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Zeitschriftenartikel zum Thema „Achiral and chiral“

Autor: Grafiati

Veröffentlicht am 18. Mai 2024

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1

Rananaware, Anushri, Duong Duc La, Mohammad Al Kobaisi, Rajesh S. Bhosale, Sidhanath V. Bhosale und Sheshanath V. Bhosale. „Controlled chiral supramolecular assemblies of water soluble achiral porphyrins induced by chiral counterions“. Chemical Communications 52, Nr. 67 (2016): 10253–56. http://dx.doi.org/10.1039/c6cc04427a.

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2

Guven, Zekiye P., Burcin Ustbas, Kellen M. Harkness, Hikmet Coskun, Chakra P. Joshi, Tabot M. D. Besong, Francesco Stellacci, Osman M. Bakr und Ozge Akbulut. „Synthesis and characterization of mixed ligand chiral nanoclusters“. Dalton Transactions 45, Nr. 28 (2016): 11297–300. http://dx.doi.org/10.1039/c6dt00785f.

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Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties.

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3

Reyes Calle, Juliana, Jairo Antonio Cubillos Lobo, Consuelo Montes de Correa und Aída Luz Villa Holguín de P. „Oxidising agent and catalyst chirality effect on epoxidation of R-(+)- Limonene using Jacobsen-type catalysts“. Ingeniería e Investigación 28, Nr. 2 (01.05.2008): 37–44. http://dx.doi.org/10.15446/ing.investig.v28n2.14890.

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The oxidising agent effect on R-(+)-Limonene epoxide diastereoselectivity using chiral and achiral Jacobsen’s type catalysts is presented. The type of oxidising agent strongly influences diastereoselectivity. Moderate diastereomeric excesses were achieved in the presence of oxidising agents prepared in situ but in the absence of catalyst (23% for DMD and 29% for O2/pivalaldehyde). Similar diastereomeric excesses were obtained with both chiral and achiral catalyst when the oxidising agents were prepared in situ; 56% and 50% excesses were obtained when using DMD for the chiral and achiral catalyst (respectively) and 38% using O2/pivalaldehyde for both catalysts. Diastereomeric excesses were not observed in the absence of catalyst when using commercial oxidising agents; the chiral catalyst presented larger diastereomeric excesses than its achiral counterpart: 65% and 38% excess using NaOCl for the chiral and achiral catalyst, respectively, and 79% and 39% using m-CPBA for the chiral and achiral catalyst, respectively. This suggests that at least one oxidant species, different from the conventionally accepted (MnV(oxo)), might be involved in this catalytic process. A modification of the traditional catalytic cycle is proposed considering the type of oxidising agent. The catalyst’s chiral centre appears to govern asymmetric induction when commercial oxidising agents are used, whereas the R-(+)-Limonene chiral centre appears to govern asymmetric induction in the presence of in situ-prepared oxidising agents. On the other hand, the chemical stability of Jacobsen’s catalyst improved when in situ produced DMD was used as oxidising agent.

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4

Pakalidou, Nikoletta, David L. Cheung, Andrew J. Masters und Carlos Avendaño. „Macroscopic chiral symmetry breaking in monolayers of achiral nonconvex platelets“. Soft Matter 13, Nr. 45 (2017): 8618–24. http://dx.doi.org/10.1039/c7sm01840a.

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The fabrication of chiral structures using achiral building blocks is a fundamental problem that remains a challenge in materials science. Pictured are local chiral configurations formed by non-convex (achiral) platelets with 6- and 4-fold symmetries.

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5

Wilson, Tyler M., Audra Davis, Reilly E. Sonstrom, Justin L. Neill, Emma A. Ziebarth, Ariel Poulson und Richard E. Carlson. „Essential Oil Composition and Enantioselective Profile of Agastache urticifolia (Lamiaceae) and Monardella odoratissima (Lamiaceae) from Utah“. Molecules 28, Nr. 5 (28.02.2023): 2249. http://dx.doi.org/10.3390/molecules28052249.

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Two species within the Lamiaceae (mint) family, Agastache urticifolia and Monardella odoratissima, are aromatic plants that are native to the Intermountain Region (USA). Essential oil produced through steam distillation was examined to establish the essential oil yield and both the achiral and chiral aromatic profiles of both plant species. The resulting essential oils were analyzed by GC/MS, GC/FID, and MRR (molecular rotational resonance). For A. urticifolia and M. odoratissima, achiral essential oil profiles were largely composed of limonene (71.0%, 27.7%), trans-β-ocimene (3.6%, 6.9%), and pulegone (15.9%, 4.3%), respectively. Between the two species, eight chiral pairs were analyzed and, interestingly, the dominant enantiomer (calculated as ee%) of limonene and pulegone switched between the two species. Where enantiopure standards were not commercially available, MRR was used as a reliable analytical technique for chiral analysis. This study verifies the achiral profile for A. urticifolia and, for the first time to the authors’ knowledge, establishes the achiral profile for M. odoratissima and chiral profile for both species. Additionally, this study confirms the utility and practicality of using MRR for determining chiral profiles in essential oils.

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6

Wang, Lewen, Tengfei He, Hailiang Liao, Yige Luo, Wen Ou, Yinye Yu, Wan Yue, Guankui Long, Xingzhan Wei und Yecheng Zhou. „A Theoretical Design of Chiral Molecules through Conformational Lock towards Circularly Polarized Luminescence“. Photonics 9, Nr. 8 (29.07.2022): 532. http://dx.doi.org/10.3390/photonics9080532.

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Circularly polarized (CP) light has shown great potential in quantum computing, optical communications, and three-dimensional displays. It is still a challenge to produce high-efficiency and high-purity CP light. Herein, we proposed a strategy to design chiral organic small molecules for CP light generation. These kinds of chiral molecules are formed by achiral light-emitting groups and achiral alkyl chains through conformational lock, which indicates that chirality can also be introduced into achiral light-emitting groups through rational molecular design. The chirality of these molecules can be further tuned by changing the length of the alkyl chains connecting the diketopyrrolopyrrole unit. The chiroptical properties of these molecules are confirmed by calculated electronic circular dichroism and chiral emission spectra, and further confirmed in experiments. The strategy developed in this work will greatly enlarge the candidate library of chiral luminescent materials.

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7

Dressel, Christian, Wolfgang Weissflog und Carsten Tschierske. „Spontaneous mirror symmetry breaking in a re-entrant isotropic liquid“. Chemical Communications 51, Nr. 87 (2015): 15850–53. http://dx.doi.org/10.1039/c5cc06843f.

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8

Becalski, Adam, William R. Cullen, Michael D. Fryzuk, Georg Herb, Brian R. James, James P. Kutney, Krystyna Piotrowska und Dianne Tapiolas. „The chemistry of thujone. XII. The synthesis of pyrethroid analogues via chiral cyclopropanation“. Canadian Journal of Chemistry 66, Nr. 12 (01.12.1988): 3108–15. http://dx.doi.org/10.1139/v88-479.

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An extensive study involving achiral and chiral cyclopropanation of various isoprenoid units derived from the monoterpene thujone is presented. Carbenoid intermediates generated from ethyl and L-menthyl diazoacetates and various achiral and chiral copper catalysts are employed to achieve the desired cyclopropanation reaction. It is shown that high levels of enantiomeric excess can be achieved, particularly when L-menthyl diazoacetate and a chiral catalyst are employed. The resultant products are then converted to pyrethroid-like analogues.

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9

Destoop, Iris, Andrea Minoia, Oleksandr Ivasenko, Aya Noguchi, Kazukuni Tahara, Yoshito Tobe, Roberto Lazzaroni und Steven De Feyter. „Transfer of chiral information from a chiral solvent to a two-dimensional network“. Faraday Discussions 204 (2017): 215–31. http://dx.doi.org/10.1039/c7fd00103g.

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Chiral induction in self-assembled monolayers has garnered considerable attention in the recent past, not only due to its importance in chiral resolution and enantioselective heterogeneous catalysis but also because of its relevance to the origin of homochirality in life. Here, we demonstrate the emergence of homochirality in a supramolecular low-density network formed by achiral molecules at the interface of a chiral solvent and an atomically-flat achiral substrate. We focus on the impact of structure and functionality of the adsorbate and the chiral solvent on the chiral induction efficiency in self-assembled physisorbed monolayers, as revealed by scanning tunneling microscopy. Different induction mechanisms are proposed and evaluated, with the assistance of advanced molecular modeling simulations.

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10

Jin, Lei, Xiongyu Liang, Chengmao He, Tiejun Wang, Kun Liang und Li Yu. „Plasmon—Assisted Resonance Energy Transfer Involving Electric and Magnetic Coupling“. Electronics 13, Nr. 8 (19.04.2024): 1566. http://dx.doi.org/10.3390/electronics13081566.

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We develop a quantum theory based on macroscopic quantum electrodynamics to research the resonance energy transfer (RET) between a chiral donor and acceptor. It differs from the previous Green function approach which needs specific boundary conditions to obtain an analytical solution for calculating the RET rate. Our theory can combine the finite-difference time-domain (FDTD) method, which gives a simple and efficient semi-analytical approach, to evaluate the chiral RET rate in an arbitrary plasmonic nanosystem. Applying our theory to the systems of chiral molecules 3-methylcyclopentanone (3MCP) near the achiral/chiral plasmonic nanostructures, the RET process, which is divided into nondiscriminatory and discriminatory parts, is investigated. We find that plasmon will enhance both nondiscriminatory and discriminatory rates compared to the absence of plasmonic nanostructure, but the plasmon supported by chiral nanostructure contributes more to the discriminatory rate. The ratio of discriminatory to nondiscriminatory rates in the system consisting of 3MCP and chiral plasmonic structure is five-fold compared to the system consisting of 3MCP and achiral plasmonic structure. The phenomena can be attributed to the chiral electric-magnetic coupling. Our findings are important in understanding the achiral and chiral electric-magnetic interaction and designing chiral light-harvesting and sensing devices.

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11

Lee, Yen, Boyeong Kang und Jiwon Seo. „Metalloporphyrin Dimers Bridged by a Peptoid Helix: Host-Guest Interaction and Chiral Recognition“. Molecules 23, Nr. 11 (24.10.2018): 2741. http://dx.doi.org/10.3390/molecules23112741.

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Co-facial porphyrins have been designed to construct porphyrin tweezers with versatile molecular recognition capabilities. In this study, we synthesized metalloporphyrin–peptoid conjugates (MPPCs) displaying two metalloporphyrins on a peptoid scaffold with either achiral unfolded (1) or helical (2 and 3) secondary structures. Host–guest complexation of MPPCs was realized with various guests of different lengths and basicities, and the extent of complexation was measured by UV-vis and circular dichroism (CD) spectroscopic titration. Intermolecular and intramolecular chirality induction were observed on achiral and chiral peptoid backbones, respectively. Spectroscopic data indicated that a broad scope of achiral guests can be recognized by chiral 2; in particular, longer and more flexible guests were seen to bind more tightly on 2. In addition, chiral 2 provided a distinct CD couplet with dl-, d-, or l-Lys-OMe, which was a result of the diastereomeric host–guest complex formation. Our results indicated that MPPCs can recognize, contrast, and analyze various achiral, chiral, or racemic molecules. Based on co-facial metalloporphyrins present on peptoid scaffolds, we developed a novel class of porphyrin tweezers, which can be further utilized in asymmetric catalysis, molecular sensing, and drug delivery.

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12

Zhang, Wanning, Hui Chang, Jing Ai, Shunai Che, Yingying Duan und Lu Han. „Spontaneous chiral self-assembly of achiral AIEgens into AIEgen-silica hybrid nanotubes“. Chemical Communications 55, Nr. 96 (2019): 14438–41. http://dx.doi.org/10.1039/c9cc06873b.

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13

Tanaka, Koichi, Takaichi Hiratsuka, Yuko Kojima und Yasuko T. Osano. „Synthesis, Structure and Chiral Inclusion Crystallisation of Tetrakis(4-Ethynylphenyl)Ethylene Derivatives“. Journal of Chemical Research 2002, Nr. 5 (Mai 2002): 209–12. http://dx.doi.org/10.3184/030823402103171889.

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Achiral host molecules, tetrakis(4-ethynylphenyl)ethylene 3 and tetrakis(4-bromoethynylphenyl)ethylene 4, formed chiral host–guest inclusion crystals with achiral guest molecules via weak intermolecular interactions.

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14

Memmer, Reiner, und Folkert Janssen. „Computer Simulation of Chiral Liquid Crystal Phases IX. Chiral Induction in Guest-host Systems - Calculation of the Helical Twisting Power“. Zeitschrift für Naturforschung A 54, Nr. 12 (01.12.1999): 747–54. http://dx.doi.org/10.1515/zna-1999-1212.

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Abstract The chiral induction in liquid crystalline phases was studied by Monte Carlo simulation of the chiral Lebwohl-Lasher model. Binary guest-host systems composed of achiral and chiral molecules as well as of different chiral molecules were investigated in dependence on the composition. A cholesteric phase was induced by dissolving a small fraction of chiral molecules in a nematic phase. For dilute solutions the equilibrium pitch was found to be a linear function of the chiral dopant concentration. Independent of system size effects the application of self-determined boundary conditions enabled the determination of the symmetry adapted quantities for the chiral induction, the helical twisting power (HTP) and the achiral helical twisting power (AHTP). Additionally, a different orientational behaviour of enantiomeric dopants in the chiral surroundings of a cholesteric host phase has been determined.

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15

Liu, Yiyi, Tharaka Perera, Qianqian Shi, Zijun Yong, Sudaraka Mallawaarachchi, Bo Fan, Julia Ann-Therese Walker et al. „Thermoresponsive chiral plasmonic nanoparticles“. Nanoscale 14, Nr. 11 (2022): 4292–303. http://dx.doi.org/10.1039/d1nr08343k.

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Poly(N-isopropylacrylamide) (PNIPAM) has been used to modify chiral plasmonic nanoparticles. The thermoresponsive studies reveal the impact of achiral dielectric nanoenvironment on chiral plasmonic responses.

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16

Royes, Jorge, Víctor Polo, Santiago Uriel, Luis Oriol, Milagros Piñol und Rosa M. Tejedor. „Chiral supramolecular organization from a sheet-like achiral gel: a study of chiral photoinduction“. Physical Chemistry Chemical Physics 19, Nr. 21 (2017): 13622–28. http://dx.doi.org/10.1039/c7cp01739a.

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17

Zhang, Yingjie, und Jianping Deng. „Chiral helical polymer materials derived from achiral monomers and their chiral applications“. Polymer Chemistry 11, Nr. 34 (2020): 5407–23. http://dx.doi.org/10.1039/d0py00934b.

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Helix-sense-selective polymerization (HSSP) of achiral monomers and chiral post-induction of racemic helical polymers provide two alternative approaches for constructing chiral helical polymer materials.

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18

Alexandrov, Anatoly I., und Tamara V. Pashkova. „Structure Investigation of Mesogenic Homo- and Copolymers Based on Chiral and Achiral Acrylates“. Liquid Crystals and their Application 23, Nr. 4 (26.12.2023): 82–93. http://dx.doi.org/10.18083/lcappl.2023.4.82.

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The X-ray diffraction method was used to study the structure of mesogenic homo- and copolymers based on chiral and achiral acrylates (disubstituted biphenyl and phenylbenzoate) under the orienting influence of magnetic and (in some cases) electric fields. The analysis of diffraction patterns was carried out in terms of the Hosemann model of a paracrystal using structural modeling and diffraction calculations on models. It was established that chiral and achiral homopolymers form smectic bilayer polar structures, but the structure of the achiral homopolymer possesses weak polarization due to small value of total dipole moment of C=O groups in the side chains. The copolymers (as the chiral homopolymer) form smectic bilayer polar helicoidal structures. The distribution of chiral and achiral components in the layers of the common bilayer depends on their ratios in the copolymer. In turn, this distribution affects both the step of helicoidal structure and the nature of structural-phase transformations in the copolymers. A comparative evaluation of the orientational effects of magnetic and electric fields on the structure of the chiral homopolymer and the copolymers has been carried out. The analysis of the temperature dependences of diffraction and structural parameters of the investigated polymers allowed us to explain some features of their behaviour within seemingly similar (by the type of X-ray patterns) smectic phases.

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19

Mislow, Kurt. „Absolute Asymmetric Synthesis: A Commentary“. Collection of Czechoslovak Chemical Communications 68, Nr. 5 (2003): 849–64. http://dx.doi.org/10.1135/cccc20030849.

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Absolute asymmetric synthesis, i.e., the formation of enantiomerically enriched products from achiral precursors without the intervention of chiral chemical reagents or catalysts, is in practice unavoidable on statistical grounds alone. That random chance, combined with suitable amplification mechanisms, might ultimately account for biomolecular homochirality in Nature was recognized more than a century ago. Soai and collaborators have recently developed an asymmetric autocatalysis reaction that is capable of amplifying a tiny enantiomeric excess of far below 1% to yield a nearly enantiopure product. Although there is no easy way to tell the difference between an asymmetric autocatalysis reaction initiated by the tiny enantiomeric excess due to random chance and one initiated by minuscule quantities of unidentified chiral impurities, it is nevertheless all but certain that the Soai reaction is capable of producing optically active compounds by an absolute asymmetric synthesis, starting from nominally achiral reagents free of chiral contaminants and run under achiral conditions, e.g., without the intervention of chiral physical forces.

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20

Wang, Chao, Hua Hao, Daisuke Hashizume und Keisuke Tajima. „Surface-induced enantiomorphic crystallization of achiral fullerene derivatives in thin films“. Chemical Science 11, Nr. 18 (2020): 4702–8. http://dx.doi.org/10.1039/d0sc01163k.

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21

Miao, Tengfei, Xiaoxiao Cheng, Haotian Ma, Wei Zhang und Xiulin Zhu. „Induction, fixation and recovery of self-organized helical superstructures in achiral liquid crystalline polymer“. Polymer Chemistry 12, Nr. 41 (2021): 5931–36. http://dx.doi.org/10.1039/d1py01206a.

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22

Wang, Xiongbin, Junjie Hao, Jiaji Cheng, Junzi Li, Jun Miao, Ruxue Li, Yiwen Li et al. „Chiral CdSe nanoplatelets as an ultrasensitive probe for lead ion sensing“. Nanoscale 11, Nr. 19 (2019): 9327–34. http://dx.doi.org/10.1039/c8nr10506e.

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Achiral CdSe NPLs could show chirality through ligand exchange with chiral cysteine molecules. Chiral CdSe NPLs were successfully applied as a chiral probe to detect lead ions with high sensitivity and selectivity.

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23

Park, Changjun, Jinhee Lee, Taehyoung Kim, Jaechang Lim, Jeyoung Park, Woo Youn Kim und Sang Youl Kim. „Homochiral Supramolecular Thin Film from Self-Assembly of Achiral Triarylamine Molecules by Circularly Polarized Light“. Molecules 25, Nr. 2 (18.01.2020): 402. http://dx.doi.org/10.3390/molecules25020402.

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Here, we report the formation of homochiral supramolecular thin film from achiral molecules, by using circularly polarized light (CPL) only as a chiral source, on the condition that irradiation of CPL does not induce a photochemical change of the achiral molecules. Thin films of self-assembled structures consisting of chiral supramolecular fibrils was obtained from the triarylamine derivatives through evaporation of the self-assembled triarylamine solution. The homochiral supramolecular helices with the desired handedness was achieved by irradiation of circularly polarized visible light during the self-assembly process, and the chiral stability of supramolecular self-assembled product was achieved by photopolymerization of the diacetylene moieties at side chains of the building blocks, with irradiation of circularly polarized ultraviolet light. This work provides a novel methodology for the generation of homochiral supramolecular thin film from the corresponding achiral molecules.

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24

Li, Wenfang, Zeyuan Dong, Junyan Zhu, Quan Luo und Junqiu Liu. „Spontaneous formation of organic helical architectures through dynamic covalent chemistry“. Chem. Commun. 50, Nr. 94 (2014): 14744–47. http://dx.doi.org/10.1039/c4cc07263d.

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25

Ramamurthy. „Achiral Zeolites as Reaction Media for Chiral Photochemistry“. Molecules 24, Nr. 19 (02.10.2019): 3570. http://dx.doi.org/10.3390/molecules24193570.

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Obtaining enantiomerically-enriched photoproducts from achiral reactants has been a long-sought goal. The various methods developed to achieve chiral induction in photoproducts during the last fifty years still suffer from a lack of predictability, generality, and simplicity. With the current emphasis on green chemistry, obtaining enantiomerically enriched products via photochemistry is a likely viable alternative for the future. Of the various approaches developed during the last three decades, the one pioneered in the author’s laboratory involved the use of commercially-available and inexpensive achiral zeolites as the media. This approach does not use any solvent for the reaction. Examples from these studies are highlighted in this article. Since no chiral zeolites were available, when the work was initiated in the author’s laboratory, commercially-available zeolites X and Y were modified with chiral inductors so that the reaction space becomes chiral. The results obtained established the value of chirally-modified, commercial zeolites as media for achieving chiral induction in photochemical reactions. A recent report of the synthesis of a chiral zeolite is likely to stimulate zeolite-based chiral photochemistry in synthesizing enantiomerically-pure organic molecules. The availability of chiral zeolites in future is likely to energize research in this area. Our earlier observations on this topic, we believe, would be valuable for progress of the field. Keeping this in mind, I have summarized the work carried out in our laboratory on chiral photochemistry on chirally-modified zeolites. This review does not include examples where high chiral induction has been obtained via a strategy that examines molecules appended with chiral auxiliary within achiral and chirally-modified zeolites. The latter approach yields products with diastereomeric excess >80%.

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26

Štěpánek, Petr, Ondřej Vích, Lukáš Werner, Ladislav Kniežo, Hana Dvořáková und Pavel Vojtíšek. „Stereoselective Preparation of Precursors of α-C-(1→3)-Disaccharides“. Collection of Czechoslovak Chemical Communications 70, Nr. 9 (2005): 1411–28. http://dx.doi.org/10.1135/cccc20051411.

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The stereoselectivity of cycloaddition of sugar-containing substituted 1-(thiazol-2-yl)but-2-en-1-ones 1 and vinyl ethers was studied using the achiral vinyl ether/chiral catalyst as well as the chiral vinyl ether/achiral catalyst combinations. It has been shown that Eu(fod)3-catalyzed cycloaddition of oxadienes 1a-1e with the chiral vinyl ethers 9 and 10 affords stereoselectively almost pure cycloadducts 11a-11e and 12a-12e, respectively. The obtained cycloadducts are suitable precursors for the synthesis of α-C-(1→3)-disaccharides, containing 2-deoxy-arabino-hexopyranose moiety of D- or L-configuration.

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27

MU, WEIHUA, ANTHONY NICKOLAS VAMIVAKAS, YAN FANG und BOLIN WANG. „PHONON DISPERSION IN CHIRAL SINGLE-WALL CARBON NANOTUBES“. Modern Physics Letters B 21, Nr. 25 (30.10.2007): 1667–76. http://dx.doi.org/10.1142/s021798490701419x.

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The method to obtain phonon dispersion of achiral single-wall carbon nanotubes (SWNTs) from 6×6 matrix proposed by Mahan and Jeon7 has been extended to chiral SWNTs. The number of calculated phonon modes of a chiral SWNT (10, 1) is much larger than that of a zigzag one (10, 0) because the number of atoms in the translational unit cell of chiral SWNT is larger than that of an achiral one even though they have relative similar radius. The possible application of our approach to other models with more phonon potential terms beyond Mahan and Jeon's model is discussed.

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28

Imai, Yoshitane. „Generation of Circularly Polarized Luminescence by Symmetry Breaking“. Symmetry 12, Nr. 11 (28.10.2020): 1786. http://dx.doi.org/10.3390/sym12111786.

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Circularly polarized luminescence (CPL) has attracted significant attention in the fields of chiral photonic science and optoelectronic materials science. In a CPL-emitting system, a chiral luminophore derived from chiral molecules is usually essential. In this review, three non-classical CPL (NC-CPL) systems that do not use enantiomerically pure molecules are reported: (i) supramolecular organic luminophores composed of achiral organic molecules that can emit CPL without the use of any chiral auxiliaries, (ii) achiral or racemic luminophores that can emit magnetic CPL (MCPL) by applying an external magnetic field of 1.6 T, and (iii) circular dichroism-silent organic luminophores that can emit CPL in the photoexcited state as a cryptochiral CPL system.

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29

Rusková, Renáta, und Dušan Račko. „Knot Formation on DNA Pushed Inside Chiral Nanochannels“. Polymers 15, Nr. 20 (22.10.2023): 4185. http://dx.doi.org/10.3390/polym15204185.

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We performed coarse-grained molecular dynamics simulations of DNA polymers pushed inside infinite open chiral and achiral channels. We investigated the behavior of the polymer metrics in terms of span, monomer distributions and changes of topological state of the polymer in the channels. We also compared the regime of pushing a polymer inside the infinite channel to the case of polymer compression in finite channels of knot factories investigated in earlier works. We observed that the compression in the open channels affects the polymer metrics to different extents in chiral and achiral channels. We also observed that the chiral channels give rise to the formation of equichiral knots with the same handedness as the handedness of the chiral channels.

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30

Li, Hanbo, Xinshuang Gao, Chenqi Zhang, Yinglu Ji, Zhijian Hu und Xiaochun Wu. „Gold-Nanoparticle-Based Chiral Plasmonic Nanostructures and Their Biomedical Applications“. Biosensors 12, Nr. 11 (01.11.2022): 957. http://dx.doi.org/10.3390/bios12110957.

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As chiral antennas, plasmonic nanoparticles (NPs) can enhance chiral responses of chiral materials by forming hybrid structures and improving their own chirality preference as well. Chirality-dependent properties of plasmonic NPs broaden application potentials of chiral nanostructures in the biomedical field. Herein, we review the wet-chemical synthesis and self-assembly fabrication of gold-NP-based chiral nanostructures. Discrete chiral NPs are mainly obtained via the seed-mediated growth of achiral gold NPs under the guide of chiral molecules during growth. Irradiation with chiral light during growth is demonstrated to be a promising method for chirality control. Chiral assemblies are fabricated via the bottom-up assembly of achiral gold NPs using chiral linkers or guided by chiral templates, which exhibit large chiroplasmonic activities. In describing recent advances, emphasis is placed on the design and synthesis of chiral nanostructures with the tuning and amplification of plasmonic circular dichroism responses. In addition, the review discusses the most recent or even emerging trends in biomedical fields from biosensing and imaging to disease diagnosis and therapy.

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31

Lee, Jae-Jin, und Suk-Won Choi. „Preferential Circularly Polarized Luminescence from a Nano-Segregated Liquid Crystalline Phase Using a Polymerized Twisted Nematic Platform“. Polymers 12, Nr. 11 (29.10.2020): 2529. http://dx.doi.org/10.3390/polym12112529.

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In this study, a polymerized twisted nematic (TN) network was used as an extrinsic chiral platform to overcome the heterogeneity during spontaneous symmetry breaking in a mixed system comprising an achiral bent-core molecule and rod-like mesogen. The TN platform was prepared by photopolymerizing a reactive mesogen dispersed in a low molecular weight liquid crystal with TN orientation. The use of TN orientation to correct the degeneracy in bent-core molecular systems has been previously reported; however, to the best of our knowledge, this is the first study that uses an extrinsic chiral platform of a polymerized TN network. The heterogeneity in the nano-segregated phase of the achiral mixture was suppressed using the extrinsic TN platform with a twisted angle θ of ≥ |±30°|. When an achiral mixture doped with a luminescent guest molecule was refilled into the extrinsic chiral platform, preferential deracemization with one-handedness occurred, corresponding to the handedness of the TN platform. Therefore, circularly polarized luminescence with a preferential handedness can be achieved using this extrinsic chiral platform.

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32

Lee, Hyoung-In. „Spin–Orbital Coupling and Conservation Laws in Electromagnetic Waves Propagating through Chiral Media“. Optics 4, Nr. 1 (18.01.2023): 100–131. http://dx.doi.org/10.3390/opt4010008.

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This study examines the characteristics of the electromagnetic waves that propagate through an unbounded space filled with a homogeneous isotropic chiral medium. The resulting characters are compared to those of the electromagnetic waves propagating through an achiral free space. To this goal, we form energy conservation laws for key bilinear parameters in a chiral case. Due to a nonzero medium chirality, conservation laws turn out to contain extra terms that are linked to the spin–orbit coupling, which is absent for an achiral case. In this way, we identified where the neat hierarchy exhibited by the achiral case among the key bilinear parameters is destroyed by a medium chirality. As an example, we took a plane wave for the chiral case to evaluate those bilinear parameters. Resultantly, the conservation laws for a chiral case are found to reveal inconsistencies among several bilinear parameters that constitute the conservation laws, thereby prompting us to establish partial remedies for formulating proper wave-propagation problems. Therefore, adequate applications of boundary conditions are found to be necessary after examining typical problems available from the literature.

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33

Fu, Jingke, Xiaohong Huo, Bowen Li und Wanbin Zhang. „Cooperative bimetallic catalysis in asymmetric allylic substitution“. Organic & Biomolecular Chemistry 15, Nr. 46 (2017): 9747–59. http://dx.doi.org/10.1039/c7ob02476b.

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34

Zhang, Qingfeng, Taylor Hernandez, Kyle W. Smith, Seyyed Ali Hosseini Jebeli, Alan X. Dai, Lauren Warning, Rashad Baiyasi et al. „Unraveling the origin of chirality from plasmonic nanoparticle-protein complexes“. Science 365, Nr. 6460 (26.09.2019): 1475–78. http://dx.doi.org/10.1126/science.aax5415.

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Plasmon-coupled circular dichroism has emerged as a promising approach for ultrasensitive detection of biomolecular conformations through coupling between molecular chirality and surface plasmons. Chiral nanoparticle assemblies without chiral molecules present also have large optical activities. We apply single-particle circular differential scattering spectroscopy coupled with electron imaging and simulations to identify both structural chirality of plasmonic aggregates and plasmon-coupled circular dichroism induced by chiral proteins. We establish that both chiral aggregates and just a few proteins in interparticle gaps of achiral assemblies are responsible for the ensemble signal, but single nanoparticles do not contribute. We furthermore find that the protein plays two roles: It transfers chirality to both chiral and achiral plasmonic substrates, and it is also responsible for the chiral three-dimensional assembly of nanorods. Understanding these underlying factors paves the way toward sensing the chirality of single biomolecules.

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35

Harris, Robert A. „Chiral fluctuations in achiral systems“. Journal of Chemical Physics 115, Nr. 23 (15.12.2001): 10577–80. http://dx.doi.org/10.1063/1.1427024.

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36

STINSON, STEPHEN. „Achiral ligands abet chiral catalysis“. Chemical & Engineering News 78, Nr. 10 (06.03.2000): 14. http://dx.doi.org/10.1021/cen-v078n010.p014.

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37

Flack, Howard D. „Chiral and Achiral Crystal Structures“. Helvetica Chimica Acta 86, Nr. 4 (April 2003): 905–21. http://dx.doi.org/10.1002/hlca.200390109.

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38

Geng, Bin, Ling-Xiang Guo, Bao-Ping Lin, Patrick Keller, Xue-Qin Zhang, Ying Sun und Hong Yang. „Side chain liquid crystalline polymers with an optically active polynorbornene backbone and achiral mesogenic side groups“. Polymer Chemistry 6, Nr. 29 (2015): 5281–87. http://dx.doi.org/10.1039/c5py00651a.

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This work describes a series of side-on and end-on SCLCPs with an optically active polynorbornene main chain and achiral mesogens. The side-on SCLCPs tend to form achiral mesophases, while their comparative end-on analogues exhibit chiral mesophases.

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39

Reddy, Kumbam Lingeshwar, Jikson Pulparayil Mathew, Sonia Maniappan, Catherine Tom, Elizabeth Shiby, Ravi Kumar Pujala und Jatish Kumar. „Mandelic acid appended chiral gels as efficient templates for multicolour circularly polarized luminescence“. Nanoscale 14, Nr. 13 (2022): 4946–56. http://dx.doi.org/10.1039/d1nr08506a.

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40

Fernández, Zulema, Berta Fernández, Emilio Quiñoá, Ricardo Riguera und Félix Freire. „Chiral information harvesting in helical poly(acetylene) derivatives using oligo(p-phenyleneethynylene)s as spacers“. Chemical Science 11, Nr. 27 (2020): 7182–87. http://dx.doi.org/10.1039/d0sc02685a.

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41

Mou, Qi, Ruyuan Zhao, Ruihan Niu, Seiya Fukagawa, Taiki Shigeno, Tatsuhiko Yoshino, Shigeki Matsunaga und Bo Sun. „Cp*Ir(iii)/chiral carboxylic acid-catalyzed enantioselective C–H alkylation of ferrocene carboxamides with diazomalonates“. Organic Chemistry Frontiers 8, Nr. 24 (2021): 6923–30. http://dx.doi.org/10.1039/d1qo01344k.

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An achiral Cp*Ir(iii)/chiral carboxylic acid-catalysed enantioselective C–H alkylation of ferrocene carboxamides with diazomalonates was achieved, providing planar chiral alkylated ferrocenes in up to 94 : 6 er.

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42

Zinna, Francesco, Lorenzo Arrico, Tiziana Funaioli, Lorenzo Di Bari, Mariacecilia Pasini, Chiara Botta und Umberto Giovanella. „Modular chiral Eu(iii) complexes for efficient circularly polarized OLEDs“. Journal of Materials Chemistry C 10, Nr. 2 (2022): 463–68. http://dx.doi.org/10.1039/d1tc05023k.

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Chiral lanthanide complexes can be prepared by choosing the achiral antenna ligand and the chiral inducer independently. With this modular approach, complexes optimized for use in efficient CP-OLEDs may be obtained.

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43

Han, Yun-Hu, Yue-Cheng Liu, Xiu-Shuang Xing, Chong-Bin Tian, Ping Lin und Shao-Wu Du. „Chiral template induced homochiral MOFs built from achiral components: SHG enhancement and enantioselective sensing of chiral alkamines by ion-exchange“. Chemical Communications 51, Nr. 77 (2015): 14481–84. http://dx.doi.org/10.1039/c5cc05566k.

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A homochiral anionic framework built from achiral components was synthesized for enantioselective sensing of chiral alkamines. Ion-exchange with polar or chiral organic cations leads to the enhancement of the SHG efficiency.

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44

Pan, Chongqing, Si-Yong Yin, Qing Gu und Shu-Li You. „CpxM(iii)-catalyzed enantioselective C–H functionalization through migratory insertion of metal–carbenes/nitrenes“. Organic & Biomolecular Chemistry 19, Nr. 34 (2021): 7264–75. http://dx.doi.org/10.1039/d1ob01248g.

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In this review, we highlight the developments in chiral CpxM(iii) complexes or achiral CpxM(iii) complexes/chiral carboxylic acid-catalyzed enantioselective C–H functionalization reactions through migratory insertion of metal–carbenes/nitrenes.

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45

Schuette, Jodi M., A. Yvette Will, Rezik A. Agbaria und Isiah M. Warner. „Fluorescence Characterization of the Cyclodextrin/Pyrene Complex Interaction with Chiral Alcohols and Diols“. Applied Spectroscopy 48, Nr. 5 (Mai 1994): 581–86. http://dx.doi.org/10.1366/0003702944924934.

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The chiral properties of cyclodextrins (CDs) facilitate the formation of diastereomeric complexes with a number of pesticides and pharmaceuticals which are also frequently composed of one or more chiral centers. The roles of chirality and structural volume in CD binding to a homologous series of linear, chiral alcohols and diols are evaluated by comparing the trend in the pyrene fluorescence I/III band ratio and the hydrophobicity for the CD/pyrene complex with CD/pyrene complexes incorporating achiral alcohols. Stronger hydrophobicity is observed for complexes capped by chiral alcohols relative to complexes formed with a similar achiral counterpart, suggesting the importance of the alcohol chiral center. Furthermore, the diols induce a more hydrophobic environment than their alcohol counterparts with the β-CD/pyrene complex, while the converse is the case for the γ-CD systems. The systems involving γ-CD were also compared by use of pyrene fluorescence lifetime measurements.

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46

Guerrero, M. M. López, A. Navas Díaz, F. García Sánchez und H. Corrall. „Chiral and Achiral Enantiomeric Separation of (±)-Alprenolol“. Open Chemistry 17, Nr. 1 (12.06.2019): 429–37. http://dx.doi.org/10.1515/chem-2019-0049.

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AbstractThe chiral separation of enantiomers is crucial for pharmacovigilance within drug discovery. Although a large number of prescribed medications are marketed as pure enantiomers, this is not always the case and many are in fact racemic mixtures. Drug scandals, such as that of Thalidomide in 1961, provide a clear example of the social and economic repercussions that can be caused by negligence of these chiral compounds. Two high performance liquid chromatography (HPLC) methods are presented to determine, separate and quantitate a commonly prescribed chiral beta blocker, (-)-Alprenolol. The first method utilises a chiral column to physically separate the two enantiomers of Alprenolol in 25 minutes, before quantitating with two detectors. Fluorimetry gave the better limit of detection of 0.16-0.41ng and a correlation coefficient of 0.999. The second method used an achiral column coupled with polarimetry to quantitate (-)-Alprenolol without the need for physical separation in 10 minutes. The limit of detection achieved was 27-37μg and demonstrated a correlation coefficient of -0.999.

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47

Krekic, Szilvia, Mark Mero, Michel Kuhl, Kannan Balasubramanian, András Dér und Zsuzsanna Heiner. „Photoactive Yellow Protein Adsorption at Hydrated Polyethyleneimine and Poly-l-Glutamic Acid Interfaces“. Molecules 28, Nr. 10 (13.05.2023): 4077. http://dx.doi.org/10.3390/molecules28104077.

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Chiral and achiral vibrational sum-frequency generation (VSFG) spectroscopy was performed in the 1400–1700 and 2800–3800 cm−1 range to study the interfacial structure of photoactive yellow protein (PYP) adsorbed on polyethyleneimine (PEI) and poly-l-glutamic acid (PGA) surfaces. Nanometer-thick polyelectrolyte layers served as the substrate for PYP adsorption, with 6.5-pair layers providing the most homogeneous surfaces. When the topmost material was PGA, it acquired a random coil structure with a small number of β2-fibrils. Upon adsorption on oppositely charged surfaces, PYP yielded similar achiral spectra. However, the VSFG signal intensity increased for PGA surfaces with a concomitant redshift of the chiral Cα-H and N–H stretching bands, suggesting increased adsorption for PGA compared to PEI. At low wavenumbers, both the backbone and the side chains of PYP induced drastic changes to all measured chiral and achiral VSFG spectra. Decreasing ambient humidity led to the loss of tertiary structure with a re-orientation of α-helixes, evidenced by a strongly blue-shifted chiral amide I band of the β-sheet structure with a shoulder at 1654 cm−1. Our observations indicate that chiral VSFG spectroscopy is not only capable of determining the main type of secondary structure of PYP, i.e., β-scaffold, but is also sensitive to tertiary protein structure.

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48

Wang, Juan, Zhen Wei, Fengwan Guo, Chenyang Li, Pengfei Zhu und Wenhua Zhu. „Homochiral 3D coordination polymer with unprecedented three-directional helical topology from achiral precursor: synthesis, crystal structure, and luminescence properties of uranyl succinate metal–organic framework“. Dalton Transactions 44, Nr. 31 (2015): 13809–13. http://dx.doi.org/10.1039/c5dt02111a.

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49

Katoono, Ryo, Keiichi Kusaka, Yuki Saito, Kazuki Sakamoto und Takanori Suzuki. „Chiral diversification through the assembly of achiral phenylacetylene macrocycles with a two-fold bridge“. Chemical Science 10, Nr. 18 (2019): 4782–91. http://dx.doi.org/10.1039/c9sc00972h.

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50

Carballo, Rosa, Alfonso Castiñeiras, Berta Covelo, Ana B. Lago, Ezequiel M. Vázquez-López, Olaya Gómez-Paz, Susana Balboa und Inmaculada Prieto. „Chiral and achiral 1D copper(ii) coordination polymers based on glycolato and chelating aromatic diamine ligands“. CrystEngComm 20, Nr. 17 (2018): 2455–64. http://dx.doi.org/10.1039/c8ce00279g.

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