Phanes with Three- and Four-Membered Rings as Building Elements

The systematic integration of the small 2π- and 4π-electron systems cyclopropenylium ion, cyclopropenone, oxo-cyclobutenylium ion, and cyclobutadiene into phane chemistry was initiated only a few years ago. [n₂]Cyclopropenylophanes, [n₂]cyclopropenonophanes, metal-capped [n₄]cyclobutadienosuperphanes, and other new families of double-decker phane species became available from cycloalkydiynes through special methods of double [2+1]cycloaddition with carbenes and metal complex induced dimerization by double [2+2]cycloaddition. Phane-specific structural features were elucidated by X-ray structural analyses. Cyclic voltammetry and PE spectroscopy as well as MO calculations reealed considerable interactions between closely spaced π-electron systems. Decapping cyclobutadienosuperphanes formally extended the synthetic principle to threefold [2+2]cycloadditions resulting in [n₄]-bridged tricyclo-[4.2.0.0^{3, 5}]octa-3,7-dienes, which represent a new type of cage compounds. Moreover, completion to fourfold [2+2]addition was achieved with the photoinduced transformation of [3₄]bridged tricyclo[4.2.0.0^{3, 5}]octa-3,7-diene into propella[3₄]cubane.     

Interactions of dicarboxylic porphyrins with membranes in relation to their ionization state

The interactions of dicarboxylic porphyrins with membrane systems are discussed with particular emphasis on the effect of the charge of the porphyrin and the nature of the side-chains. The incorporation of hematoporphyrin or related dicarboxylic porphyrins within small unilamellar vesicles as membrane models is favored by a decrease of the pH in the range of physiological pH values. This effect might play an important role in the retention of porphyrins by tumors, which are more acidic than normal tissues. Kinetics studies also show that the partition of the porphyrin between the lipidic bilayer and the aqueous phase is governed by its release rate rather than by its incorporation rate.     

DIFFUSION OF LONG CHAINS THROUGH A POROUS THIN GEL NETWORK

Using a core(142 nm)made of linear polystyrene(PS)chains as a seed,we further polymerized a thin layer of cross-linked PS shell(7 nm)on it in water to form a core-shell particle.Such a particle swells in toluene,which enables linear PS chains inside the core to gradually diffuse out through the porous shell.Using a combination of static and dynamic laser light scattering,we examined the chain diffusion process by following the change of the scattering intensity(i.e.the average molar mass of the particles).For the first time,we have revealed that the diffusion exhibits three stages.In the first stage,the chain diffusion through the shell is even faster than their translational diffusion in a dilute solution.The three stages respectively correspond to the change of the solution in the core from concentrated to semidilute and then from semidilute to dilute.     

High speed liquid chromatography with small bore columns

Using a specially designed column system, we have systematically investigated the effect of mobile phase velocity on column efficiency. The performance of small bore columns operated at different linear velocities of mobile phase was examined for three different types of injection system. Using the value of H^∞/u or n^∞/t${}_{\text{r}}^{\text{º}}$ as a criterion of a high speed separation, we calculated values of n/t${}_{\text{r}}^{\text{º}}$ for different solutes according to the equation \documentclass{article}\pagestyle{empty}\begin{document}$ {{\rm n}\mathord{\left/ {\vphantom {{\rm n} {{\rm t}_{\rm r}^ \circ }}}\right. \kern-\nulldelimiterspace} {{\rm t}_{\rm r}^ \circ }} = {{{\rm n}^\infty } \mathord{\left/ {\vphantom {{{\rm n}^\infty } {{\rm t}_{\rm r}^ \circ }}} \right. \kern-\nulldelimiterspace} {{\rm t}_{\rm r}^ \circ }}\left({\frac{{1 + {\rm k'}}}{{{\rm k' + }\beta }}} \right)^2 $\end{document}; the results obtained are in agreement with the experimentally determined values. These systematic investigations culminated in the separation of seven compounds in less than 10 s; the respective chromatogram is shown.     

Investigations of the local distortions and EPR parameters for Cu2+ in xNa2O‐(30–x)K2O‐70B2O3 (5 ≤ x ≤ 25 mol%) glasses

The local distortions and electron paramagnetic resonance parameters for Cu²⁺ in the mixed alkali borate glasses xNa₂O‐(30–x)K₂O‐70B₂O₃ (5 ≤ x ≤ 25 mol%) are theoretically studied with distinct modifier Na₂O compositions x. Owing to the Jahn–Teller effect, the octahedral [CuO₆]¹⁰⁻ clusters show significant tetragonal elongation ratios p ~19% along the C₄ axis. With the increase of composition x, the cubic field parameter Dq and the orbital reduction factor k exhibit linearly and quasi‐linearly decreasing tendencies, respectively, whereas the relative tetragonal elongation ratio p has quasi‐linearly increasing rule with some fluctuations, leading to the minima of g factors at x = 10 mol%. The composition dependences of the optical spectra and the electron paramagnetic resonance parameters are suitably reproduced by the linear or quasi‐linear relationships of the relevant quantities (i.e., Dq, k, and p) with x. The above composition dependences are analyzed from mixed alkali effect, which brings forward the modifications of the local crystal‐fields and the electronic cloud distribution around Cu²⁺ with the variation of the composition of Na₂O.     

Radiation chemistry of tris(acetylacetonato) cobalt(iii) in aqueous solutions

Abstract

On radiolysis tris(acetylacetonato) cobalt(III) in aqueous solutions is found to get reduced by reaction with (1) hydrated electrons, (2) H atoms, (3) OH radicals and (4) C₂H₂OH radicals. The bimolecular rate constants for the first three reactions, determined by competition kinetics are: 4 × 10¹⁰, 2.3 × 10⁹ and 4.7 × 10⁹ M^?1sec^?1 respectively. Absorption spectra of the irradiated solutions indicate the formation of bis(acetylacetonato) cobalt(II) from reaction (1), but not from (3). The total cobaltous yield in air-free solutions is given byG(Co⁺⁺) = 5.6 and 6.5 at pH 6.5 and 1 respectively. It appears that G_eaq- ∽ _H ⁺ G_oH ∽ 2.8 in neutral solutions. Considerations of material balance for the primary yields of radiolysis of water suggest the possibility that the so-called independent H-atoms in neutral solutions are probably excited water molecules or ion-pairs.     

Defect-effects on the photoluminescence of ZrO2 bulk,film and nanocrystals

The photoluminescence (PL) properties of ZrO₂ have been measured at different temperatures between 7 and 300 K, using various kinds of ZrO₂ specimens: bulk crystal melt-grown by a large solar furnace, thermally oxidized zirconium plate (ZrO₂ film crystal on Zr ) and nanocrystals (surface area: 35–45m²/g, diameter: 20–30 nm). The results clarify the deep and shallow energy level structures in the energy gap. Reversible UV-laser-light-induced spectral changes are observed for all of the specimens in different specimen-atmospheres (vacuum and O₂ gas). The results elucidate the defect-effects of the PL properties and the PL enhancement mechanism in ZrO₂ nanocrystals.     

In vitro metabolism study of Strychnos alkaloids using high‐performance liquid chromatography combined with hybrid ion trap/time‐of‐flight mass spectrometry

In this report, the in vitro metabolism of Strychnos alkaloids was investigated using liquid chromatography/high‐resolution mass spectrometry for the first time. Strychnine and brucine were selected as model compounds to determine the universal biotransformations of the Strychnos alkaloids in rat liver microsomes. The incubation mixtures were separated by a bidentate‐C₁₈ column, and then analyzed by on‐line ion trap/time‐of‐flight mass spectrometry. With the assistance of mass defect filtering technique, full‐scan accurate mass datasets were processed for the discovery of the related metabolites. The structural elucidations of these metabolites were achieved by comparing the changes in accurate molecular masses, calculating chemical component using Formula Predictor software and defining sites of biotransformation based upon accurate MSⁿ spectral information. As a result, 31 metabolites were identified, of which 26 metabolites were reported for the first time. These biotransformations included hydroxylation, N‐oxidation, epoxidation, methylation, dehydrogenation, de‐methoxylation, O‐demethylation, as well as hydrolysis reactions. Copyright © 2013 John Wiley & Sons, Ltd.     

A novel design of membrane mirror with small deformation and imaging performance analysis in infrared system

A method of diminishing the shape error of membrane mirror is proposed in this paper. The inner inflating pressure is considerably decreased by adopting the pre-shaped membrane. Small deformation of the membrane mirror with greatly reduced shape error is sequentially achieved. Primarily a finite element model of the above pre-shaped membrane is built on the basis of its mechanical properties. Then accurate shape data under different pressures can be acquired by iteratively calculating the node displacements of the model. Shape data are applicable to build up deformed reflecting surfaces for the simulative analysis in ZEMAX. Finally, ground-based imaging experiments of 4-bar targets and nature scene are conducted. Experiment results indicate that the MTF of the infrared system can reach to 0.3 at a high spatial resolution of 10l p/mm, and texture details of the nature scene are well-presented. The method can provide theoretical basis and technical support for the applications in lightweight optical components with ultra-large apertures.     

含酮基团对煤焦异相还原NO的影响

基于量子化学密度泛函理论和过渡态理论研究了含酮基团对煤焦异相还原NO的影响及其产物发生氧脱附的微观反应机理。计算结果表明，NO更易于吸附在含酮基团煤焦表面。椅形含酮基团强化了煤焦异相还原NO；锯齿形含酮煤焦表面与NO异相反应决速步能垒值（495.45 kJ/mol）大于锯齿形纯碳基煤焦表面与NO决速步能垒值（331.32 kJ/mol），基于锯齿形含酮煤焦模型中的氧浓度不在利于NO还原的范围内而不易于NO的还原。中间产物P1在无CO存在情况下，较纯碳基煤焦表面更易于发生氧脱附而产生表面缺陷；在CO存在条件下，含酮煤焦表面为氧脱附过程提供自由活性位点，降低了过程能垒消耗。