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951.
A Combined Experimental and Theoretical Study on the Stereodynamics of Monoaza[5]helicenes: Solvent‐Induced Increase of the Enantiomerization Barrier in 1‐Aza‐[5]helicene 下载免费PDF全文
Prof. Dr. Tullio Caronna Prof. Dr. Andrea Mele Prof. Dr. Antonino Famulari Dr. Daniele Mendola Prof. Dr. Francesca Fontana Dr. Markus Juza Dr. Matthias Kamuf Dr. Kerstin Zawatzky Prof. Dr. Oliver Trapp 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(40):13919-13924
Helicenes and heterohelicenes are attractive compounds with great potential in materials sciences to be used in optoelectronics as ligand backbones in enantioselective catalysis and as chiral sensors. The properties of these materials are related to the stereodynamics of these helical chiral compounds. However, little is known about features controlling stereodynamics in helicenes; in particular, for heterohelicenes the position of the heteroatom could be relevant in this respect. Herein the complete stereodynamic characterization of monoaza[5]helicenes is shown by enantioselective dynamic HPLC and DFT calculations. At variance with previous theoretical calculations, 1‐aza[5]helicene shows a surprisingly high enantiomerization barrier, which is triggered by specific solvent interactions. 相似文献
952.
Cyclotetrabenzoin: Facile Synthesis of a Shape‐Persistent Molecular Square and Its Assembly into Hydrogen‐Bonded Nanotubes 下载免费PDF全文
Qing Ji Ha T. M. Le Dr. Xiqu Wang Dr. Yu‐Sheng Chen Dr. Tatyana Makarenko Prof. Allan J. Jacobson Prof. Ognjen Š. Miljanić 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17205-17209
Cyanide‐catalyzed benzoin condensation of terephthaldehyde produces a cyclic tetramer, which we propose to name cyclotetrabenzoin. Cyclotetrabenzoin is a square‐shaped macrocycle ornamented with four α‐hydroxyketone functionalities pointing away from the central cavity, the dimensions of which are 6.9×6.9 Å. In the solid state, these functional groups extensively hydrogen bond, resulting in a microporous three‐dimensional organic framework with one‐dimensional nanotube channels. This material exhibits permanent—albeit low‐porosity, with a Langmuir surface area of 52 m2 g?1. Cyclotetrabenzoin’s easy and inexpensive synthesis and purification may inspire the creation of other shape‐persistent macrocycles and porous molecular crystals by benzoin condensation. 相似文献
953.
爆炸载荷作用下地下拱形结构动态分析 总被引:14,自引:0,他引:14
应用有限元方法分析了爆炸载荷作用下地下拱形结构与土介质的动力相互作用问题。结构与介质均假定为弹塑性,并用Mises屈服准则描述,且考虑其几何非线性的影响。使用了人为阻尼边界,并使计算模型的几何尺寸满足限制性条件,从而大大提高了计算精度。还对几种解进行了比较,对影响结构应力场的因素也进行了讨论。 相似文献
954.
随机结构正交展开分析的Ritz动力聚缩法 总被引:1,自引:0,他引:1
针对随机结果正交展开理论计算上的弱点 ,本文在分析扩阶矩阵特性的基础上 ,于 Ritz模态向量子空间中对扩阶方程实现动力聚缩 ,大大提高了正交展开理论对实际工程问题的分析能力。分析实例表明 :即使结构参数具有很大变异性 (如δ =0 .4 )时 ,该算法依然能理想地与 Monte Carlo法模拟结果相吻合 ,计算时间则远远小于 Monte Carlo模拟法。同时 ,分析例证再一次强化了在结构动力分析中考虑结构参数随机性的必要性 相似文献
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958.
Nikolai V. Tsvetkov Mariya E. Mikhailova Nina G. Mikusheva Alexey A. Lezov Alexander S. Gubarev Elena V. Lebedeva 《International Journal of Polymer Analysis and Characterization》2017,22(1):27-34
Conformational and dynamo-optical properties of a homologous series of poly(cetyltrimethylammonium 2-acrylamido-2-methylpropane sulfonates) with molecular masses ranging from 80 to 700?kDa were studied in chloroform solutions by viscometry, dynamic light scattering, sedimentation, and flow birefringence. The Mark–Kuhn–Houwink Equations for this polymer in chloroform were obtained; the values of hydrodynamic diameter and the Kuhn segment length as well as the value of intrinsic anisotropy of polarizability of the monomer unit were defined. 相似文献
959.
960.
The resilient dissipative dynamic output feedback control problem for a class of uncertain Markov jump Lur’e systems with piecewise homogeneous transition probabilities and time-varying delays in the discrete-time domain are examined in this study. The designed controller can tolerate additive uncertainties in the controller gain matrix, which result from controller implementations. The time-varying delays are also supposed to be mode-dependent with lower and upper bounds known a priori. By constructing a Lyapunov–Krasovskii functional candidate, the sufficient conditions regarding the existence of desired resilient dissipative controllers are obtained in terms of linear matrix inequalities, thereby ensuring that the resulting closed-loop system is stochastically stable and strictly dissipative. Two numerical examples were established to illustrate the effectiveness of the proposed theoretical results. 相似文献