Strukturübergänge in Clustern

Hartke, Bernd

doi:10.1002/1521-3757(20020503)114:9<1534::aid-ange1534>3.0.co;2-s

Cited by 11 publications

(5 citation statements)

References 281 publications

(212 reference statements)

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“…Before presenting further key results, we would like to point out that EA methods such as those used here do not provide just a single “best” structure but a large set of low‐energy structures. Via built‐in diversity enforcements, we ensure that this set does not contain only identical copies or minor variations of the best structure. Unless noted otherwise, the results presented here are typical for the lowest energy structures in this set, including the best one.…”

Section: Resultsmentioning

confidence: 99%

“…This entailed a demand for theoretical methods that can find optimal three‐dimensional arrangements of atoms or molecules in a huge search space increasing exponentially with particle number. This demand was met with a wide variety of nondeterministic global optimization methods, for example, simulated annealing, Monte‐Carlo (MC) with minimization (also known as basin‐hopping), and genetic/evolutionary algorithms (GA, EA) …”

Section: Introductionmentioning

confidence: 99%

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Exploring self‐organization of molecular tether molecules on a gold surface by global structure optimization

2019

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We employ nondeterministic global cluster structure optimization, based on the evolutionary algorithms paradigm, to model the self-assembly of complex molecules on a surface. As a real-life application example directly related to many recent experiments, we use this approach for the assembly of triazatriangulene "platform" molecules on the Au(111) surface. Without additional restrictions like spatial discretizations, coarse-graining or precalculated adsorption poses, and despite the proof-of-principle character of this study, we achieve satisfactory qualitative agreement with several experimental observations and can provide answers to questions that experiments on these species had left open so far.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Exploring self‐organization of molecular tether molecules on a gold surface by global structure optimization

2019

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“…To obtain reliable global minima for the stoichiometric clusters [(V 2 O 5 ) n A C H T U N G T R E N N U N G (SiO 2 ) m ] + , the geometry optimizations were performed starting from a high number of possible candidate structures (more than 200 for each cluster) generated from a systematic search based on the topological structures, and also a simplified basin-hopping method, [86] the details of which are described in the Supporting Information. Further computations using special methods, such as the strict basin-hopping method or genetic algorithm, [20,87,88] may be necessary to confirm that our search was sufficient to obtain the global minima. + + C 2 H 4 !…”

Section: Methodsmentioning

confidence: 98%

Hydrogen‐Atom Abstraction from Methane by Stoichiometric Vanadium–Silicon Heteronuclear Oxide Cluster Cations

Ding

Zhao

et al. 2010

Chemistry A European J

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Vanadium-silicon heteronuclear oxide cluster cations were prepared by laser ablation of a V/Si mixed sample in an O(2) background. Reactions of the heteronuclear oxide cations with methane in a fast-flow reactor were studied with a time-of-flight (TOF) mass spectrometer to detect the cluster distribution before and after the reactions. Hydrogen abstraction reactions were identified over stoichiometric cluster cations [(V(2)O(5))(n)(SiO(2))(m)](+) (n=1, m=1-4; n=2, m=1), and the estimated first-order rate constants for the reactions were close to that of the homonuclear oxide cluster V(4)O(10) (+) with methane. Density functional calculations were performed to study the structural, bonding, electronic, and reactivity properties of these stoichiometric oxide clusters. Terminal-oxygen-centered radicals (O(t)*) were found in all of the stable isomers. These O(t)* radicals are active sites of the clusters in reaction with CH(4). The O(t)* radicals in [V(2)O(5)(SiO(2))(1-4)](+) clusters are bonded with Si rather than V atoms. All the hydrogen abstraction reactions are favorable both thermodynamically and kinetically. This work reveals the unique properties of metal/nonmetal heteronuclear oxide clusters, and may provide new insights into CH(4) activation on silica-supported vanadium oxide catalysts.

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“…It has been shown that such coverage is necessary for a quantitatively correct description of solvation 41. Global cluster‐structure optimization32, 34 was used to generate optimal conformations of these 50 explicit water molecules, by employing the program package OGOLEM33 and multiple runs per case (five for the reactant complex, transition state, and product complex). To maintain a reasonable balance between accuracy and sufficient conformational exploration of the search space, these global structure optimizations were performed at the force‐field level, by using the OPLS‐AA force field for the reaction center and the TIP4P water model.…”

Section: Methods and Techniquesmentioning

confidence: 99%

Total Synthesis and Biological Assessment of (−)‐Exiguolide and Analogues

Fuwa

Suzuki

Kubo

et al. 2011

Chemistry A European J

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We describe herein an enantioselective total synthesis of (-)-exiguolide, the natural enantiomer. The methylene bis(tetrahydropyran) substructure was efficiently synthesized by exploiting olefin cross-metathesis for the assembly of readily available acyclic segments and intramolecular oxa-conjugate cyclization and reductive etherification for the formation of the tetrahydropyran rings. The 20-membered macrocyclic framework was constructed in an efficient manner by means of Julia-Kocienski coupling and Yamaguchi macrolactonization. Finally, the (E,Z,E)-triene side chain was introduced stereoselectively via Suzuki-Miyaura coupling to complete the total synthesis. Assessment of the growth inhibitory activity of synthetic (-)-exiguolide against a panel of human cancer cell lines elucidated for the first time that this natural product is an effective antiproliferative agent against the NCI-H460 human lung large cell carcinoma and the A549 human lung adenocarcinoma cell lines. Moreover, we have investigated structure-activity relationships of (-)-exiguolide, which elucidated that the C5-methoxycarbonylmethylidene group and the length of the side chain are important for the potent activity.

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Strukturübergänge in Clustern

Cited by 11 publications

References 281 publications

Exploring self‐organization of molecular tether molecules on a gold surface by global structure optimization

Exploring self‐organization of molecular tether molecules on a gold surface by global structure optimization

Hydrogen‐Atom Abstraction from Methane by Stoichiometric Vanadium–Silicon Heteronuclear Oxide Cluster Cations

Total Synthesis and Biological Assessment of (−)‐Exiguolide and Analogues

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