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Joachim Angelkort Sander van Smaalen Prof. Dr. Sven Oliver Hauber Mark Niemeyer 《无机化学与普通化学杂志》2007,633(7):1031-1035
Single crystal X‐ray diffraction of Eu(SC36H49)2 has revealed a first order phase transition at a temperature of 119 K, that involves a reduction of the specific volume by 1 %. The transition corresponds to a doubling of the unit cell, as it is the result from reorientations of isopropyl groups that appear at peripheral sites of the organic ligands. It is argued that a denser packing is achieved at the expense of a less favourable conformation of one of the two crystallographically‐independent complexes in the low‐temperature phase. The Bond‐Valence method is used to show that interactions of equal strengths are present between europium and both sulphur atoms and both coordinating phenyl rings. 相似文献
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本文综合评述了近年来2-[2-(二环己膦基)苯基]-1-甲基-1H-吲哚(CM-Phos)膦配体及其衍生物在钯催化的交叉偶联反应中的应用, 主要根据不同种类的交叉偶联反应进行系统性分述, 并对该领域的发展前景进行了展望. 相似文献
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Differential scanning calorimetric analyses were conducted on samples of poly(vinylidene fluoride) polymerized in an autoclave by tributylborane-oxygen by free-radical initiation at low temperature (-70-0°C). The peak melting points and the percent head-to-head defect in each polymer sample were determined by a reported calorimetric method. A commercial sample showed a melting temperature in the range 157–162°C and a percent head-to-head defect of 7.7%; whereas two experimental samples showed melting temperatures in the range 172–179°C with a percent head-to-head defect of 4.4 and 4.9%. The calorimetric procedure was modified by reducing annealing times to only 2 h, which saves time and, as shown in this study, avoids thermal polymer degradation. 相似文献
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Summary This paper gives a survey of the meander model of condensed polymers in their amorphous state. In a first part the bundle model of nearly straight chains is shortly described together with its short range order which agrees with the experimental evidence. Next, superstructures composed of tightly folded bundles are shown to be thermodynamically stable mainly by virtue of the segment-lines interchange entropy. TheGibbs free energy, the geometry and the radius of gyration of meanderlike folded molecules are evaluated. They only depend on molecular parameters like the interchain distance, the length of a kink segment and the energy of a fold. All results are in agreement with experimental evidence including recent reports byPetermann andGleiter (51, 52).
Zusammenfassung Die Arbeit gibt einen Überblick über das Mäandermodell kondensierter Polymere im amorphen Zustand. In einem ersten Abschnitt wird das Bündelmodell aus nahezu gestreckten Ketten kurz beschrieben und seine Nahordnung mit experimentellen Aussagen verglichen. Danach wird gezeigt, daß Superstrukturen aus enggefalteten Kettenbündeln thermodynamisch stabil sind, wofür in erster Linie die Vertauschungsentropie der Segmentzeilen verantwortlich ist. Die Freie Enthalpie, die Geometrie und der Trägheitsradius mäanderförmig gefalteter Moleküle werden berechnet. Sie sind nur von molekularen Parametern wie Kettenabstand, Kinksegmentlänge und Faltenenergie bestimmt. Alle Resultate stehen in Übereinstimmung mit experimentellen Ergebnissen, einschließlich neuerer Befunde vonPetermann undGleiter (51, 52).相似文献
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Reaction of LnCl3 with KSeAr* in thf afforded the unsolvated, alkane-soluble complexes LnCl(SeAr*)2 (Ln = Nd, Pr; Ar* = 2,6-Trip(2)C(6)H(3); Trip = 2,4,6-iPr(3)C(6)H(2)) in which the rare-earth metal cations show additional eta6-pi-coordination by two flanking arene rings. 相似文献
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利用氧化钕和盐酸为原料制得Nd(phen)2Cl3(三氯二邻菲罗啉合钕),测得其光谱特性并以稀土氧化钕、苯甲酸和邻菲罗啉为原料制得绿色液体激光介质钕离子的配合物——NdB3phen(三苯甲酸—邻菲罗啉合钕).利用飞秒激光器,采用单光束Z-扫描法研究了NdB3phen的三阶非线性光学特性.结果表明:当入射飞秒激光脉冲波长为400 nm,峰值功率密度为2.94×1014 W/m2,脉宽为117 fs时,测得样品NdB3phen的非线性折射率为-2.84×10-18 cm2/W|NdB3phen在开孔条件下呈现反饱和吸收现象,测出双光子吸收系数的值为9.11×10-12 m/W.实验结果表明,NdB3phen的双光子吸收系数和非线性折射率随着光强的增强而增大. 相似文献
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R. Hauber 《Advances in Computational Mathematics》1997,7(4):573-592
This paper investigates retarded differential–algebraic equations of index zero to two with state-dependent delay. The theory
needed to understand the numerical approach and analyze the numerical treatment by collocation methods is developed. Different
strategies for tracking the jump discontinuities are considered and numerical examples are presented to support the convergence
results.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献