我国光化学研究的进展及展望

本文对我国开展光化学研究的历程和目前光化学研究的现状进行了简单的介绍,并对今后几年光化学的发展进行了展望.     

多原子体系非绝热动力学的近似理论方法

非绝热动力学普遍存在于光物理和光化学过程中。描述非绝热跃迁需要处理电子-原子核间的相互耦合运动。由于计算量随体系尺度增大剧烈增长,准确的量子动力学计算目前只适用于描述小分子体系。为了研究多原子分子体系的非绝热过程,近年来发展了一些基于量子-经典动力学近似方法。本文将对典型的这类方法包括经典Ehrenfest方法、面跳跃方法、基于Wigner表示的混合量子-经典方法进行简要的介绍,并讨论如何将量子-经典动力学方法与电子结构从头算手段相结合,模拟非绝热过程。重点阐明各种方法的基本思想和优缺点,并对该领域的发展进行展望。     

有机光化学研究的现状

本文综述了有机光化学的新进展和研究现状。介绍了激发态行为的研究方法,激发态的化学活性,扩散控制的激发能迁移,重要的有机光化学体系,激光化学,生物光化学,有机金属光化学和太阳能的贮存。对许多有价值的课题,作了比较粗略的论述。     

核酸光化学生物学

光敏感基团作为光化学开关被广泛应用于各种生物过程的光调控中。特别是过去十几年内,核苷酸、寡聚核苷酸和DNA/RNA的光敏修饰策略得到了长足的发展,并在细胞信号传导和靶基因的功能调控等诸多生物学研究中发挥重要的作用。本文主要针对常用的光敏感基团、光敏感核酸及其化学生物学研究进展进行简要综述,并对未来核酸光化学生物学的研究进行了展望。     

我国光化学研究的现状和展望

我国的光化学研究自1978年以来取得了蓬勃的发展和长足的进步。本文扼要地介绍了研究工作发展的简况,指出,我国的光化学已从起步时那种比较侧重注意具体合成方法和具体反应的研究水平,提高到对机理、对光化学和光物理中一些基本现象和基本运动规律研究的较深入的阶段,并进而发展为有明确应用背景和与高技术研究及开发密切相关的这样一种基础和应用并重的新研究格局。文章指出我国的光化学研究将会继续以较快速度发展,并以崭新姿态进入2000年。     

新型污染物多溴联苯醚和氰尿酸的光化学降解

由于在环境中的广泛分布和难降解特性,多澳联苯醚和氰尿酸这两种环境污染物近年来得到了广泛的关注.光化学方法能够成功降解这两种新型污染物.本文综述了使用光化学方法降解多溴联苯醚和氰尿酸的最新研究进展.介绍了在有机溶剂中和颗粒物表面多澳联苯醚的光化学分解,重点对二氧化钛光催化还原降解多溴联苯醚的反应途径及其机理,以及二氧化钛光催化分解氰尿酸的研究进行了总结,最后对光化学降解多溴联苯醚和氰尿酸的发展方向进行了展望.     

杂多蓝的结构及其光化学研究进展

本文介绍了关于杂多蓝(HPB)的结构及其光化学的最新研究进展,特别对新型结构HPB的合成、电子结构的计算化学、光致还原反应制备新型纳米金属材料、有机-无机光致变色复合薄膜、HPB对半导体材料的协同与敏化作用、以及特殊结构的HPB在光化学反应中的应用重点进行了阐述,并就合成新型结构杂多酸进而调变杂多蓝性质,及它们在光化学领域中的应用进行了展望。     

光敏离子载体——一类功能性超分子光化学体系

简要介绍了光敏离子载体——一类可用于识别、检测、运输和释放金属离子的超分子光化学体系的工作原理及其在生物、化学等方面的广泛应用     

光化学降解溶解有机物及其对生物过程的影响

溶解有机物对控制海洋和淡水水生系统的化学、生物和物理特性有重要的影响.光化学降解溶解有机物改变了生态体系的溶解有机碳、有机物的分子量及光学特性,并且产生复杂的反应性氧化合物、二氧化碳、一氧化碳、小分子量的有机酸、氨基酸、二硫化碳等,对生物过程有重要的影响.本文简要综述了光化学降解溶解有机物的过程机理及其对生物过程的影响.     

石墨烯的光化学修饰方法

石墨烯是由sp2杂化碳原子组成的具有蜂窝状结构的二维原子晶体.石墨烯的共价化学修饰是石墨烯研究领域的一个新的热点,也是石墨烯材料的表面改性和能带调控、以及合成新型二维石墨烯衍生物的重要途径.完整的二维蜂窝结构和离域大π键使得石墨烯的化学性质非常稳定,难以通过常规的化学反应获得高效的表面修饰,这是石墨烯共价化学的主要挑战.近年来,我们发展了一系列基于光化学原理的石墨烯共价修饰方法,利用光化学过程产生的活性自由基实现了石墨烯的高效共价加成和氧化反应,为石墨烯的光化学能带工程奠定了理论和实验基础.本文将以这些研究成果为主线,系统地阐述石墨烯的光化学修饰方法及其二维反应特性,并对该领域的未来发展趋势和所面临的挑战进行简要的展望.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.