分子中的环识别算法

对于化合物结构自动解析系统来说,环的处理是必须的^[1~4],本文设计了环识别模块,该模块以从化合物的二维连接表出发,先获得化合物中的所有环,进一步得到最大环和最小环,并作为环约束,以增加ESESOC系统结构生成器的有效性。     

芳香性研究进展

综述了芳香性的概念,芳香性的判据和应用以及研究进展,随着量子理论和合成新的芳香环的迅速发展,芳香性含意也在深化和发展,芳香族化合物的应用范围日益扩大。     

稠环芳烃的化学通式以及其芳香性与休克尔规则的关联

为了阐明稠环芳烃的芳香性, 通过一个简单的数学模型推导出稠环芳烃的分子通式为C4R+2-IH2R+4-I。以此分子通式外推则可以很好地解释为什么任意一个稠环芳烃均符合4n+2的休克尔规则, 并且其中n=R-I/2。利用数学模型得到的这个分子通式提供了一种新的理解芳香性问题的科学思路。     

双环芳香性

本文按照Goldstein-Hoffmann的“链带模式”理论介绍了双环芳香性。同时,对(CH)_n长环离子的合成、结构与性质作了扼要的描述,它们包括双环[3.2.2]壬三烯基、双环[3.3.2]癸三烯基、双环[4.2.1]壬三烯基及双环[4.3.2]十一碳四烯基离子。     

C2BH3稳定性与芳香性的从头算研究

在密度泛函理论B3LYP/6-311 G(2df)水平上,对C2BH3异构体进行结构优化和简谐振动频率计算。结果表明C2BH3基态为平面环状结构(1A1,C2V)。分子轨道分析显示基态有一个垂直于分子平面、双电子占据的π分子轨道;其三元环几何中心核独立化学位移(NICS)为较大负值,这些表明基态分子具有较强的芳香性。在相同的理论水平上,本文最后详细地分析了基态的红外振动光谱。     

化学课堂教学有效性的评价研究

依据系统科学理论,探讨了课堂教学基元系统有效性(EfPrS)的含义;运用项目分析、探索性因素分析和验证性因素分析方法,开发了EfPrS的评价量表,并得到了影响EfPrS的5个最主要因素,分别为:"时间利用的合理性(RUT)" "教学行为链的实施质量(QTBC)" "匹配度(MD)" "资源和手段的使用质量(QUR&T)"和"基元内容的合理性(RPrC)";运用回归分析方法建立了EfPrS与5个影响因素之间的线性回归方程,并得出QTBC是影响EfPrS的最主要因素;运用聚类分析和判别分析方法得到了课堂教学基元系统高效、中效和低效的边界值。     

环双(对-蒽基-对草快)的分子识别与谱学性质

环双(对-蒽基-对草快)是一种新型的缺电子大环仿生主体, 分子识别是其最重要的应用之一. 考察主体对一系列客体分子如水、氨、醇及杂环等的识别能力, 用密度泛函理论(DFT)中的B3LYP/3-21G基组对主客体复合物的结构进行优化. 在B3LYP/6-31G(d)水平上进行单点能计算, 校正后得到复合物的结合能. 用B3LYP/3-21G方法计算13C和3He化学位移. 结果表明, 主体对客体分子的识别主要靠客体上的杂原子与主体上的氢原子之间的氢键进行. 复合物的稳定化能受氢键的数目和距离影响. 氢键的形成导致部分复合物LUMO与HOMO能隙增大, 同时导致与氢键相连的C—H键上C原子的化学位移向低场移动. 复合物的芳香性与其结合能的大小及结合方式有关. 主体的芳香性因其与客体之间的弱相互作用而提高, 但太强的相互作用及客体在主体空腔内都将影响主体的环电流, 从而削弱其芳香性.     

关于反应分子数定义的讨论

There are two different views on the definition of reaction molecularity in physical chemistry textbooks and related literatures so far. We give a deep discussion about this conception herein. Starting with the development of chemical kinetics and the definition of elementary reaction and state-state reaction, we clarify that elementary reaction and state-state reaction are the conceptions belonging to macro-and micro-systems, respectively, and reaction molecularity is also belonging to micro-conception. Based on this conclusion, we think that the more reasonable definition of reaction molecularity should be "the number of chemical particles that take part in a state-state reaction (or an elementary chemi-physical reaction) as a reactant".     

分子内环加成的甾体全合成

近年来,分子内环加成反应已广泛用于甾体化合物全合成,其主要一步是由取代的苯并环丁烯热裂而成的5,6-二亚甲基-1,3-环己二烯发生区域专一和立体选择性的环加成反应,构成甾体骨架。现在用此法已合成了一系列消旋和光学活性的甾体化合物。     

分子的模糊对称性

将模糊数学方法引入对分子对称点群的研究,建立描述具有不完整分子对称性的模糊点对称群(集合).建立具有模糊对称性分子轨道的模糊表示及其模糊特征标(模糊广义宇称).通过对典型的线状分子、平面分子以及非平面的立体分子等进行分析,展示了一个新的理论化学园地.初步探讨了具有模糊对称性的动态反应体系.从模糊对称性出发,探讨了分子轨道对称守恒原理的半定量特征.     

自然键轨道方法研究分子的芳香性

用自然键轨道方法研究了环状共轭分子的芳香性,提出了用自然键轨道的准离域能作为量度分子芳香性的标准,用INDO方法和DV-Xα方法计算了20多个环状有机或无机分子的自然键轨道的准离域能。根据准离域能标准判断的分子芳香性大小顺序与文献的结果基本一致,表明本文提出的芳香性量度标准的有效性和可用性。     

“Organic Metals”—The Intermolecular Migration of Aromaticity

The electrical conductivity of a wide variety of organic materials is reviewed and a comparison made between those materials which transport charge efficiently and those that do not. This comparison reveals that the most efficient conductors contain molecules (a) whose radical ions form a new aromatic sextet upon one-electron oxidation or reduction and (b) whose aromaticity can migrate by mixed-valence interaction. The electrical data are presented in light of the chemistry of these materials and the importance of chemical bonding interactions in the electron transport process. Several new examples are discussed and directions for further research explored.     

NiTi过渡金属团簇的结构和芳香性的理论研究

在B3PW91/6-311+G(d)计算水平上, 计算并讨论了Ni₄Ti₂, [Ni₄Ti₂]²⁺, [Ni₄Ti₂]^2-与Ni₄Ti₄, [Ni₄Ti₄]²⁺, [Ni₄Ti₄]^2-团簇的几何结构和芳香性. 在构型优化过程中得到了Ni₄Ti₂(D_4h), [Ni₄Ti₂]²⁺(D_4h), [Ni₄Ti₂]^2-(D_4h)和Ni₄Ti₄(D_2h)4个稳定构型, 发现当引入上下2个Ti原子后, Ni₄环成为了平面正方形构型. 核无关化学位移(NICS)计算结果表明, Ni₄Ti₂(D_4h)与Ni₄Ti₄(D_2h)的NICS值为正, 而[Ni₄Ti₂]²⁺(D_4h)和[Ni₄Ti₂]^2-(D_4h)的NICS值为负, 且[Ni₄Ti₂]^2-(D_4h)的NICS值更负. 同时还发现, 由s与d轨道参与形成的反磁性环流是引起[Ni₄Ti₂]²⁺(D_4h)和[Ni₄Ti₂]^2-(D_4h)具有较大芳香性的主要原因; 其中Ti原子主要提供d_z²与s轨道, 而Ni原子主要利用其d_z²与d_x²-y²轨道形成正方形环, 它们之间构成了球状的d轨道环流, 且[Ni₄Ti₂]²⁺(D_4h)和[Ni₄Ti₂]^2-(D_4h)中还有非常明显的π轨道环流.     

硒芳香杂环化合物的光谱和电化学性质

用紫外光谱，荧光光谱和循环伏安法研究了含硒芳香杂环化合物（苤硒脑）在不同溶剂中的谱学和电化学性质，对不同分子结构或取代基的苤硒脑化合物的性质进行了比较，并初步探讨了溶剂对苤硒脑化合物谱学性质的影响规律。     

Theoretical Analysis on Magnetic Properties of Conjugated Organic Molecules Containing Borepin

Theoretical study about the magnetic properties of conjugated organic molecules containing borepin with π current density was carried out. 1-(2,4,6-Trimethylphenyl)borepin moiety is the center and other different groups are situated on the both β sides, which are named molecules 1-12 as theoretical model in order to establish the relationship between aromaticity and geometry variation of borepin. The optimized molecular structures of molecules 1-12 are almost keeping planar and the C2-C3 bond length of borepin turns longer from molecule 1 to molecule 12. Different borepin-annulated ring could change the conjugated effect of π-electron between borepin and these borepin-annulated rings. Moreover, the molecule presents antiaromaticity, in other words, the molecule became unstable when the C2-C3 bond length of borepin extended more than ca. 0.1417 nm. But the β position fragment and substituent groups of borepin are not affected in this case, they are still steady. However, the central borepin ring current is counteracted by symmetrical overlap of it with affiliated borepin-annulated ring current. Hence, the central borepin ring breaking would be liable to occur. These molecules have higher vertical ionization potentials(VIPs) and lower vertical electron affinities(VEAs), which suggests that these molecules could easily exist in anionic form.     

The Adverse Effect of Benzannelation on the Aromaticity of Oxocinyl Anion: A Combined Experimental and Theoretical Study

A synthesis of 2H‐1‐benzoxocin from readily available compounds was accomplished. The potentially ‘aromatic’ π‐excessive systems 2H‐1‐benzoxocinyl and 6H‐dibenz[b,f]oxocinyl anions were generated from their corresponding conjugate acid precursors 7c and 8 , respectively. It was found that 2H‐1‐benzoxocinide 3d lacks the type of π‐frame stability associated with the parent 2H‐oxocinide 1d and that the dibenzo analog 5b is more unstable than 3d . Both 3d and 5b undergo rapid structural reorganization to form their corresponding stable isomeric anions. We were able to characterize the proton‐quenched products of these anions as the ring‐opened structures 15 and 18 , respectively. ¹H‐NMR and an ab initio calculation at the 6‐31g* level indicated that, unlike the ‘aromatic’ parent 2H‐oxocinide 1d and the aza analog 3c, 3d incorporates a non‐planar oxocinyl ring in which the negative charge is primarily localized on the pentadienyl moiety of the ring, but also partial delocalization of π‐electron density onto the benzene ring occurs.     

高分子基础实验的优化与改革

为适应高分子材料与工程专业实验分层次教学改革的要求,结合我院高分子材料与工程专业的具体实际,在教学内容设计中融入科学、节约、环保的理念,对高分子基础实验体系、内容、组织与运行、教学方法与手段进行了整体优化和改革。使实验成本得到降低,污染物明显减少,实验教学效果得到显著提高,实现了高分子专业基础实验教学效益的最大化。     

Determination of the Fractal Dimensionality of an Assembly of Adsorbed Molecules

A method is proposed for determination of the fractal characteristics of nanodimensional surfaces using calculation of the probability measure for a set of adsorbed molecules. By this method on the basis of the experimental adsorption isotherm of methane on activated charcoal the fractal dimensionality of the investigated sample was determined.     

Substitute Effect on the Structure,Stability of Valence Isomers and Aromaticity of 1‐H‐Boratabenzene

Density functional theory (B3LYP) calculations were performed on the Me and F substituted valence isomeric forms of 1‐H‐boratabenzene. The calculations revealed that the planar benzene analog is the lowest energy isomer. Its aromaticity is analyzed in the light of the nucleus‐independent chemical shift (NICS) and shows that aromaticity increases in F substituted, but decreases in Me substituted. These calculations indicate substitution of BH with BMe and BF doesn't cause significant variation in bond length.