靛蓝衍生物的光异构化

合成了六个N,N′-双酰基取代的靛蓝衍生物,研究了这类染料的光致变色的宏观动力学。用不同的波长,可以使反式异构体转化为顺式异构体,或使顺式异构体转化为反式异构体。讨论了异构化反应的机理。     

苯二胺双电荷离子的电荷分离和电子捕获诱导解离谱研究

本工作用电荷分离(CS)谱和电子捕获诱导解离(ECID)谱研究了三种苯二胺异构体的双电荷分子离子在气相中的结构和反应。三种异构体双电荷离子的电荷分离反应和电子捕获诱导解离反应有相同的反应通道。通过测量不同反应通道的动能释放, 推测出了双电荷离子解反应过渡状态的结构。另外, 三种异构体可用ECID谱来区分。     

分子模拟法研究锌离子在Aβ多肽聚合过程中的键合模式

脑部淀粉样β多肽(Aβ)的纤维化沉积是阿尔茨海默病主要的病理特征之一. 体外实验发现在生理浓度条件下锌离子有很强的诱导Aβ聚合的能力. 为了探讨锌离子的诱导机理, 文中通过分子模拟方法研究了在不同环境下锌离子和Aβ(10-21)的键合模式. 首先分别建立了由1, 2, 4, 12条Aβ多肽组成的不同聚合状态的分子体系, 然后在参照大量实验结果的基础上将锌离子有选择地放置在Aβ多肽的不同位置, 同时考虑锌离子配位数为2和4两种配位情况, 最后通过对结合体系进行能量最小化来寻找锌离子在Aβ多肽上的最佳键合位点. 计算结果显示在可溶键合模式中, 锌离子被包容在由组氨酸残基His14的咪唑Nτ、多肽主链上的羰基氧以及两个水分子氧形 成的四面体络合物中; 在纤维化过程中, 锌离子可能通过His13(Nτ)-Zn²⁺-His14(Nτ)桥键将相邻的、不同Aβ多肽交叉连接形成纤维束. 以上结果将对实验揭示锌离子参与下Aβ多肽的变构以及斑点核形成过程提供有益的启发, 并对在分子水平上研究阿尔茨海默病机理具有切实意义.     

(μ-苯硫)(μ-烃硫)六碳基二铁络合物的合成及波谱研究

本文合成了(μ-PhS)(μ-RS)Fe_2(CO)_6系列的九个铁硫原子簇络合物,考察并确定了RX的结构对亲核取代反应活性的影响及络合物可能的空间异构体和比例.对由C≡O各向异性效应及硫上孤电子对的空间取向所引起的异构体中SCH_3、SCH_2δ值的规律变化进行了初步讨论.     

四氢咪唑取代亚甲基β—二酮质谱碎裂机理的理论研究

理论计算非常适用于气相离子化学研究[1，2]，它与质谱实验相结合可以识别许多非常规的和以往所不知道的自由基离子，也可以提供反应能和机理方面的信息，有助于探讨可能的异构化过程和不同异构体结构的相对稳定性．离子／中性复合物（离子和中性碎片通过静电引力结合在一起）[3]作为有机离子质谱单分子碎裂的重要中间体已被越来越多的理论和实验结果所证实[3，4]．串联质谱低能碰撞诱导解离和同位素标记技术的实验结果表明[5]：四氢咪唑取代亚甲基β-二酮分子结构中氮原子上氢表现出不同活性，其气相单分子碎裂经历了离子／中性复合物的中…     

2-(2′-羟苯基)苯并噁唑氨基衍生物电子结构和光谱性质的理论研究

采用量子化学方法优化了间位和对位2-(2′-羟苯基)苯并噁唑氨基取代衍生物(4-AHBO和5-AHBO)基态的第一单重激发态所有可能的稳定构型, 分析了这些异构体在不同溶剂中的相对稳定性. 利用含时密度泛函理论(TDDFT)的不同泛函, 计算了4-AHBO和5-AHBO各异构体在溶剂中的吸收与发射光谱, 考察了它们的电子结构和光谱特征. 结果表明, 4-AHBO(5-AHBO)的双荧光不是由同一种异构体发射的, 而是来源于不同异构体的发射: 长波区的荧光由酮式构型发射, 短波区的发射则可能由四种醇式异构体共同产生. 另外, 也解释了5-AHBO在质子溶剂中光谱异常的原因, 分析了不同氨基取代位和溶剂极性的变化对各异构体构型、光谱性质及电子结构的影响. 理论预测的光谱与实验结果一致.     

顺二氨二水合铂(Ⅱ)离子与半胱氨酸等的络合反应——电位法及分光光度法研究

用电位滴定法及分光光度法研究了顺二氨二水合铂(Ⅱ)离子与半胱氨酸、蛋氨酸及谷胱甘肽的络合反应.用电位滴定法测定[(NH_3)_2PtA](A 为氨基酸)型混合配体络合物的形成常数β,测得 A 为半胱氨酸及蛋氨酸时,1gβ分别为7.55及8.70.按(?)=0.5处 pA 计算谷胱甘肽络合物的最可能1gβ为9.00.用 Job 分光光度法测得结果与之符合.据此讨论了络合物的可能结构.在所有情况中,硫可能是优先配位原子.     

双8-羟基喹啉端开链冠醚金属络合物的光物理性质

设计合成了双8-羟基喹啉端的开链冠醚QP3Q,研究了金属离子铝或锌与其形成络合物的组成和发光性质,并测定了络合物的激发态寿命.这些络合物在溶液中有较高的荧光量子产率,所得到的络合物固体具有较强的蓝光发光性能.结果表明,有可能通过QP3Q与不同离子形成的络合物得到不同发光波长的发光材料.     

二甲苯异构体及其质子络合物的量子化学计算

利用量子化学的CNDO/2法对一系列二甲苯异构体及其质子络合物进行了计算,结果表明,它们的稳定性具有下列次序:定域σ-络合物>定域π-络合物>二甲苯异构体>CH₃离域π络合物并且进一步阐明了二甲苯异构体的异构化能、电离能、酸碱性、质子亲合势、亲电子反应等物理化学性质以及间二甲苯在酸性催化剂中的异构化机理。     

手性双膦配体的合成及其在不对称反应中的应用

近三十年来,人们对光学异构体在药物、食品添加剂、昆虫信息素、农药和香料等领域中的应用做了广泛地研究,结果表明,在大多数情况下,光学异构体的性质不尽相同,其差别表现为1>生物活性不同;2>转运机制不同;3>可能的代谢途径不同。这样如何获得一种单一构型的光学异构体就成为化学家研究的重点课题。不对称反应的发现和近年来取得的成就为获得单一构型的光学异构体提供了一条简捷而经济的途径。手性过渡金属络合物催化的不对称反应人     

偏最小二乘紫外分光光度法同时测定丁烯二酸的顺反异构体

将偏最小二乘法用于紫外分光光度分析,在pH=1.4的磷酸溶液中,同时测定了丁烯二酸的顺、反异构体。确定了测定的最佳波长范围为190～268nm;测得23个混合标样的吸光度值用于建立模型,顺、反丁烯二酸的浓度范围为3.0～14.0mg/L和1.0～13.0mg/L。所建立的测定二者模型的相关系数分别为0.9951和0.9983;平均回收率分别为100.8%和100.7%;均方根误差(RMSE)分别为0.3667和0.2233;预测相对误差(REP)分别为5.05%和3.49%。对3个批次反丁烯二酸样品的测定结果与高效液相色谱法的测定结果进行比较,经成对t检验表明,两种方法的测定结果无显著性差异。     

1,4-二(2-萘基)的环乙烷的合成及顺, 反异构体的结构鉴定

Hassel和Barton成功地研究了环己烷的构象变化,为研究单糖、多糖以及甾体等天然化合物的结构和性质奠定了基础。近年来的研究表明,含环己烷环的液晶化合物中六员环的构型直接影响液晶的性质。例如,反式1-烷基-4-(对-氰基)苯基环已烷可以形成液晶,而顺式异构体分子不能有序排列。De Schryver     

FT-IR and FT-raman spectroscopy study of the cyclic anhydride intermediates for the esterification of cellulose: III. Cyclic anhydrides formed by the isomers of cyclohexanedicarboxylic acid

Multifunctional carboxylic acids have been used as crosslinking agents for cotton and wood pulp cellulose. In our previous research, we found that a polycarboxylic acid esterifies cellulose through the formation of a 5-membered cyclic anhydride intermediate by the dehydration of two carboxyl groups. In this research, we studied the formation of cyclic anhydride intermediates by different isomers of cyclohexanedicarboxylic acid (CHA) so that we can elucidate the effects of molecular structure on the formation of the anhydride intermediates. We found that both cis-and trans-1,2-CHA form 5-membered anhydride intermediates when temperature reaches their melting points and that cis-1,2-CHA forms the cyclic anhydride at temperatures lower than does trans-1,2-CHA. 1,3-CHA forms 6-membered cyclic anhydride at temperatures much higher than its melting point. The formation of a 5-membered cyclic anhydride intermediates takes place at temperatures lower than that of a 6-membered anhydride. This is probably the main reason why those polycarboxylic acids with their carboxylic acid groups bonded to the adjacent carbons of the molecular backbones are more effective crosslinking agents for cellulose than those with their carboxylic groups bonded to the alternative carbons. No formation of cyclic anhydride was found for 1,4-CHA. The formation of a five-membered cyclic anhydride was accelerated by monosodium phosphate, which is used as a catalyst for the esterification of cotton cellulose by polycarboxylic acids.     

Cyclopolymerization. VII. The 13C NMR Spectra of Cyclopolymers Obtained from N,N-Diallyamines

Pulsed Fourier transform ¹³C natural abundance nuclear magnetic resonance spectroscopy has been used to determine the structures of the polymers formed by the radical-induced cyclopolymerization of N-substituted-N, N-diallylamines and N-methyl-N, N-bls(2-alkylallyl)-amines. The polymers of N, N-diallylamines all contain cis-and trans-substituted pyrrolidine rings in the ratio 5:1. The polymers of N-methyl-N, N-bis(2-alkylallyl)amines give complex spectra due to the presence of both cis-and trans-pyrrolidine and -piperidine rings, but the difference in chemical shifts of the N-methyl signals from the different structural types allows the spectra to be analyzed.     

Reactivity studies of a disilene with N2O and elemental sulfur

In a previous contribution, we have reported on a convenient and high yield synthesis of the disilene trans-[(TMS)(2)N(η(1)-Me(5)C(5))Si═Si(η(1)-Me(5)C(5))N(TMS)(2)] (2). Herein, we show the reactions of 2 with N(2)O and S(8). The former reaction affords two isomeric (cis- and trans-) dioxadisiletane ring compounds. To the best of our knowledge, this is the first report where both cis-and trans-isomers are isolated from the same disilene precursor and characterized structurally by single-crystal X-ray diffraction (XRD) studies. The reaction of 2 with elemental sulfur yields only the trans-isomer. To investigate this dissimilar reaction pattern exhibited by 2, computational studies were performed. Density functional theory (DFT) calculations showed that the two dioxadisiletane ring isomers are isoenergetic, with the trans isomer being slightly more stable than the cis counterpart, by 3.3 kcal/mol, while that is not the case with sulfur. All the isolated compounds are characterized by single-crystal XRD studies, multinuclear NMR spectroscopy, and electron ionization-mass spectrometry (EI-MS).     

STUDIES ON ORGANOSILICON REACTIVE INTERMEDIATES (Ⅴ)~*——STEREOSPECIFIC ADDITION OF CYCLOPROPYLPHENYLSILYLENE TO OLEFINS

This paper reports that cyclopropylphenylsilylene (1) is obtained by photolysis of 2-cyclopropyl-2-phenylhexamethyl-trisilane. 1 added stereospecifically to cis-and trans2-butene gives the corresponding siliranes. Opening of the sillranes by methol also occurs in stereospecifically cis fashion.     

对环芳烷二氯化产物组成的GC—MS表征

对环芳烷([2,2]Paracyclophane,简称PCP）是指苯环对位桥联的化合物,PCP及其氯代PCP的重要用途是通过升华、裂解、聚合等步骤沉积于物体表面形成聚合膜,该聚合膜具有透湿和透气小、抗化学腐蚀和抗辐射等优良性能[1,2].     

DFT Investigation on the Trans-cis Photoisomerization of Pentamethine Cyanine Dye Model Molecule

The trans-cis photoisomerization of pentamethine cyanine dye (Cy5) has been theoretically investigated by the analysis on an analogical molecule model. All possible isomers have been searched by rotating the different bridge C-C bonds of the model. The relative stability of the isomers for the ground and first excited states as well as the corresponding excitation mechanism has been envisaged by DFT and time-dependent DFT method. The results show different conjugation degree of the isomers resulting in different absorption energy upon the different C-C bridge bond rotation. From the analyses of electronic density distribution of the frontier orbitals, it is predicted that there is charge transfer besides the π-π* excitation for the cyanine dye model, which makes the mechanism and photo-properties different form those of other conjugated molecules.     

The maximum hardness and minimum polarizability principles in accordance with the Bent rule

Energies, hardness values and polarizabilities for different isomers of SF₄, SF₄O molecules and a family of PCl_xF_5−x, (x=1,2,3,4) compounds are calculated at the density functional level of theory (B3LYP) using different basis sets (6-31G**, 6-311G**, 6-31++G and 6-311++G). For all molecules and in all cases the Bent rule is confirmed with the stability orders, which is obtained from the calculated energies. It is also found that for each molecule the isomer in which the more electronegative atom occupies the axial position has maximum hardness; and therefore according to the Maximum Hardness Principle (MHP), it must be the most stable isomer. This result is consistent with the Bent rule, but for some cases in which there are more than two isomers, the obtained trends for the stability are not in accordance with this rule. On the other hand, since the calculation of dipole polarizability is very sensitive to the quality of the selected basis set, only for those calculations in which diffuse basis sets are used the obtained trends of stability from the Minimum Polarizability Principle (MPP) are the same as those which are predicted from the Bent rule. It seems that when there are more than two isomers for a molecule both the MHP and MPP can only predict the most stable isomer and cannot predict the correct trend for the stability of the isomers.     

Vibrational spectroscopic study of rotational isomerism in O,O-dimethylphosphorodithioic acid

In this paper, the IR and Raman spectra of (CH₃O)₂P(S)SH have been studied at room temperature and at lower temperature. It is found that the P = S stretching vibrational band consists of four sub-bands, which shows that there are four rotational isomers for (CH₃O)₂P(S)SH. With the aid of computer we have separated the P=S bands and measured the relative intensities of each sub-band at different temperatures, so the relation of interconversion between isomers was obtained. Moreover, there exists intermolecular hydrogen bond in this compound, which will impede the rotation of S-H about P-S bond. Therefore, the interconversion of isomers results only from the rotation of O-CH₃ about P-O bond.