Correlation of bond metallicity measures to electronegativity for binary oxides

We have investigated alkali, alkaline‐earth, and rutile binary oxides within density functional theory (DFT) and Bader's atoms‐in‐molecules theory, focusing on properties of bond and ring critical points, and their relations to band gap and Pauling electronegativity. We find linear relations of kinetic energy density, electron density, and the gap divided by kinetic energy density at the bond critical points to the difference of Pauling electronegativities of the cation and oxygen anion. At the ring critical points of rutile compounds, we also find that some bond metallicity measures are linearly related to the difference of electronegativities. This study extends our knowledge about the relations between bond critical points, band gap, and electronegativity, but also shows for the first time a quantitative relation between quantities at the ring critical points and global properties of the compounds.     

价电子均衡电负性及其应用

提出一种不同于传统方法的价电子均衡方法来计算均衡电负性,包括分子电负性、基团电负性和原子电荷. 用分子电负性对烷烃和单取代烷烃分子的第一电离能进行关联,用基团电负性对某些分子的¹H NMR谱化学位移进行关联,用原子电荷对脂肪族胺、醇和醚分子的气相碱性进行关联. 所得各回归方程均有良好的相关性. 同时还在价电子均衡方法的基础上对Sanderson方法和Bratsch方法进行了修正,用于关联上述各性能,结果表明比相应的原方法更为有效.     

利用石英增强光声光谱技术在2.0μm处实现高灵敏CO_2检测的实验研究

基于石英增强光声光谱技术,以中心波长为2.0μm的窄线宽分布反馈式半导体激光器(DFB)为激励光源,采用波长调制及二次谐波解调技术通过改变激光器工作电流实现波长扫描完成了痕量CO2气体检测系统,并通过优化实验参数确定了常压下激光最佳调制深度,实现了高灵敏CO2浓度的检测。通过改变待测气体中的水汽浓度,研究了水汽对CO2气体探测结果的影响,结果显示在水汽浓度低于0.2%范围内,CO2气体光声信号随H2O浓度的上升而明显增强,当浓度高于此值后,H2O浓度的增加对CO2光声信号的增强作用几乎维持不变。数据显示,常温常压下H2O分子通过提高分子弛豫率最多可将二氧化碳R16吸收线的光声信号幅值提高约2.1倍。优化后的装置可以很好的实现大气中CO2浓度的检测。该装置获得的最小探测灵敏度为19ppm(1σ,300ms积分时间),相应的归一化噪声等效吸收系数为4.71×10-9 cm-1·W·Hz-1/2。     

取代基效应定量研究新进展

综述了最近20多年有机化学取代基效应定量研究所取得的诸多新进展.主要内容包括：（1）电负性均衡原理得到普遍认同并用于计算分子中电荷分布和基团的诱导效应,分子电负性计算方法在几何平均法、调和平均法、加权平均法的基础上又提出了价电子均衡方法,进一步扩展了电负性均衡原理的应用范围.（2）试剂亲电、亲核能力的实验测定,提出了以二苯甲基正离子和醌甲基化合物等作为参考化合物的标定方法,其研究范围被扩展到气相条件、有机金属反应和自由基体系,得到一系列试剂的亲核参数N和亲电参数E.理论上提出亲电性指数和亲核性指数的概念及其定量计算公式,并对实验测定参数和理论计算指数之间的关系进行了深入研究.（3）极化效应参数从最初的经验方法,进而采用量子化学方法计算,再用统计方法提出了烷基极化效应指数PEI和基团极化效应参数PEIX,被广泛用于解释和估算有机化合物的气相酸碱性、电离能、生成焓、键能、反应速率、水溶解性和色谱保留值.（4）直接由取代苯的紫外光谱吸收能量计算得到的取代基激发态参数exCC,不同于取代基在分子处于基态的极性参数和自由基状态下的自旋离域效应参数,该参数用于对位二取代苯、取代二苯乙烯、二取代氮苄叉苯胺等多类有机化合物紫外光谱的定量相关,结果良好.（5）立体屏蔽效应的提出区分了传统的三种立体效应.在羰基与亲核试剂加成反应立体选择性定量表示,提出了立体选择性指数Ci;在表示基团对反应中心表面积屏蔽的定量提出了屏蔽参数SR,进一步基于反应中心体积被屏蔽的角度提出了拓扑立体效应指数TSEI,这些参数在分子内二面角、反应的立体选择性、烯烃和烷基苯的生成焓、咪唑离子液体的酸性以及烷烃与羟基自由基的反应速率等方面得到良好的应用.此外,论文还对有机化学取代基效应定量研究中值得进一步深入探索的领域和问题提出了建议和展望.     

REACTION OF (2-BENZOTHIAZOLYL)-SULFENAMIDES WITH P-CONTAINING REAGENTS

Abstract

The title reaction was investigated to find that only substitution reaction on amino group occurred when (2-benzothiazolyl)sulfenamides 1 reacted with P(NR₂,)₃, whereas the treatment of 1 with (RO)P(NR₂,)₂, gave derivatives of phosphorodiarnidothioic acid together with 2-alkylthiobenzothiazole and its isomer in addition to substitution products, and no substitution products obtained when N-substituted analogues of 1 were treated similarly.     

Theoretical study of novel porphyrins bearing electron donor–acceptor groups

This research project is focused on molecules that comprise a series of asymmetrically A₃B‐type meso‐substituted free‐base porphyrins and their related Zn‐metalloporphyrins. A and B were taken as electron‐donor and electron–acceptor groups. Full geometry optimizations without symmetry constrains were performed with B3LYP/6‐31G(d,P) methodology. Time‐dependent density functional theory calculations of the optimized structures indicate that there is a good agreement with the available experimental results. The highest occupied molecular orbital–lowest occupied molecular orbital (LUMO) gaps (ranging between 2.62 and 2.80 eV) are similar to those reported before for other porphyrins (2.29 eV). Also, the LUMO is situated close to the conduction band of titanium oxide, increasing the possibility of a charge transfer process. As porphyrins may act as electron transfer systems, the electron donor–acceptor capacity of these systems is characterized using two parameters; electrodonating (χ?) and electroaccepting (χ+) electronegativity. The main goal of this investigation is to analyze the electronic structure and the donor–acceptor properties of these porphyrins to see if these compounds could be useful for further applications related to the design of solar cells. © 2012 Wiley Periodicals, Inc.     

Fast tools for calculation of atomic charges well suited for drug design1

Two novel approaches to construct empirical schemes for partial atomic charge calculation were proposed. The charge schemes possess important benefits. First, they produce both topologically symmetrical and environment dependent charges. Second, they can be parameterised to reasonably reproduce ab initio molecular electrostatic potential (MEP), which guarantees their successful use in molecular modelling. To validate the approaches, the parameters of the proposed charge schemes were fitted to best reproduce MEP simultaneously on grids around a set of 227 diverse organic compounds. The residual errors in MEP reproduction due to calculated atomic charges were compared to those due to charges from known charge schemes.     

从分子中正电荷分数探讨常用溶剂的极性顺序

基于桑德逊电负性均衡原理,改进了计算方法,计算出溶剂分子中的正电荷分数,得到的常用溶剂极性顺序与实测顺序基本一致。改进的计算方法比受溶剂纯度等条件影响的实际测量更通用,并有一定的预见性。