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51.
Facchetti A Yoon MH Stern CL Hutchison GR Ratner MA Marks TJ 《Journal of the American Chemical Society》2004,126(41):13480-13501
The synthesis, comparative physicochemical properties, and solid-state structures of five oligothiophene (nT) series differing in substituent nature and attachment, regiochemistry, and oligothiophene core length (n) are described. These five series include the following 25 compounds: (i) alpha,omega-diperfluorohexyl-nTs 1 (DFH-nTs, n = 2-6), (ii) beta,beta'-diperfluorohexyl-nTs 2 (isoDFH-nTs, n = 2-6), (iii) alpha,omega-dihexyl-nTs 3 (DH-nTs, n = 2-6), (iv) beta,beta'-dihexyl-nTs 4 (isoDH-nTs, n = 2-6), and (v) unsubstituted oligothiophenes 5 (alphanTs, n = 2-6). All new compounds were characterized by elemental analysis, mass spectrometry, and multinuclear NMR spectroscopy. To probe and address quantitatively how the chemistry and regiochemistry of conjugated core substitution affects molecular and solid-state properties, the entire 1-5 series was investigated by differential scanning calorimetry, thermogravimetric analysis, and optical absorption and emission spectroscopies. Single-crystal X-ray diffraction data for several fluorocarbon-substituted oligomers are also presented and compared. The combined analysis of these data indicates that fluorocarbon-substituted nT molecules strongly interact in the condensed state, with unit cell level phase separation between the aromatic core and fluorocarbon chains. Surprisingly, despite these strong intermolecular interactions, high solid-state fluorescence efficiencies are exhibited by the fluorinated derivatives. Insight into the solution molecular geometries and conformational behavior are obtained from analysis of optical and variable-temperature NMR spectra. Finally, cyclic voltammetry data offer a reliable picture of frontier MO energies, which, in combination with DFT computations, provide key information on relationships between oligothiophene substituent effects and electronic response properties. 相似文献
52.
Brown AM Ovchinnikov MV Stern CL Mirkin CA 《Journal of the American Chemical Society》2004,126(44):14316-14317
A novel reaction involving the halide-induced rearrangement of ligands within supramolecular Rh(I) complexes containing hemilabile ligands is presented. Three analogous bis- and trishemilabile ligands have been synthesized to construct bi- and trimetallic Rh(I) macrocyclic complexes. An intentionally added halide source results in the formal rotation of only one hemilabile ligand along the axis that is perpendicular to the plane defined by the aryl backbone of the hemilabile ligands. X-ray structures, as determined by X-ray crystallography, of key intermediates and products are presented. 相似文献
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Yang UK Adams T Alton A Arroyo CG Avvakumov S de Barbaro L de Barbaro P Bazarko AO Bernstein RH Bodek A Bolton T Brau J Buchholz D Budd H Bugel L Conrad J Drucker RB Fleming BT Formaggio JA Frey R Goldman J Goncharov M Harris DA Johnson RA Kim JH King BJ Kinnel T Koutsoliotas S Lamm MJ Marsh W Mason D McFarland KS McNulty C Mishra SR Naples D Nienaber P Romosan A Sakumoto WK Schellman H Sciulli FJ Seligman WG Shaevitz MH Smith WH Spentzouris P Stern EG Suwonjandee N Vaitaitis A Vakili M Yu J 《Physical review letters》2001,86(13):2742-2745
We report on the extraction of the structure functions F2 and DeltaxF(3) = xF(nu)(3)-xF(nu;)(3) from CCFR nu(mu)-Fe and nu;(mu)-Fe differential cross sections. The extraction is performed in a physics model-independent (PMI) way. This first measurement of DeltaxF(3), which is useful in testing models of heavy charm production, is higher than current theoretical predictions. The ratio of the F2 (PMI) values measured in nu(mu) and mu scattering is in agreement (within 5%) with the predictions of next-to-leading-order parton distribution functions using massive charm production schemes, thus resolving the long-standing discrepancy between the two sets of data. 相似文献
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Sun R Colin E Ajitanand NN Alexander JM Barton MA DeYoung PA Drake KL Elmaani A Gelderloos CJ Gualtieri EE Guinet D Hannuschke S Jaasma JA Kowalski L Lacey RA Lauret J Norbeck E Pak R Peaslee GF Stern M Stone NT Sundbeck SD Vander Molen AM Westfall GD Yang LB Yee J 《Physical review letters》2000,84(1):43-46
For central collisions of (17-115)A MeV 40Ar+Cu, Ag, Au, an overall balance is determined for the average mass, energy, and longitudinal momentum. Light charged particles and fragments are separated into forward-focused and isotropic components in the frame of the heaviest fragment. Energy removal by the isotropic component reaches 1-2 GeV. For such high deposition energies, statistical multifragmentation models predict much more extensive nuclear disassembly than is observed. 相似文献
56.
We study the transport properties of pinned striped quantum Hall phases. We show that, under quite general assumptions, the macroscopic conductivity tensor satisfies a semicircle law. In particular, this result is valid for both smectic and nematic stripe phases, independent of the presence of topological and orientational defects such as dislocations and grain boundaries. As a special case, our results explain the experimental validity of a product rule for the dissipative part of the resistivity tensor, which was previously derived by MacDonald and Fisher (cond-mat/9907278) for a perfect stripe structure. 相似文献
57.
Vortical structures and instability mechanisms of the unsteady free surface wave-induced separation around a surface-piercing NACA0024 foil at a Froude number of 0.37 and a Reynolds number of 1.52×106 are studied using an unsteady Reynolds-averaged Navier–Stokes (URANS) code with a blended k?ε/k?ω turbulence model and a free surface tracking method. At the free surface, the separated flow reattaches to the foil surface resulting in a wall-bounded separation bubble. The mean and instantaneous flow topologies in the separation region are similar to the owl-face pattern. The initial shear-layer instability, the Karman-like instability, and the flapping instability are identified, and their scaling and physical mechanisms are studied. Validation with experimental fluid dynamics (EFD) and comparison with complementary detached-eddy simulation (DES) indicate that URANS resolves part of the organized oscillations due to the large-scale unsteady vortical structures and instabilities, thereby capturing the gross features of the unsteady separation. The URANS solutions show an initial amplitude defect of 30% for the free surface oscillations where the shear layer separates, and the defect progressively increases downstream as URANS rapidly dissipates the rolled up vortices. 相似文献
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