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201.
Zöller T Iovkova-Berends L Berends T Dietz C Bradtmöller G Jurkschat K 《Inorganic chemistry》2011,50(17):8645-8653
The syntheses and molecular structures of the intramolecularly coordinated tin(II) compounds {CH(2)N(Me)CH(Me)CH(Ph)O}(2)SnL (2, L = lone pair; 4, L = W(CO)(5); 5, L = Cr(CO)(5)) and of the related hydroxido-substituted tin(IV) compound [{CH(2)N(Me)CH(Me)CH(Ph)O}(2)Sn(OH)](2)O, 6a, are reported. Also reported are the molecular structures of the enantiopure N,N'-ethylenebis-(1R,2S)-ephedrine, {CH(2)N(Me)CH(Me)CH(Ph)OH}(2) (1), and its hydrobromide {CH(2)N(Me)CH(Me)CH(Ph)OH}(2)·HBr (1a). 相似文献
202.
Steinberg A Froimowitz M Parrish DA Deschamps JR Glaser R 《The Journal of organic chemistry》2011,76(22):9239-9245
Alkyl analogues of methylphenidate (Ritalin) salts are slow onset, long duration dopamine reuptake inhibitors with a potential use as a cocaine abuse pharmacotherapy. X-ray crystallographic studies and nuclear magnetic resonance (NMR) investigations strongly suggest that avoidance of sterically unfavorable gauche(-)gauche(+) orientations effectively influences both the C(α)-alkyl side chain conformation and the formation of a predominant rotamer about the CH-CH bond ligating piperidine and C(Ar)R moieties. The favored CH-CH rotamer in D(2)O and in CD(2)Cl(2) of the pharmacologically interesting i-Bu and CH(2)-cyc-Pnt (RS,RS)-salts has the same antiperiplanar arrangement that was found in the crystal structures, although there clearly is a fast equilibrium involving smaller amounts of synclinal partners. While the rotamer in the (RS,SR)-i-Bu HCl crystal structure exhibits a synclinal orientation for the vicinal pair of adjacent methine protons, the weighted time-averaged arrangement for these protons becomes almost completely antiperiplanar when the crystals are dissolved in D(2)O. Increased steric congestion around the CH-CH bond in the analogous N-methyl tertiary ammonium salts seems to augment the quantity of the preferred rotamer within the mixture. The stereochemistry of the species observed via NMR seems to arise from specific combinations of N-methyl orientation and avoidance of sterically unfavorable gauche(-)gauche(+) arrangements. 相似文献
203.
Austin KA Herdtweck E Bach T 《Angewandte Chemie (International ed. in English)》2011,50(36):8416-8419
From simple to complex: Starting from easily accessible isoquinolones 1 (X=Br, OH), complex cyclobutane photoproducts such as compound 2 can be obtained with high enantioselectivity (88-96?%?ee) through the use of a chiral template. Compound 3, which was isolated in 53?%?ee starting from a racemic substrate, is the product of a unique, unprecedented kinetic resolution process. 相似文献
204.
Biskup T Hitomi K Getzoff ED Krapf S Koslowski T Schleicher E Weber S 《Angewandte Chemie (International ed. in English)》2011,50(52):12647-12651
Subtle differences in the local sequence and conformation of amino acids can result in diversity and specificity in electron transfer (ET) in proteins, despite structural conservation of the redox partners. For individual ET steps, distance is not necessarily the decisive parameter; orientation and solvent accessibility of the ET partners, and thus the stabilization of the charge-separated states, contribute substantially. 相似文献
205.
Krapf S Schill M Krötz S Koslowski T 《Physical chemistry chemical physics : PCCP》2011,13(33):14973-14983
Motivated by recent progress in the mass spectroscopy of the elementary reaction of alkali metals and water dispersed in ultracold helium nanodroplets (S. Müller et al., Phys. Rev. Lett., 2009, 102, 183401.), we investigate the properties of pure and mixed Cs clusters and cluster ions, Cs(l)H(m)O(n)(0/+), from a quantum chemical perspective. The presence of Cs atoms requires a careful choice of the methodology, which we have tested for small molecules for which experimental results were available. With the thus selected density functional, pseudopotential and basis set, we compute the geometry, the ionization potentials and the atomization energy, enabling a proper estimate of the energetics of cluster fragmentation upon photoionization. Based upon these calculations, we are able to construct a fragmentation tree that rationalizes the origin of all peaks observed in the experimental mass spectrum. Infrared spectra are computed, and we introduce a simple mixed quantum-classical model that essentially reproduces the cluster geometries. 相似文献
206.
We approach the electronic properties of a simple model of organic solar cells, a binary mixture of αα'-oligothiophenes and buckminsterfullerene, from a theoretical and numerical perspective. Close-packed model geometries are generated using a Monte Carlo method, the electronic structure is described by a reparametrized semiempirical Pariser-Parr-Pople Hamiltonian. All electronic properties, such as optical absorption spectra, tightly-bound charge transfer states and exciton bands, arise from the same atomistic Hamiltonian using a configuration interaction method involving single excitations. The absorption spectra are dominated by intramolecular contributions, whereas in the optical gap low-lying charge transfer states are predicted. The efficiency of the solar cell crucially depends on the structure of the charge-transfer exciton bands and on the relaxation mechanism. We discuss how these findings may help improve the design of organic solar cells from an excitonic view. 相似文献
207.
Zirwes Thorsten Zhang Feichi Habisreuther Peter Hansinger Maximilian Bockhorn Henning Pfitzner Michael Trimis Dimosthenis 《Flow, Turbulence and Combustion》2021,107(2):517-517
Flow, Turbulence and Combustion - The article Quasi-DNS Dataset of a Piloted Flame with Inhomogeneous Inlet Conditions written by Thorsten Zirwes, Feichi Zhang, Peter Habisreuther, Maximilian... 相似文献
208.
Large-scale computer simulations are presented to investigate the avalanche statistics of sandpiles using molecular dynamics. We show that different methods of measurement lead to contradictory conclusions, presumably due to avalanches not reaching the end of the experimental table. 相似文献
209.
210.