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Chiral Structure (chiral + structure)
Selected AbstractsA Chiral Metal,Organic Framework Based on Heptanuclear Zinc CoresEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2009Hai-Yang Liu Abstract Two zinc(II) complexes, [Zn9(L1)6(H2O)2]·13.5H2O (1) and [Zn9(L2)6(H2O)3]·C2H5OH·8.5H2O (2), were synthesized. Both 1 and 2 are constructed from molecular building units (MBUs) that contain heptanuclear zinc clusters as cores. By introducing an additional chiral site into the original ligand, we achieved the transformation of the MOF from a nonchiral to a chiral structure, which provides a new strategy for designing chiral compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Raman optical activity of an achiral element in a chiral environmentJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2009Andrew M. Smith Abstract Raman optical activity (ROA) is a relatively new technique used to determine the structure of chiral molecules and is proving useful in the study of biological molecules such as proteins and DNA/RNA. Here, for the first time, we demonstrate the applicability of ROA as a technique to study achiral groups in chiral environments, detecting the induced chirality of N -(fluorenyl-9-methoxycarbonyl) (Fmoc) in a chiral self-assembled structure of Fmoc-dipeptides. This technique is therefore of interest to those studying self-assembled systems that adopt a chiral structure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Global and local linear buckling behavior of a chiral cellular structurePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2005A. Spadoni Abstract This paper investigates the flat-wise compression behavior of an innovative cellular structure configuration. The considered layout has a hexagonal chiral geometry featuring cylinders, or nodes, joined by ligaments, or ribs. The resulting assembly is characterized by a number of interesting properties that can be exploited for the design of alternative honeycombs or cellular topologies to be used in sandwich construction. The flat-wise strength of the chiral geometry is investigated through classical analytical formulas for the linear buckling of thin plates and shells and a bifurcation analysis performed on a Finite Element model. The analytical expressions predict the global buckling behavior and the resulting critical loads, and can be directly compared with the results obtained from the Finite Element analysis. In addition, the Finite Element model predicts local buckling modes, which should be considered to evaluate the possible development of localized plasticity. A sensitivity study is performed to evaluate the influence of the geometry of the chiral structure on its buckling strength. The study shows that the considered topology can offer great design flexibility, whereby several parameters can be selected and modified to improve the flat-wise performance. The comparison with traditional, hexagonal centro-symmetric structural configurations concludes the paper and demonstrates the enhanced performance and the potentials of chiral noncentro-symmetric designs. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Chiral determination: direct interpretation of convergent-beam electron diffraction patterns using the series expansion of Cowley and MoodieACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2007Andrew W. S. Johnson Given a small number of structure factors of a known chiral structure of unknown hand, it is shown that the hand can be determined from the sign of the contrast difference of two reflections in a suitably oriented convergent-beam electron diffraction (CBED) pattern. A simple formula for this difference, which takes into account all the significant second-order scattering, is derived using the series expansion of Cowley and Moodie for n -beam diffraction. The reason for the success of a three-beam interpretation is investigated. The method is applied to patterns from thin crystals in which a mirror projection symmetry can be found and its validity is demonstrated by agreement with experiment using samples of known hand. The advantages of recording patterns near major zone axes are discussed as well as some other experimental aspects of chiral determination using CBED. [source] | ||||||||||