静电纺丝法制备NiO纳米纤维及其表征

纳米级NiO因具有优良的催化和热敏等性能而被广泛用于催化剂^[1]、电池电极^[2,3]、光电转化材料^[4～6]、电化学电容器^[7～8]等诸多方面.迄今,已成功地制备出N iO的纳米颗粒^[9]、纳米线^[10]及纳米薄膜^[11],但是对于具有准一维结构的NiO纳米纤维的制备及性能研究尚未见报道.     

四(4-重氮基苯基)卟啉的合成及其与聚苯乙烯磺酸钠自组装的研究

卟啉是一类重要的功能性小分子染料,近年来,在光化学治疗^[1,2]、光电转换^[3,4]、传感元件^[5]、烯烃环氧化催化剂^[6]和光敏化剂^[7]等方面的研究与应用引起了人们的广泛注意.通过两亲卟啉分子衍生物,或带有负电荷的卟啉衍生物,特别是带磺酸基的卟啉分子与正离子聚电解质自组装,制备带有卟啉结构单元的LB膜和自组装膜已有很多报道^[8～14].     

4-甲酰基4-苯乙烯基吡啶分子聚集行为的光谱研究

苯乙烯基吡啶化合物,由于它可能在医学方面^[1]和光电子功能材料^[2]方面有实际应用前景,已引起人们的兴趣。苯乙烯吡啶化合物的光化学性质类似于二苯乙烯化合物,在光照下可以发生顺-反异构反应^[3]、加成反应和二聚反应^[4]等不同的光化学反应。     

叶绿素、染料体系光电效应的研究

叶绿素光电性质的研究有特殊意义.70年代开始国内外已有很多报道, 它们有整流、光导、光伏和光解水制取氢和氧等性质^[1-5].我们也报道过叶绿素a/聚乙烯醇夹层电池的研究^[6-8]。     

硝基磺酚C光度法测定蛋白质的研究

蛋白质的定量分析是生化研究、临床化验和食品检验等领域经常涉及的内容.以有机小分子作光谱探针测定蛋白质,如甲基橙^[1,2]、考马斯亮蓝G-250^[3]、溴酚蓝^[4]、溴甲酚绿^[5]和偶氮胂Ⅲ^[6]等已得到研究.     

二苯并噻吩及其氧化物与离子液体相互作用的理论研究

采用密度泛函理论方法比较了DBT/DBTO₂和[BMIM]⁺[PF₆]^-/[BMIM]⁺[BF₄]^-的相互作用。对最稳定的[BMIM]⁺[PF₆]^-、[BMIM]⁺[PF₆]^--DBT、[BMIM]⁺[PF₆]^--DBTO₂、[BMIM]⁺[BF₄]^-、[BMIM]⁺[BF₄]^--DBT、[BMIM]⁺[BF₄]^--DBTO₂进行了NBO和AIM分析。结果表明,DBT和[BMIM]⁺[PF₆]^-/[BMIM]⁺[BF₄]^-中的咪唑环彼此相互平行,NBO和AIM分析表明它们之间发生了π-π相互作用。H1'和H9'形成的F…H氢键有利于π-π堆积作用的形成。DBTO₂倾向于趋近C2-H2和甲基基团形成O…H相互作用;DBTO₂优先吸附在[BMIM]⁺[PF₆]^-/[BMIM]⁺[BF₄]^-。在模拟油中,[BMIM]⁺[PF₆]^-和[BMIM]⁺[BF₄]^-离子液体对DBTO₂的萃取能力大于DBT,其原因是可能是DBTO₂具有较大的极性和O…H与F…H的氢键作用。     

紫外光照射下ZnO超微粒子表面上的光反应

由于半导体超微粒子具有独特的尺寸量子化效应和表面效应^[1~6],它在利用太阳能光催化降解有机污染物,有机光合成及光电转化等领域中有着极其广泛的应用.目前,大量的工作集中在超微颗粒表面上有机物的光反应过程的研究^[7].     

植物生物分子的电分析化学研究Ⅷ.秋水仙碱的微分脉冲极谱行为及分析应用

秋水仙碱是近年来新发现的有前途的抗癌植物有效成分。秋水仙碱的测定方法,如容量滴定法^[1]、电位滴定法^[2]、紫外分光光度法^[3]、荧光分析法^[4]和高效液相色谱法^[5]等,手续均不太简便。电化学分析研究秋水仙碱主要有阳极伏安法^[6]和交流极谱法^[7],前者因使用固态电极,重现性较差。后者用非水溶剂作介质,灵敏度不高。     

反式聚苯乙炔的光电导

聚苯乙炔(PPA)是一种共轭高分子材料,具有较好的光电导性能。因反式PPA比顺式具有较高的光暗比,本文研究了反式PPA的光导和暗导特性,得到的光、暗导曲线基本平行,说明本征载流子和光生载流子的输运机制是相似的。在欧姆区的光导和暗导的活化能分别为0.24±0.03eV和0.58±0.03eV。     

钒氧酞菁的合成及其薄膜结构与光电性能的研究

自从60年前^[1]金属酞菁被发现以来,就引起人们的广泛兴趣,其原因主要在于它们在染料颜料、光化学、催化、和成像中的应用. 和许多其它酞菁衍生物一样,钒氧酞菁具有光导和半导体特性,这使得它在光电子学、电子成像、化学传感器、甚至于微电子器件中有潜在的十分光明的应用前景^[2]. 例如, 钒氧酞菁在电子成像体系中已成为有用的感光材料. 近年来,金属酞菁等有机材料的结晶薄膜开始不断地吸引人们的注意力. 人们考察了不同的金属酞菁如: 酞菁铜、酞菁铅、酞菁镍、和酞菁锡 等的光电导和光电压^[3]. 通常酞菁以几种不同的多晶异构体、即以不同的晶体排列结构方式存在. 因此,其光电特性不仅取决于分子中心的金属原子、而且取决于它们的晶体结构. 总之,值得我们研究钒氧酞菁薄膜的光电特性以及它与吸收光谱和薄膜晶体结构的关系.     

Cyclopropyl carbanions derived from esters of 2-phenylcyclopropylcarboxylic acids: Configurational stability and reaction with electrophiles

The base-catalyzed cis-trans isomerization of cis and trans-alkyl 2-phenylcyclopropylcarboxylates was studied in several aprotic solvents. It was found that contact ion-pain of the derived carbanion lithium salts were configurationally more stable than the solvent-separated ones. Reaction of either the cis or the trans esters with MeI, and the reaction of the cis ester with Ph₂C = O, resulted in the corresponding I-substituted derivatives having cis geometry only. This was explained as due to steric hindrance to elctrophilic attack exerted by the 2-phenyl group in the case of the trans substrate. The trans esters did not react with Ph₂C=O. Inhibition of the trans-to-cis isomerization of the carbanion salt of the trans substrate in presence of Ph₂C=O could lead to this result.     

Construction and investigation of photo-switch property of azobenzene-bridged pillar[5]arene-based [3]rotaxanes

Series of azobenzene-bridged pillar[5]arene-based [3]rotaxanes with different alkyl chain length of guest molecules were constructed by threading-endcapping method with alkylenetriazole as axile and tetrahydrochromene as endcapping group.The encapsulation of pillar[5]arenes were proved by highresolution mass,¹ H NMR and NOESY spectra.The photo-responsive property were examined by irradiation of the synthesized [3]rotaxanes with 365 nm and blue light LED,which caused trans to cis and cis to trans isomerization,respectively.Irradiation of corresponding model guest compounds without pillar[5]arene encapsulation resulted in near completely trans to cis and cis to trans isomerization,indicating the existence of pillar[5]arenes is the determining factor for the comprised photo isomerization efficiency.     

Konformation und physikalische daten von alkanen und cyclanen—V Dimethylcycloheptane

cis-trans-Isomeric dimethylcycloheptanes were prepared in great purity. The best method was found to be the ring expansion of definite alkylcyclohexanone followed by reduction. If tertiary cycloheptanols are dehydrated a rearrangement to 6-membered ring olefins takes place.

A consideration of densities, refractive indices and enthalpies of isomerization of the alkylcycloheptanes shows, that the twist-chair model of cycloheptane, which was established by Allinger and Hendrickson, is in agreement with the experimental values. All isomers with the exception of 1,1-dimethylcycloheptane and cis-1,2-dimethylcycloheptane have a quasi-diequatorial arrangement. The enthalpy of isomerization between cis- and trans-1,2-dimethylcycloheptane is 0·7 kcal/mole.     

二维界面上偶氮苯糖脂的光响应行为

设计合成了含偶氮苯基团的糖脂Gal-azo-Cn,通过Langmuir Blodgett(LB)膜、原子力显微镜技术对该糖脂在气液界面上的光异构化行为进行研究。实验表明,气液界面上的纯偶氮苯糖脂及与磷脂混合形成单分子膜的偶氮苯糖脂均具有反-顺、顺-反异构化行为。紫外光引起的异构化过程导致表面压力上升,但是由于二维界面上膜压的存在对其反-顺异构化行为有抑制作用,膜压越大,压力上升越小,黑暗环境中顺-反异构化过程则越快。对比纯偶氮苯糖脂的界面异构化行为,混合体系中磷脂分子与偶氮苯糖脂分子间的相互作用,对二维界面上糖脂的反-顺异构化有促进作用,提高了偶氮苯糖脂的反-顺异构化程度。磷脂-糖脂混合体系中,混合组分中含不饱和碳链的磷脂含量越高,膜的流动性越强,稳定性越差,对偶氮苯糖脂异构化行为的促进作用越弱。     

Trans-cis isomerization of an azoxybenzene liquid crystal

Trans-cis isomerization was investigated in a room temperature liquid crystal mixture of two azoxybenzene compounds. Experiments were performed on isolated molecules in dilute solutions and on the liquid crystal phase composed of the pure compounds. The absorption spectra of the trans and cis isomers were found to be similar to those of azobenzene compounds, as were the birefringence and order parameter of the nematic liquid crystal phase. The photo-optic properties were also similar in that irradiation by ultraviolet light caused the conversion from trans to cis isomers, while short wavelength visible light incident on these compounds resulted in the conversion from cis to trans isomers. The activation energy for thermal relaxation from the cis to trans isomer in the liquid crystal phase was determined to be (66±7) kJ/mole, which is less than for azobenzene in solution. While a photostationary state in a dilute solution with approximately equal numbers of trans and cis isomers was achieved, the nematic-isotropic transition of the mixture of the pure compounds decreased from 70°C to room temperature with a cis concentration of only about 12%. One unusual finding was that the photostationary concentration of trans and cis isomers due to irradiation with light of a specific visible wavelength depended on the starting concentrations of the two isomers, indicating that there may be a molecular conformation that is not photo-responsive and relaxes only thermally.     

Reactivity of ruthenium complexes with uninegative (X,S)-donor ligands (X = S,P)—II. Phosphine substitution in [Ru(S,S)2(PR3)2] derivatives. Crystal structure of trans-bis(O-ethyldithiocarbonate)bis(dimethylphenylphosphine)-ruthenium(II)

The complexes [Ru(S,S)₂(PPh₃)₂] [S,S = EtCOCS₂⁻, (CH₂)₄NCS₂⁻] react with a variety of tertiary phosphines with the substitution of triphenylphosphine and the formation of [Ru(S,S)₂(PR₃)₂]. The reaction occurs with the formation ofthe cis isomer, except for the complex with PMe₂Ph that gives rise to the trans isomer as the crystal structure shows. The effect of the different phosphines on the ruthenium complex is analysed in terms of the spectroscopic and electrochemical properties of the isolated compounds. The cyclic voltammetric studies of the cis complexes show that isomerization to the trans isomer occurs on oxidation. This isomerization is not observed in the trans-[Ru(S,S)₂(PMe₂Ph)₂] complexes that give rise to stable trans-ruthenium(II)/ruthenium(III) couples. In a similar way the diphosphine complexes afford a quasi-reversible cis-ruthenium(II)/ruthenium(III) process.     

Ozone interaction with conjugated polymers—II. Polyphenylacetylene

Free-standing films of cis-transoidal polyphenylacetylene, when treated with ozonized air at 1–2% by weight O₃ concentration, undergo a cis-trans isomerization induced by ozone as shown by electronic spectra. Moreover, the presence of the radical cation of polyphenylacetylene can be observed during ozone addition. The cis-trans isomerization is also confirmed by FT-IR spectra of polyphenylacetylene ozonized in solution. Hydroperoxidic groups, as well as peroxidic and aldehydic, are observed by FT-IR spectroscopy on ozonized polyphenylacetylene; in addition, ozonide groups are clearly present. The kinetics of ozonization of cis-transoid and trans-cisoid polyphenylacetylene was followed by electronic spectroscopy. The curves obtained as a function of ozonization time have a characteristic sigmoid shape. Polyphenylacetylene reacts more slowly with ozone than with the isolated double bonds of cis-1,4-polyisoprene, and thus it cannot act as an antiozonant.     

Pigment Yellow 101: A showcase for photo-initiated processes in medium-sized molecules

Pigment Yellow 101 (P.Y.101) is a fluorescent yellow pigment which exhibits a surprisingly rich photochemistry of several competing reaction pathways as revealed by recent time-resolved femtosecond experiments. Our elaborate quantum chemical investigations employing density functional theory (DFT) and time-dependent DFT (TDDFT) show that the observed fluorescence competes with excited state intramolecular proton transfer and trans–cis isomerization processes. Moreover, the experimentally observed spectral features of the complicated excited state dynamics can be assigned to stable trans-diol, trans-keto and cis-diol, cis-keto isomers on the ground and excited state surfaces. Still, due to its molecular size P.Y.101 poses a challenge to electronic structure theory and many problems occur in particular with respect to the excited state calculations. Thus, P.Y.101 serves also as an educative example for which TDDFT yields a reasonable vertical electronic spectrum, but fails in the prediction of excited state structures, when standard GGA or hybrid functionals with low fractions of Hartree–Fock exchange are employed. This failure is attributed to the charge-transfer failure of TDDFT.     

The use of trans-2,3-divinyl epoxides as precursors to carbonyl ylides

trans-2,3-Divinyl epoxides have been found to be good substrates for the generation of carbonyl ylides in CCl₄ and 145 °C. These ylides, to a limited extent, undergo isomerization to cis-2,3-divinyl epoxides, leading to the isolation of 4,5-dihydrooxepins. Of greater potential usefulness is the finding that these ylides can be efficiently trapped in an intermolecular sense by a dipolarophile, leading to dihydrofurans.     

Ab initio analysis of the conformational changes of the prolyl-proline model peptide

For- -Pro- -Pro-NH₂ is an ab initio model of the prolyl-proline sequence unit present in numerous peptides and proteins. Cis–trans isomerization of the peptide linkage is a crucial step in accessing the active conformation of several proline containing macromolecules.

The present study focuses on the flexibility of the five-membered pyrrolidine ring, which is considered to help other conformational changes as well as cis–trans isomerization. Ring flexibility is characterized by the pseudorotational amplitude, A, and the phase angle, P. Calculations are carried out at the RHF/6-31+G(d) level of theory. The choice of method and level of theory is further supported by single point DFT calculations.

In the course of NMR structure determination of peptides or proteins, proline residues present in the sequences need special attention. Because of the lack of an amide hydrogen, sequential assignment of proline is rather complicated. Furthermore, in solution state, peptide cis–trans isomers are almost always present. Ab initio study on the For- -Pro- -Pro-NH₂ model is a useful tool to discover the structural characteristics of the prolyl-proline sequence unit.