Pointing the way to the products? Comparison of the stress tensor and the second-derivative tensor of the electron density

The eigenvectors of the electronic stress tensor can be used to identify where new bond paths form in a chemical reaction. In cases where the eigenvectors of the stress tensor are not available, the gradient-expansion-approximation suggests using the eigenvalues of the second derivative tensor of the electron density instead; this approximation can be made quantitatively accurate by scaling and shifting the second-derivative tensor, but it has a weaker physical basis and less predictive power for chemical reactivity than the stress tensor. These tools provide an extension of the quantum theory of atoms and molecules from the characterization of molecular electronic structure to the prediction of chemical reactivity.     

Is the ion-linear quadrupole capture rate constant anisotropic with respect to the sign of the product of the charge on the ion and the quadrupole moment of the molecule?

The sign of the charge-quadrupole moment product is shown to affect the rate of ion-linear quadrupole capture.

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Is the dynamical polarization a significant part of the contribution of the triples to the correlation energy?

One may call dynamical polarization of doubly excited configurations the energy lowering of these configurations under the response of the other electrons to the so-created fluctuation of the electric field. This contribution of triply excited configurations may be identified and calculated through a computation that only requires a computation time proportional to the sixth power of the number of molecular orbitals (MOs), instead of the seventh power for the total contribution of the triples. Its amplitude depends on the choice of the MOs and becomes important when localized MOs are used.     

Does the Temperature of the prise de mousse Affect the Effervescence and the Foam of Sparkling Wines?

The persistence of effervescence and foam collar during a Champagne or sparkling wine tasting constitute one, among others, specific consumer preference for these products. Many different factors related to the product or to the tasting conditions might influence their behavior in the glass. However, the underlying factor behind the fizziness of these wines involves a second in-bottle alcoholic fermentation, also well known as the prise de mousse. The aim of this study was to assess whether a low temperature (13 °C) or a high temperature (20 °C) during the in-bottle fermentation might have an impact on the effervescence and the foaming properties (i.e., collar height and bubble size) of three French sparkling wines (a Crémant de Loire and two Champagne wines), under standard tasting conditions. Our results showed that sparkling wines elaborated at 13 °C and served in standard tasting conditions (i.e., 100 mL, 18 °C) had better ability to keep the dissolved CO₂ (between 0.09 and 0.30 g/L) in the liquid phase than those elaborated at 20 °C (with P < 0.05). Most interestingly, we also observed, for the Crémant de Loire and for one Champagne wine, that the lower the temperature of the prise de mousse, the smaller (with P < 0.05) the bubbles in the foam collar throughout the wine tasting.     

Correlation Analysis of the Runoff of the Rivers and the Seisms in China

In recent hundred years the annual discharge variations of the Changjiang River (represented by the Yichang station) and the Huanghe River (represented by Shanxian and Tangnaihe, respectively) have closely related to the geographical distribution of the earthquakes coming about in China in the same year, Both the occurrence of the destructive seism or seismic swarm in the river basins and the disappearance of the shocks in the east and south of the basins are the conditions that the Changjiang and Huanghe Rivers are the high flow while that the strong earthquake of magnitude 7 or more occurred in North China is the condition for the Changjiang low flow year and that of 6 or more in the Qilian Mountains area is for the Huanghe River. In the latter part of this paper, a 2-year sample is given to explain that the conditions of the 2 rivers being high flow years are that the north-south seismic belt is active and in the meanwhile no seism occurred in South China, and those of the low flow year are that the     

Self-sorting: the exception or the rule?

In this paper, we pose the question of whether self-sorting in designed systems is exceptional behavior or whether it is likely to become a more general phenomenon governing molecular recognition and self-assembly. To address this question we prepared a mixture comprising two of Davis' self-assembled ionophores, Rebek's tennis ball and calixarene tetraurea capsule, Meijer's ureidopyrimidinone, Reinhoudt's calixarene bis(rosette), and two molecular clips in CDCl(3) solution and observed the behavior of this ensemble by (1)H NMR. As hypothesized, high-fidelity self-sorting behavior was observed. The influence of several key variables-temperature, concentration, equilibrium constants, and the presence of competitors-on the fidelity of self-sorting is described. These results show that self-sorting is neither the exception nor the rule. They suggest, however, that the subset of known molecular aggregates that exceed the criteria required for thermodynamic self-sorting is larger than previously appreciated and potentially quite broad.     

Micellar Copolymerization: the State of the Arts

Over the past two decades, hydrophobically modified water-soluble polymers (HMWSPs), particularly hydrophobically associating polyacrylamides (HAPAMs), have attracted increased interest owing to their practical and fundamental importance[1]. This system usually consists of a hydrophilic backbone with a small proportion (generally less than 2 mol %) of hydrophobic pendent groups. When dissolved in aqueous solutions, the apolar moieties tend to exclude water and are held together by intra- a…     

Noninvasive Detection of the Gases Inside the Sealed Batteries by the On-line Mass Spectrometry

Mass spectrometer is connected through an adaptor to a sealed small battery to probe the gas phase changes inside the battery. The factors influencing the response time are analyzed with a simplified model. The feasibility of the new technique is demonstrated with a Ni-Cd battery, showing different profiles of MS intensities for O2 and H2. Compared with gas chromatography, this technique has the advantage of being noninvasive and should be useful for the study and diagnostic examination of small sealed batteries.     

Exploration on the Biotechnological Aspect of the Ureolytic Bacteria for the Production of the Cementitious Materials—a Review

Biomineralization is a process that leads to the formation of minerals using the biologically or biotechnologically mediated route. Calcium carbonate is one such biomineral that is secreted by the ureolytic bacteria which contributes for the strengthening and improvement of cementitious and sandy materials. It is a new and innovative area in the geotechnological engineering and structural engineering due to its wide range of implications in strengthening of soil, sand, stone, and cementitious materials. The shape and size of the calcium carbonate particle vary with the strain of the bacterium used, and it is species specific. This paper aims in the critical review of the mechanism of calcium carbonate precipitation by the bacterium, various bacteria involved, and the useful outputs of the technique of biomineralization. Based on the critical review, it also recommends the future development and research in the field to develop a technology that can strengthen the existing and the proposed structures.     

Innenrücktitelbild: Developing Conjugated Polymers with High Electron Affinity by Replacing a C?C Unit with a B←N Unit (Angew. Chem. 12/2015)

The key parameters of conjugated polymers are lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels. Few approaches can simultaneously lower LUMO and HOMO energy levels of conjugated polymers to a large extent (>0.5 eV). Disclosed herein is a novel strategy to decrease both LUMO and HOMO energy levels of conjugated polymers by about 0.6 eV through replacement of a C C unit by a B←N unit. The replacement makes the resulting polymer transform from an electron donor into an electron acceptor, and is proven by fluorescence quenching experiments and the photovoltaic response. This work not only provides an effective approach to tune the LUMO/HOMO energy levels of conjugated polymers, but also uses organic boron chemistry as a new toolbox to develop conjugated polymers with high electron affinity for polymer optoelectronic devices.     

Developing Conjugated Polymers with High Electron Affinity by Replacing a CC Unit with a B←N Unit

The key parameters of conjugated polymers are lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels. Few approaches can simultaneously lower LUMO and HOMO energy levels of conjugated polymers to a large extent (>0.5 eV). Disclosed herein is a novel strategy to decrease both LUMO and HOMO energy levels of conjugated polymers by about 0.6 eV through replacement of a C? C unit by a B←N unit. The replacement makes the resulting polymer transform from an electron donor into an electron acceptor, and is proven by fluorescence quenching experiments and the photovoltaic response. This work not only provides an effective approach to tune the LUMO/HOMO energy levels of conjugated polymers, but also uses organic boron chemistry as a new toolbox to develop conjugated polymers with high electron affinity for polymer optoelectronic devices.     

基于芘并咪唑的电致发光材料的合成与表征

以芘和咪唑为基本构筑单元,利用"一锅法"合成了一系列芘并咪唑衍生物PyPI,PyTPAI,PyCzI和Pyd-CzI.采用质谱、核磁和元素分析等手段表征了化合物的结构.通过调节与芘并咪唑相连接的共轭基团的种类、大小和空间构型,实现对分子热学性质,分子轨道能级和光电性质的调控.进一步制备了有机电致发光器件,得到了较好的器件性能.     

Comparative study of Li, Na, and K adsorptions on graphite by using ab initio method

A comprehensive study has been conducted to compare the adsorptions of alkali metals (including Li, Na, and K) on the basal plane of graphite by using molecular orbital theory calculations. All three metal atoms prefer to be adsorbed on the "middle hollow site" above a hexagonal aromatic ring. A novel phenomenon was observed, that is, Na, instead of Li or K, is the weakest among the three types of metal atoms in adsorption. The reason is that the SOMO (single occupied molecular orbital) of the Na atom is exactly at the middle point between the HOMO and the LUMO of the graphite layer in energy level. As a result, the SOMO of Na cannot form a stable interaction with either the HOMO or the LUMO of the graphite. On the other hand, the SOMO of Li and K can form a relatively stable interaction with either the HOMO or the LUMO of graphite. Why Li has a relatively stronger adsorption than K on graphite has also been interpreted on the basis of their molecular-orbital energy levels.     

Structural, electronic, and optical properties of 9-heterofluorenes: a quantum chemical study

Density-functional theory studies were applied to investigate the structural, electronic, and optical properties of 9-heterofluorenes achieved by substituting the carbon at 9 position of fluorene with silicon, germanium, nitrogen, phosphor, oxygen, sulfur, selenium, or boron. These heterofluorenes and their oligomers up to pentamers are highly aromatic and electrooptically active. The alkyl and aryl substituents of the heteroatom have limited influence, but the oxidation of the atom has significant influence on their molecular structures and properties. The highest occupied molecular orbital (HOMO)-lowest occupied molecular orbital (LUMO) interaction theory was successfully applied to analyze the energy levels and the frontier wave functions of these heterofluorenes. Most heterofluorenes belong to type B of interaction with low-lying LUMO and have the second kind of wave function. Carbazole and selenafluorene have type C of interaction with high-lying HOMO and the third kind of wave function. Types C and D of heterofluorenes, such as carbazole, oxygafluorene, sulfurafluorene, and selenafluorene also have high triplet state energies. The extrapolated HOMO and LUMO for polyheterofluorenes indicate that polyselenonafluorene has the lowest LUMO; polycarbazole has the highest HOMO; polyselenafluorene has the highest bandgap (E(g)); and polyborafluorene has the lowest E(g). Heterofluorenes and their oligomers and polymers are of great experimental interests, especially those having extraordinary properties revealed in this study.     

Tuning of the electronic properties of H‐passivated armchair graphene nanoribbons by mild border oxidation: Theoretical study on periodic models

We report the results of a DFT study of the electronic properties, intended as highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies, of periodic models of H‐passivated armchair graphene nanoribbons (a‐GNRs) as that synthetized by bottom‐up technique, functionalized by vicinal dialdehydic groups. This material can be obtained by border oxidation in mild and easy to control conditions with ¹Δ_g O₂ as we reported in our previous paper (Ghigo et al., ChemPhysChem 2015, 16, 3030). The calculations show that the two models of border oxidized a‐GNRs (model A, 0.98 nm and model B, 1.35 nm wide) present LUMO and HOMO energies lowered by an extend roughly linearly dependent on the amount of oxygen chemically bound. The frontier orbital energy variations dependence on the % wt of oxygen bound are, for model A: ?0.12 eV for the LUMO and ?0.05 eV for the HOMO; for model B: ?0.15 eV (HOMO) and ?0.06 eV (LUMO). © 2016 Wiley Periodicals, Inc.     

氟硼二吡咯类pH荧光探针PET光谱特性的理论计算

氟硼二吡咯(BODIPY)类pH荧光探针分子是基于光诱导电子转移(PET)的荧光探针分子, 识别基团氮原子上引入不同取代基可呈现不同的光学灵敏度. 本文应用密度泛函理论(DFT)及含时密度泛函理论(TD-DFT)方法对六种含不同取代基的探针分子进行了几何构型优化及激发态计算, 探讨了不同取代基对PET效应影响. 计算结果表明: 基态时这些探针分子的最高占有分子轨道(HOMO)和最低未占有分子轨道(LUMO)都在荧光母体BODIPY的π, π^*轨道, 而识别基团上氮原子孤对电子所在的轨道为HOMO-1轨道. 但是在激发态, 当氮原子上有两个取代基时, HOMO-1→LUMO跃迁的激发能都小于荧光团的HOMO→LUMO跃迁, 这将有可能产生PET效应并导致荧光熄灭, 而当氮原子上有一个取代基时不会出现这种现象. 通过激发态结构优化可以发现, 无论识别基团氮原子上有一个还是两个取代基, N原子的轨道对称性都发生变化, 由sp³→sp², 孤对电子占据在p轨道上, 其轨道能级升高至荧光团的HOMO和LUMO轨道之间, 将导致不同程度的PET效应, 与实验结果一致.     

Rhodanine flanked indacenodithiophene as non-fullerene acceptor for efficient polymer solar cells

A fused-ring electron acceptor IDT-2BR1 based on indacenodithiophene core with hexyl side-chains flanked by benzothiadiazole rhodanine was designed and synthesized.In comparison with its counterpart with hexylphenyl side-chains(IDT-2BR),IDT-2BR1exhibits higher highest occupied molecular orbital(HOMO)energy but similar lowest unoccupied molecular orbital(LUMO)energy(IDT-2BR1:HOMO=-5.37eV,LUMO=-3.67eV;IDT-2BR:HOMO=-5.52eV,LUMO=-3.69eV),red-shifted absorption and narrower bandgap.IDT-2BR1 has higher electron mobility(2.2×10~(-3)cm~2 V~(-1)s~(-1))than IDT-2BR(3.4×10~(-4)cm~2 V~(-1)s~(-1))due to the reduced steric hindrance and ordered molecular packing.Fullerene-free organic solar cells based on PTB7-Th:IDT-2BRl yield power conversion efficiencies up to 8.7%,higher than that of PTB7-Th:IDT-2BR(7.7%),with a high open circuit voltage of0.95 V and good device stability.     

有机半导体非平衡态HOMO和LUMO能量位移规律与OLED中“热激子”形成的唯象理解

以能斯特方程为基础, 通过分析电流密度与氧化还原物种活度变化, 即载流子浓度变化的关系, 计算出有机半导体材料电极电势的变化, 从而建立起有机半导体前线轨道, 即最高占据分子轨道(HOMO)能级和最低未被占据分子轨道(LUMO)能级相对于热力学平衡态的能量位移随电流密度变化的数学关系. 进而依据能级能量位移引起的能隙变化, 提出了有机电致发光显示器（OLED）中“热激子”的产生机制.     

Theoretical Studies on Structural and Spectroscopic Properties of Photoelectrochemical Cell Ruthenium Sensitizers-the Derivatives of N3

A series of dye molecules was designed theoretically. Particularly, azoles and their derivatives were chosen as the modifying groups linking to ancillary ligands of [Ru(dcbpyH₂)₂(NCS)₂](N3, dcbpy=4,4′-dicarboxy- 2,2′-bipyridine; NCS=thiocyanato). Density functional theory(DFT) based approaches were applied to exploring the electronic structures and properties of all these systems. The dye molecule with 1,2,4-triazole groups which exhibits a very high intensity of absorption in visible region, was obtained. Time-dependent DFT(TD-DFT) results indicate that the ancillary ligand dominates the molecular orbital(MO) energy levels and masters the absorption transition nature to a certain extent. The deprotonation of anchoring ligand not only affects the frontier MO energy levels but also controls the energy gaps of the highest occupied MO(HOMO) to the lowest unoccupied MO(LUMO) and LUMO to LUMO+1 orbital. If the gap between LUMO-LUMO+1 is small enough, the higher efficiency of dye-sensitized solar cell(DSSC) should be expected.