Synthesis and spectroscopic properties of highly water-soluble perylene derivatives

Most known perylene diimides are lipophilic, with few exceptions of hydrophilic derivatives. Even in the latter case, the compounds have limited water solubility and show a strong tendency to self-aggregation. In this paper we present the synthesis of four new perylene derivatives with three and four basic side chains, obtained by functionalizing the bay-area of perylene. These molecules show great solubility in aqueous media as hydrochlorides and their tendency to self-aggregate is remarkably reduced with respect to the previously synthesized two-chained perylene diimides. Their different spectroscopic properties in various solvents and conditions are reported and discussed.     

气相分子吸收光谱法测定地下水中亚硝酸盐氮、氨氮、硝酸盐氮

采用气相分子吸收光谱法测定地下水中的亚硝酸盐氮(NO2^-)、氨氮(NH4^+)、硝酸盐氮(NO3^-)。考察NO2^-,NH4^+和NO3^-测定时的相互干扰,并给出了相应的消除方法。研究结果表明,测定NO2^-时,NH4^+和NO3^-无干扰;NO2^-对测定NH4^+和NO3^-产生干扰,可分别采用分段法和加入2滴10%氨基磺酸溶液的方法消除干扰;对于不含NO2^-或NO2-含量不高的地下水样品,可简化操作步骤直接测定NO3^-。该方法测定结果的相对标准偏差为0.73%~2.74%(n=12),样品加标回收率为97.67%~100.28%。所用检测仪器具有流动注射、自动进样及在线绘制标准曲线的功能,简化了标准方法中的样品前处理过程,减少了样品的损失,实现了自动化分析,大幅提高了检测结果的准确度和工作效率。     

Study of the α-relaxation of PVC, EVA and 50/50 EVA70/PVC blend

The dipole dynamics and α-relaxation behaviour of polyvinyl chloride PVC, poly(ethylene-co-vinyl-acetate) EVA₇₀ and blend of them EVA₇₀/PVC have been investigated by differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). The differential scanning calorimetry (DSC) thermograms measured on samples show a single glass transition in the analysed temperature range. These three polymers are wholly amorphous and pure PVC and pure EVA₇₀ are miscible in the ratio 1:1. The glass transition temperature T_g decreases significantly with presence of EVA₇₀. Furthermore, the values of apparent activation energies for molecular motions at the α-relaxation and the values of fragility index have also been determined for each sample using Moynihan expression for DSC results and Vogel-Fulcher-Tammann-Hesse (VFTH) form for DRS results. It is shown a large dependence of all the values of these parameters with the content of EVA₇₀. Comparing these three polymers, we found that the more fragile glass forming liquid is the PVC. Fragility decreases drastically with EVA₇₀ content. EVA₇₀ and EVA₇₀/PVC blend exhibit practically the same behaviour. The effect of inter- and intra-molecular interactions on fragility is discussed to explain these variations.     

Mechanistic approaches to asymmetric synthesis of aziridines from guanidinium ylides and aryl aldehydes

To approach more realistic mechanisms for asymmetric aziridine synthesis from guanidinium ylides and aryl aldehydes, reactions were systematically carried out by using a variety of p-substituted benzaldehydes under modified conditions. Two kinds of reaction mechanisms controlled by the nature of the p-substituents of aryl aldehydes is proposed for the two-steps aziridine synthesis composed of a C-C bond formation by nucleophilic addition of guanidinium ylides to aryl aldehydes (step 1) and the fragmentation of intermediate adducts to aziridine products by intramolecular nucleophilic substitution (step 2). A S_Ni-like mechanism via cationic-like transition state is proposed for step 2 in the asymmetric synthesis using EDG-substituted benzaldehydes, whereas with EWG-substituted benzaldehydes, a S_N2-like mechanism is proposed. Hammett analysis, based on the diastereomeric ratio in the aziridine products, is consistent with the proposed rate-determining steps in these two mechanisms. A second Hammett analysis, based on the enantiomeric ratio of the aziridine products, clearly reveals the difference in the susceptibilities to the electronic substituents effect between step 1 and step 2.     

ToF‐SIMS studies of the oxidation of Fe by D2O vapour: comparison with XPS

The oxidation of iron (Fe) by water (D₂O) vapour at low pressures and room temperature was investigated using time‐of‐flight (ToF) SIMS. The results supported those found previously using XPS and the QUASES^? program in that a duplex oxide structure was found containing a thin outer surface hydroxide (Fe(OD)₂) layer over an inner oxide (FeO) layer. The extraordinary depth resolution of the ToF‐SIMS profiles assisted in identifying the two phases; this resolution was achieved by compensation for surface roughness. A substantial concentration of deuterium was found in the subsurface oxide layer. This observation confirmed previous assessments that the formation of FeO was from the reaction of Fe(OD)₂ with outward‐diffusing Fe, leaving deuterium as a reaction product. Copyright © 2005 John Wiley & Sons, Ltd.     

A new strategy for the synthesis of α,β-diaroylpropionates promoted by samarium metal in DMF

When promoted by samarium in DMF, aroyl chlorides react readily with acrylates to afford α,β-diaroylpropionates in good to excellent yields without pretreating or activating the metallic samarium.     

Solution- and bound-state conformational study of N,N',N"-triacetyl chitotriose and other analogous potential inhibitors of hevamine: application of trNOESY and STD NMR spectroscopy

The solution-state conformations of N,N',N"-triacetyl chitotriose (1) and other potential chitinase inhibitors 2-4 were studied using a combination of NMR spectroscopy (NOESY) and molecular mechanics calculations. Determination solely of the global energy minimum conformation was found to be insufficient for an agreement with the NMR results. An appropriate consistency between the NMR experimental data and theoretical calculations was only reached by assessing the structures as population-weighted average conformers based on Boltzmann distributions derived from the calculated relative energies. Analogies, but also particular differences, between the synthetic compounds 2-4 and the naturally-occurring N,N',N"-triacetyl chitotriose were found. Furthermore, the conformation of compounds 1 and 2 when bound to hevamine was also studied using transferred NOESY experiments and the binding process was found to impart a level of conformational restriction on the ligands. The preferred conformation as determined for 1 in the bound state to hevamine belonged to one of the conformational families found for the compound when free in solution, although full characterisation of the bound-state conformations was impeded due to severe signal overlap. Saturation transfer difference NMR experiments were also employed to analyse the binding epitopes of the bound compounds. We thus determined that it is mainly the acetyl amido groups of the trisaccharide and the heterocyclic moiety which are in close contact with hevamine.     

Co‐Conformational Distribution of Nanosized [2]Catenanes Determined by Pulse EPR Measurements

The co‐conformational ensembles of three differently sized [2]catenanes were studied by measuring pair correlation functions corresponding to the separation of nitroxide spin labels—one attached to each of the two macrocycles—with the double electron–electron resonance (DEER) experiment. A geometric model for the [2]catenanes was derived that approximates the macrocycles by circles and takes into account the topological constraint. Comparison of the experimental to the theoretically predicted pair correlation functions gives insight into the co‐conformational distribution and the size of the macrocycles. It was found that the macrocycles of the medium‐ and large‐sized catenanes in chloroform are close to fully expanded, while they are partially collapsed in glassy o‐terphenyl. For the small‐sized catenane, moderate interaction between the unsaturated sections of the macrocycles in chloroform is indicated by a slight overrepresentation of short label‐to‐label separations in the pair correlation function.     

Density and Speed of Sound for Binary Mixtures of a Cyclic Ether with a Butanol Isomer

Densities and speeds of sound of the binary mixtures 1,3-dioxolane + 1-butanol, 1,3-dioxolane + 2-butanol, 1,4-dioxane + 1-butanol, and 1,4-dioxane + 2-butanol have been measured at 25 and 40°C. The excess molar volumes and excess isentropic compressibility coefficients were calculated from experimental data and fitted to a Redlich–Kister polynomial function. Results were analyzed in terms of molecular interactions and compared with literature data.     

Ein neues Kupfercobaltboratoxid mit isolierten B2O5-Baugruppen: Cu2Co(B2O5)O

On a New Copper Cobalt Borate Oxide with Isolated B₂O₅ Units: Cu₂Co(B₂O₅)O Single crystals of a new compound with the empirical formula Cu₂CoB₂O₆ were obtained by using a B₂O₃ flux technique. X-ray single crystal technique led to a new structure type. Cu₂CoB₂O₆ crystallizes monoclinic, space group C-P2₁/c (No. 14); a = 3.2250(6); b = 14.847(1); c = 9.1171(6) Å; β = 93.67°; Z = 4. All metal sites are octahedrally coordinated and form a two dimensional framework consisting of edge sharing octahedra ribbons. In addition one observes isolated B₂O₅-units and oxygen which is not coordinated to boron. The far relation to the crystal structure of the mineral Warwickite is illustrated.