末端基团对芴类衍生物分子非线性光学性质的影响

通过采用预估矫正的时域有限差分方法数值求解速率方程-光场强度方程,研究了纳秒激光脉冲在具有不同末端基团的对称性芴类衍生物分子2,7-双(4′-(二甲基氨基)苯乙烯基)-9-氢-芴(F1分子)和2,7-双(4′-硝基苯乙烯基)-9-氢-芴(F2分子)中的动力学传播过程以及光限幅效应,分析了两种分子的光限幅特性随传播距离(z)、粒子数密度(N)以及脉冲宽度(τ)的变化情况,并且拟合了两种分子的动态双光子吸收(TPA)截面。计算结果表明,该系列分子具有较大的双光子吸收截面以及较好的光限幅效应。此外,F2分子的末端基团―NO_2与F1分子的末端基团―N(CH_3)_2相比具有更强的得电子能力,因而使得F2分子具有更大的跃迁偶极矩,双光子吸收截面增大,光限幅效应更为明显。     

用几个新液晶毛细管色谱柱分离二甲苯、甲酚和二甲酚异构体

近年来已有二百多种液晶气相色谱固定液,用来分离各种异构体.国内研究较多的是芳羧酸酯类液晶,用来分离各种二元取代苯异构体.我们也用此类液晶色谱柱分离了一些芳香族化合物的异构体.为了改进这类液晶固定液的性能,我们曾把极性基团引入这类液晶分子的对苯二酚环上,发现引入一个邻位溴原子,对二元取代苯异构体有较好的分离性能.为了进一步研究这类含溴的芳羧酸酯类液晶,把液晶分子两端的烷氧基碳数增加,并把它们涂在玻璃毛细管柱上,研究它们对二甲苯、甲酚的二元取代异构体的分离性能.     

客体分子末端基团驱动的七元瓜环类轮烷自组装

以1,2-二(4-吡啶基)乙烯为母体,设计合成了系列基于烷基链末端基团分别为—COOH,—CH_2Br和—CH_3的阳离子型线性客体分子(G1~G3).研究结果表明,末端基团为—COOH的客体分子G1可驱动七元瓜环滑过1,2-二(4-吡啶基)乙烯形成[2]类轮烷分子梭及[3]类轮烷;客体分子G2和G3则不能驱动七元瓜环滑过吡啶基乙烯母体部分,但是G2的—CH_2Br基团可驱动七元瓜环靠近吡啶基乙烯基团并形成稳定的[2]类轮烷.这一现象可归因于链状分子末端基团与瓜环端口羰基氧作用时的静电势差异.     

含CS配体的单、双核钌羰基化合物Ru（CS）（CO）n（n=4,3）和Ru2（CS）2（CO）n（n=7,6,5,4）的理论研究

采用2种密度泛函方法MPW1PW91和BP86对中性单核Ru(CS)(CO)n(n=4,3)及双核Ru2(CS)2(CO)n(n=7,6,5,4)化合物进行理论计算研究,优化出25个异构体.研究发现,单核配位饱和Ru(CS)(CO)4的2个异构体14-1,14-2能量接近,其配体呈三角双锥型.对称性为C2v的异构体14-1能量稍低,其CS基团在三角双锥赤道面上.单核配位不饱和Ru(CS)(CO)3的能量最低异构体是由14-1失去1个赤道面上的CO得到的,其对称性为Cs.配位饱和的双核Ru2(CS)2(CO)7能量最低异构体27-1结构中有3个桥配位基团,其中2个是CS基团.配位不饱和的Ru2(CS)2(CO)6存在2个能量接近的异构体,即含3个桥配位基团对称性为Cs的异构体26-1和含2个桥配位基团的异构体26-2.它们的CS基团都是桥配位形式.Ru2(CS)2(CO)5的能量最低异构体25-1含有两个桥配位CS基团,其中一个是4电子供体.而Ru2(CS)2(CO)4的能量最低异构体24-1的两个桥配位CS基团都是4电子供体.在上述各个异构体中,单核Ru(CS)(CO)n(n=4,3)的能量最低异构体的CS基团都位于配体三角双锥及缺顶点结构的赤道面上,双核Ru2(CS)2(CO)n(n=7,6,5,4)能量最低异构体的CS基团都以桥配位形式和Ru原子相连,且在配位不饱和Ru2(CS)2(CO)n(n=5,4)的能量最低异构体中都存在4电子供体CS基团.离解能研究表明,单核配位饱和的Ru(CS)(CO)4具有一定的热力学稳定性.双核的Ru2(CS)2(CO)n(n=7,6,5)失去1个CO或者分裂为单核的Ru(CS)(CO)4或Ru(CS)(CO)3所需能量都较高,但Ru2(CS)2(CO)6和Ru2(CS)2(CO)5有发生歧化反应的趋势,而Ru2(CS)2(CO)7具有一定的热力学稳定性.     

低聚对亚苯基亚乙烯基分子导线电子传输机理研究

合成了12个OPV分子导线(分成乙酰巯基与氨基端基两个系列),采用导电原子力显微镜和扫描隧道显微镜-裂分结的方法对该类分子导线的电学性能进行了表征.通过分析单分子电阻与分子长度、温度以及电场的依赖关系,发现OPV分子导线的电子传输机理在临界长度为2.0 nm处发生了由隧穿传导向跳跃传导的转变.通过对比分子末端分别为巯基和氨基的单分子电导值,考察了不同的连接基团对OPV分子导线电子传输性能的影响,发现末端基团只影响分子的接触电阻,但不改变分子导线本身的电子传输机理.利用密度泛函理论和非平衡格林函数方法对OPV分子导线的电学特性进行了理论研究,结果表明分子的前线轨道能级与金电极的相对位置决定了OPV分子导线的电子传输机理.     

2, 3-二氰基-2, 3-二(p-取代苯基)丁二酸二乙酯的分子结构和 晶体结构

以X射线晶体结构分析方法测定了2,3-二氰基-2,3-二(p-X 取代苯基)丁二酸二乙酯(X=OGH_3,CH_3和 Cl)的两种异构体的晶体结构和分子结构.确定了高熔点者为 dl-异构体,低熔点者为meso-异构体.观察到的重要结构信息是,这些分子内存在着显著的空间阻碍,中心 C—C 键的键长有明显的键长增长效应,而且 meso-异构体的键长增长效应比 dl-异构体更大.     

三态不饱和三核钌羰基化合物的理论研究

采用两种密度泛函方法和两种有效核势基组对中性不饱和三核钌羰基化合物Ru3(CO)n(n=11,10,9)的三态异构体进行理论计算,优化出8个稳定异构体.研究发现,三态异构体中带有多个非端羰基的异构体能量较低.对同一分子的三态异构体,所含非端羰基数目越多,则能量也越低.     

锁核酸分子信标在分子识别与生物分析中的应用

分子信标是一种荧光探针,闭合时呈发夹结构。其5'末端修饰荧光基团,3'末端修饰猝灭基团。当目标存在时,环部与目标结合,发夹打开,发出荧光。锁核酸是一类双环状寡核苷酸衍生物,能够遵循碱基互补配对原则与核酸结合。锁核酸分子信标技术,结合了分子信标无需分离未结合探针而直接检测的优势和锁核酸亲合力强、热稳定性好、抗酶切以及体内无毒等特点,在核酸检测方面具有灵敏度高、特异性好的独特优势,近年来得到广泛关注。本文介绍了锁核酸修饰分子信标的结构、功能、设计要点,及其研究现状和一些重要进展,并讨论了目前锁核酸分子信标在分子识别及生物分析中的应用及存在的问题和发展前景。     

C_(70)PH可能异构体的结构与稳定性的理论研究

分别用半经验的AM1, PM3及MNDO方法研究了富勒烯衍生物C_(70)PH的12种可能异构体的结构和稳定性。计算结果表明: -PH基团加成在4种6-6键上的稳定构型中,非赤道带6-6键加成的三个异构体为闭环结构,赤道带6-6键加成的一个异构体为开环结构;-PH基团加成在4种6-5键上均可产生开环和闭环2种稳定构型。加成在6-5双键的异构体其闭环构型更稳定,加成在6-5单键的异构体其开环构型更稳定。闭环异构体中-PH基团加成在碳球极处6-6键上的构型1,2最稳定,开环异构体中-PH基团加成在赤道带6-6键上的构型8最稳定。     

2, 3-二氰基-2, 3-二(p-取代苯基)丁二酸二乙酯的分子结构和 晶体结构

以X射线晶体结构分析方法测定了2,3-二氰基-2,3-二(p-X取代苯基)丁二酸二乙酯(X=OCH~3,CH~3和Cl)的两种异构体的晶体结构和分子结构。确定了高熔点者为dl-异构体,低熔点者为meso-异构体。观察到的重要结构信息是,这些分子内存在着显著的空间阻碍,中心C-C键的键长有明显的键长增长效应,而且meso-异构体的键长增长效应比dl-异构体更大。     

Photoinduced conformational switch of enantiopure azobenzenes controlled by a sulfoxide

Two series of enantiopure azobenzenes with a p-tolylsulfoxide at the ortho or meta position with respect to the azo group, have been regioselectively synthesized. Both can act as enantiopure molecular switches showing different structural features owing to the presence of the stereogenic sulfur. The photoisomerization process, studied by UV-vis, circular dichroism (CD), NMR, and chiral HPLC evidenced a double role of the sulfoxide. A transfer of chirality from the sulfoxide to the azo system was observed by CD in both cis and trans-isomers of the meta sulfinyl derivatives 3, whereas this perturbation was evident for the ortho sulfinyl series 7 only in the cis isomer. The NMR study evidenced that the s-cis rigid conformation of the bisaromatic sulfoxide was fixing a different orientation of the overall system in each series both in the trans and cis isomers, by forcing a final U-shaped structure in cis-3 and an S-shaped structure in cis-7. Very different values of specific optical rotations were measured in both trans and cis isomers, also reflecting the existence of distinct chiral entities in the photostationary states. The easy and reversible changes occurring between different conformational states could find applications in the photocontrol of several molecular switches.     

Competitive formation of cis and trans derivatives in the nucleophilic substitution reactions of cyclophosphazenes having a mono-spiro P-NHR group

Nucleophilic substitution reactions of N(3)P(3)Cl(4)[NH(CH(2))(3)NMe] (1) and N(3)P(3)Cl(4)[NH(CH(2))(3)O] (2) with mono-functional alcohols (methanol, 2,2,2-trifluoroethanol, phenol) and a secondary amine (pyrrolidine) were used to investigate the relationship between the incoming nucleophile and the proportions of products with substituents that are cis or trans to the spiro NH moiety. The reaction products were characterized by elemental analysis, mass spectrometry, (1)H and (31)P NMR spectroscopy and the configurational isomers by X-ray crystallography. Six products have been characterised with the substituent cis to the spiro NH group for the alcohol (methanol, phenol) and pyrrolidine derivatives of both compounds 1 and 2, compared to just one derivative with the substituent trans to the spiro NH group, that for the pyrrolidine derivative of compound 2. For each reaction the relative proportions of cis and trans isomers were determined by (31)P NMR measurements of the reaction mixtures. It was found that the reactions of compound 1 with all three alcohols and of compound 2 with methanol lead to exclusive formation of isomers with the substituent cis to the NH moiety, whereas all other reactions lead to mixtures of cis and trans isomers in different ratios under standard reaction conditions. However, when crown ether is included in the reaction medium for the reactions of compound 2 with both 2,2,2-trifluoroethanol and phenol, it is found that only cis isomers are formed. All these results are rationalised in terms of the competition between at least two effects; the cis-directing effect by hydrogen bonding of the incoming nucleophile to the spiro N-H group already present on the cyclophophazene ring and the cis-directing effect of the sodium cation coordinating to the oxygen lone pairs of the P-O moiety of the spiro ring.     

Spectroscopic Characterization of the Geminal Isomer of Lewisite

Abstract

Lewisite is generally a mixture of several components with the trans isomer of lewisite being the predominant compound. A geminal isomer has not been previously reported as one of the components of the mixture. In the lewisite samples we examined, the geminal isomer, dichloro(l-chlorovinyl)arsine, comprised 2.7 per cent of the total material compared to 95.2 and less than 1 per cent, respectively, for the trans and cis isomers. The remaining fraction was not identified. The geminal isomer of lewisite has been characterized along with the trans and cis isomers using several spectroscopic techniques. Proton NMR of the geminal isomer produced a coupling constant consistent with vinylic protons in a geminal configuration. Mass spectrometry and infrared spectroscopy characterizations were based on an ethanedithiol derivative of the lewisite isomers with gas chromatography used to first separate the derivatized isomers. The electron ionization massspectra of the trans and cis derivatives were very similar, but significant differences were observed in the mass spectrum of the geminal form. Infrared absorption spectra were obtained for the trans and geminal derivatives with significant differences observed between the two, but the method was not sensitive enough to detect the cis isomer.

     

Mechanistic study of trans⇆cis isomerization of the substituted azobenzene moiety bound on a liquid‐crystalline polymer

A mechanistic study of the trans?cis isomerization of the azobenzene moiety in a side‐chain liquid‐crystal polymer system was carried out with six liquid‐crystalline polymethacrylates in which different electron‐withdrawing substituents were attached to the para‐positions of the azobenzene chromophores. Compared to the non‐nitro‐substituted azo polymers, the nitro‐substituted azo polymers exhibited two quite different behaviors: an extraordinarily high reaction rate of the thermal cis–trans isomerization and an unexpected composition of cis–trans isomers obtained from the photochemical trans–cis isomerization process. A potential energy profile for the isomerization process was established on basis of the structures of the proposed transition states and was employed to elucidate the reaction mechanism. The results confirmed that the nitro‐substituted azo polymer system proceeded via a rotation mechanism in either direction of the trans?cis isomerization reaction, whereas the non‐nitro‐substituted species were more likely to follow an inversion mechanism. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2296–2307, 2001     

2种偶氮席夫碱类化合物的合成及其热致变色性质

摘 要 合成了两种偶氮席夫碱类化合物,通过元素分析,核磁共振氢谱,红外光谱表征了其结构, 经紫外光谱测试表明,这两种化合物具有良好的热致变色性质,在恒定温度下,其trans-cis吸收波长的变化和时间的变化有较好的线性关系。     

Syntheses of shuttlecock- and bowl-equipped phenylazopyridines and photomodulation of their coordination ability to Zn-porphyrin

Shuttlecock- and bowl-equipped 4-(phenylazo)pyridine derivatives, which bear substituents that allow the pyridine moiety to protrude in the trans form but hinder it in the cis form, have been designed and synthesized. These molecules show cis/trans photoisomerization despite the presence of bulky substituents. ¹H NMR titration with Zn-porphyrin showed that the trans isomers coordinate to Zn-porphyrin much stronger than the cis isomers.     

含硅香原料研究(Ⅵ)——顺(反)-1-取代-3-三甲硅基环己醇的合成、~(13)CNMR谱及其香气评定

合成并分离得到 7对 1 取代 3 三甲硅基环己醇的顺、反异构体 ,它们的结构通过 1HNMR、13 CNMR、MS谱及GC(测其纯度 )测定 ,利用 13 CNMR确定了各对顺、反异构体的构型 .评定了各化合物的香气 ,大部分化合物具有甜香或甜香与木香香气 ,其中 (反 ) 1 正丁基 3 三甲硅基环己醇具有甜香和木香香气 ,香气透发 ,留香持久 ,质量上乘     

Stereochemistry of Molecular Figures-of-Eight

A trans isomer of a figure-of-eight (Fo8) compound was prepared from an electron-withdrawing cyclobis(paraquat-p-phenylene) derivative carrying trans-disposed azide functions between its two phenylene rings. Copper(I)-catalyzed azide-alkyne cycloadditions with a bispropargyl derivative of a polyether chain, interrupted in its midriff by an electron-donating 1,5-dioxynaphthalene unit acting as the template to organize the reactants prior to the onset of two click reactions, afforded the Fo8 compound with C(i) symmetry. Exactly the same chemistry is performed on the cis-bisazide of the tetracationic cyclophane to give a Fo8 compound with C(2) symmetry. Both of these Fo8 compounds exist as major and very minor conformational isomers in solution. The major conformation in the trans series, which has been characterized by X-ray crystallography, adopts a geometry which maximizes its C?H???O interactions, while maintaining its π???π stacking and C?H???π interactions. Ab initio calculations at the M06L level support the conformational assignments to the major and minor isomers in the trans series. Dynamic (1) H?NMR spectroscopy, supported by 2D (1) H?NMR experiments, indicates that the major and minor isomers in both the cis and trans series equilibrate in solution on the (1) H?NMR timescale rapidly above and slowly below room temperature.     

含硅香原料研究(VI)－顺(反)-1-取代-3-三甲硅基环己醇的合成、13C NMR谱及其香气评定

合成并分离得到７对１－取代－３－三甲硅基环己醇的顺、反异构体,它们的结构通过＾Ｈ ＮＭＲ、＾１３Ｃ ＮＭＲ、ＭＳ谱及ＧＣ（测其纯度）测定,利用＾１３Ｃ ＮＭＲ确定了各对顺、反异构体的构型。评定了各化合物的香气,大部化合的具有甜香或甜香与木香香气,其中（反）－１－正丁基－３－三甲硅基环己醇具有甜香和木香香气,香气透发,留香持久,质量上乘。     

Fine tuning the structure of the Cu2+ complex with the prion protein chicken repeat by proline isomerization

The interaction between the single hexarepeat unit of chicken prion protein [ChPrP(54-59)] and Cu(II) was investigated by NMR, finding different coordination modes for the trans/trans and cis/trans isomers.