Structural Study on NMR and X-Ray of Lactucopicrin—A Guaianolide Ester

The guaianolide ester is a potent inhibitor of cancer cells. Lactucopicrin, a guaianolide, shows analgesic, antitussic, and sedative activities. In order to investigate its structure, ¹H and ¹³C NMR and 2D NMR have been carried out at a proton field strength of 400 MHz and a carbon field strength of 100 Mhz in DMSO-d ₆ at 20°C. Resonances for all protons and carbons have been assigned. The results of HMQC and HMBC experiments suggest that the structure of lactucopicrin is as shown in Fig. 1. Its stereostructure is verified by the X-ray experiment. ¹H and ¹³C NMR of lactucopicrin are reported. Its 2D NMR and X-ray are reported for the first time.     

Study of the winter and summer changes of the air composition in the church of Szalowa, Poland, related to conservation

The St. Michael Archangel’s Church in Szalowa, Poland, was selected for closer investigation with respect to the indoor/outdoor air exchange and its influence on the air quality and work arts preservation. Chemical composition, size and abundance of particulate matter and concentration of gases NO₂, SO₂, O₃ inside and outside the church were determined. To study seasonal variation of the weather condition (temperature, inversion level, wind direction) and the influence of seasonal sources of the air pollution (like heating of the nearby houses), samples were collected in winter and summer time. It was stated that suspended particulate matter inside the wooden church has in general an outdoor source. Several groups of particles were distinguished such as the organic ones, soil dust, nitrates and sulphates. In case of organic and soil dust particles, the concentration inside was higher than outside. From the results, in comparison to literature data, one can conclude that accumulation of particulate suspended matter in the church is more intense than in other types of buildings. Gaseous pollutants were detected but their concentration was negligible.     

Modification of the halogen end groups of polystyrene prepared by ATRP

The stabilization modification of the halogen end groups of polystyrene prepared by atom transfer radical polymerization (ATRP) has been attempted. The reaction mechanism adopted is radical chain transfer reaction, and iso-propylbenzene is employed as not only the chain transfer agent but also the solvent. Moreover, Cu⁰ is used as the acceptor of the transformed halogen atom in some experiments. As evidenced by ¹H NMR analysis of the modified products, the halogen end group can really be converted into the much more stable carbon-hydrogen structure. When Cu⁰ is not used, the conversion of the halogen end groups rises rapidly during the early stage and the increase rate slows down after about 8 h reaction. In view of the influence of reaction temperature on the modification, the conversion increases almost exponentially with temperature in the range of 80-100 °C, and the increase rate slows down at higher temperature. ¹H NMR and SEC analyses prove that the modification reaction does not destroy the polymer backbone and the molecular weights remain almost the same as those of the unmodified samples. When Cu⁰ is introduced, the modification reaction proceeds much rapidly, the conversion of the halogen end groups rises almost linearly at the early stage and the nearly complete (>95%) dehalogenation of the polymeric chains is observed after only 12 h reaction. However, the molecular weights rise and the polydispersities become wider after the modification, which implies that the modification is accompanied with the couple termination of the polystyrene radicals besides chain transfer reaction. Furthermore, the couple termination can be restrained at some lower catalyst concentration. Indeed, the modified polymers show improved thermal stability, the initial weight loss temperatures is increased from 196 °C to 378 °C for the linear polystyrene and from 203 °C to 261 °C for the hyperbranched polystyrene.     

Hydrogenated polybutadiene–polymethyl methacrylate (HPB–PMMA) block copolymer. I. Synthesis of polybutadiene–polymethyl methacrylate (PB–PMMA) block copolymer

To get hydrogenated polybutadiene-polymethyl methacrylate (HPB-b-PMMA) block copolymer to be used as a compatibilizer for blends of polyolefin/polar polymer, PB-b-PMMA was synthesized by anionic-free radical mechanism transformation polymerization. Selective extraction, gradient elution thin layer chromatography, and oil-oil emulsion separation techniques were tried to attempt to separate the copolymerization products. Hydrogenation of the PB sequence in PB-b-PMMA yielded HPB-b-PMMA. The compatibilizing function of PB-b-PMMA was shown in blending experiments. © 1993 John Wiley & Sons, Inc.     

The Direct Resolution of the Enantiomers of Four Chiral Pesticides

Cellulose-tris(3,5-dimethylphenylcarbamate)(CDMPC) were synthesized as highperformance liquid chromatography (HPLC) chiral stationary phase(CSP). The successful resolution of four chiral pesticides on the CSP was realized and the influence of the temperature on the separation was studied.     

Phase behavior and interfacial properties of nonadditive mixtures of Onsager rods

Within a second virial theory, we study bulk phase diagrams as well as the free planar isotropic-nematic interface of binary mixtures of nonadditive thin and thick hard rods. For species of the same type, the excluded volume is determined only by the dimensions of the particles, whereas for dissimilar ones it is taken to be larger or smaller than that, giving rise to a nonadditivity that can be positive or negative. We argue that such a nonadditivity can result from modeling of soft interactions as effective hard-core interactions. The nonadditivity enhances or reduces the fractionation at isotropic-nematic (IN) coexistence and may induce or suppress a demixing of the high-density nematic phase into two nematic phases of different composition (N(1) and N(2)), depending on whether the nonadditivity is positive or negative. The interfacial tension between coexisting isotropic and nematic phases shows an increase with increasing fractionation at the IN interface, and complete wetting of the IN(2) interface by the N(1) phase upon approach of the triple-point coexistence. In all explored cases bulk and interfacial properties of the nonadditive mixtures exhibit a striking and quite unexpected similarity with the properties of additive mixtures of different diameter ratio.     

Fractal phenomena in molecular mechanics calculation

It is proposed that in molecular mechanics calculation points belonging to various stable or meta-sta-ble conformtrs are mixed up and form fractal structures in conformation space.The calculation results show the following two phenomena:(i)Two levels of structure with fractal feature were observed.Around the conformer without mirror symmetry points belonging to the conformer and its enantiomer are mixed up and form the first level of fractal structure; on the boundary of the attractive basin o{ each atlractor,points belonging to different attractors form the second level of fractal structure.(ii) The variation of molecular mechanics parameters will influence the structure and area of each attractive basin significantly The above phenomena may become the basis of a new method for solving the troublesome multi-minimum-point problem in molecular mechanics calculation.     

全硅MCM-41担载的加氢脱硫催化剂的TPR研究

用TRP技术研究了以全硅MCM-41(Si-MCM-41)和HNO3交换的全硅MCM-41(H-MCM-41)为载体制备的Ni-Mo、Co-Mo和Ni-W加氢脱硫(HDS)催化剂的还原性能，并以0．8(wt)％二苯并噻吩(DBT)的十氢萘溶液为模型化合物，在高压固定床反应器上考察了上述催化剂的加氢脱硫(HDS)反应性能。结果表明，Si-MCM-41经稀HNO3交换后，所担载的Ni-Mo和Ni-W催化剂还原性能、HDS活性和加氢活性有显著变化，但对Co-Mo催化剂影响不大。这说明在Ni-Mo／H-MCM-41和Ni-W／H-MCM-41中可能存在氢溢流现象，DBT的HDS活性与载体表面酸性和氢溢流有关。     

重要生物微量元素和常见负电性元素在不同价态和电子组态下的轨道指数和电负性

本文用Xα方法计算出不同价态与电子组态下锰、铁、钴、铜、锌及钼等过渡族重要生物微量元素和氮、氧、氟、磷、硫、氯、硒和溴等常见负电性元素的数值原子轨道和轨道电负性值,再用数值拟合方法得出这些原子轨道的单ξ和双ξSlater型基函数的指数.研究了这些元素的原子所带电荷和电子组态对其原子轨道指数与轨道电负性的影响,给出了相应的回归公式.这些公式有较高的精确度,不但为研究这些元素化合物的电子结构提供基础参数,也为电荷自洽型的计算提供较可靠的计算公式.     

Lanthanide MOFs for inducing molecular chirality of achiral stilbazolium with strong circularly polarized luminescence and efficient energy transfer for color tuning

We present herein an innovative host–guest method to achieve induced molecular chirality from an achiral stilbazolium dye (DSM). The host–guest system is exquisitely designed by encapsulating the dye molecule in the molecule-sized chiral channel of homochiral lanthanide metal–organic frameworks (P-(+)/M-(−)-TbBTC), in which the P- or M-configuration of the dye is unidirectionally generated via a spatial confinement effect of the MOF and solidified by the dangling water molecules in the channel. Induced chirality of DSM is characterized by solid-state circularly polarized luminescence (CPL) and micro-area polarized emission of DSM@TbTBC, both excited with 514 nm light. A luminescence dissymmetry factor of 10⁻³ is obtained and the photoluminescence quantum yield (PLQY) of the encapsulated DSM in DSM@TbTBC is ∼10%, which is close to the PLQY value of DSM in dilute dichloromethane. Color-tuning from green to red is achieved, owing to efficient energy transfer (up to 56%) from Ln³⁺ to the dye. Therefore, this study for the first time exhibits an elegant host–guest system that shows induced strong CPL emission and enables efficient energy transfer from the host chiral Ln-MOF to the achiral guest DSM with the emission color tuned from green to red.

Homochiral Ln-MOFs are synthesized to encapsulate achiral dyes to induce strong circularly polarized luminescence with a luminescence dissymmetry factor of 10⁻³.