standard NDDO methods with sp basis sets were not obtained. For small haloalkanes, the PDDG methods yield more accurate heats of formation than are obtained from density functional theory (DFT) with the B3LYP and B3PW91 functionals using large basis sets. PDDG/PM3 and PM3' also give improved binding energies over the standard NDDO methods for complexes involving halide anions, and they are competitive with B3LYP/6-311++G(d,p) results including thermal corrections. Among the semiempirical methods studied, PDDG/PM3 also generates the best agreement with high-level ab initio G2 and CCSD(T) intrinsic activation energies for S(N)2 reactions involving methyl halides and halide anions. Finally, the MAEs in ionization potentials, dipole moments, and molecular geometries show that the parameter sets for the PDDG and reoptimized NDDO methods reduce the MAEs in heats of formation without compromising the other important QM observables.     

Quantum chemical studies on the structures, properties and decomposition of the azido derivatives of trinitrobenzenes

The geometries,heats of formation and electronic structures of 15 azido-derivatives of 1,2,3-TNB (Ⅰ),1,2,4-TNB (Ⅱ) and 1,3,5-TNB (Ⅲ) have been studied using quantum chemical AMI method at HF level.The effect of azido substitution on the structures and properties of TNBs has been discussed and the relative stability of the title compounds has been established.The processes of the decomposition of the title compounds by breaking C-NO2,C-N3 and CN-N2 bonds are investigated at UHF-AM1 level.It is shown that the decomposition of the title compounds may be initiated by the cleavage of both C-NO2 and N-N2 bonds.     

Quantum Chemical Study on the Thermolysis of Dicyanofuroxan

Recently,thegeometricandelectronicstrUctUreofdicyanofuroxan(3,4-dicyano-l,2,5-oxadiazole-2-oxide)wasstUdiedbyT.Pasinszkiandco-workers,usingabinitiocalcula-honattheHF/6-3lGlevelandx-raycyrstallograPhy.'Beforetheabovework,exPerdrientalstUdyhadsuggestedthatdicyanofuroxancanundergothermolyticcycloreversiontotWomolesofthenovelpenta-atondcmolecule,NCCNO,'whichisofpotentialastrophysicalinterest.Here,theresultSoftheorehcalstUdiesbyAMl'andPM3'methods,usingtheunrestrictedHartree-Fock(UHF)calc…