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41.
42.
Exciton‐Vibrational Couplings in Homo‐ and Heterodimer Stacks of Perylene Bisimide Dyes within Cyclophanes: Studies on Absorption Properties and Theoretical Analysis
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David Bialas Christoph Brüning Dr. Felix Schlosser Dr. Benjamin Fimmel Johannes Thein Prof. Dr. Volker Engel Prof. Dr. Frank Würthner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):15011-15018
The optical properties of a series of three cyclophanes comprising either identical or different perylene bisimide (PBI) chromophores were studied by UV/Vis absorption spectroscopy and their distinctive spectral features were analyzed. All the investigated cyclophanes show significantly different absorption features with respect to the corresponding constituent PBI monomers indicating strong coupling interactions between the PBI units within the cyclophanes. DFT calculations suggest a π‐stacked arrangement of the PBI units at close van der Waals distance in the cyclophanes with rotational displacement. Simulations of the absorption spectra based on time‐dependent quantum mechanics properly reproduced the experimental spectra, revealing exciton‐vibrational coupling between the chromophores both in homo‐ and heterodimer stacks. The PBI cyclophane comprising two different PBI chromophores represents the first example of a PBI heterodimer stack for which the exciton coupling has been investigated. The quantum dynamics analysis reveals that exciton coupling in heteroaggregates is indeed of similar strength as for homoaggregates. 相似文献
43.
First full-relativistic density functional calculations with the extension of the spin-polarization functional for the relativistic density functional theory in their collinear and noncollinear form are presented here for the molecular system Pt2. The agreement with experiment is very good. 相似文献
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Polymorphic transitions of HgSexTe(1 ? x) induced by pressure were investigated for 0 <- x <- 1. The transitions were followed by both volume and resistivity measurements on samples of different alloy compositions and of different textures. The transition pressure seems to be a linear function of the alloy composition. 相似文献
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The reconstructed Au(100) surface has been investigated using He-diffraction techniques. The topmost layer is found to have a dominant (1 × 5) periodicity, whereby the corrugation appears one-dimensional in the direction of the longer unit cell. The complex LEED patterns observed for this surface must be due to secondary structural features such as minor atomic displacements in the topmost or lower layers. Several reconstruction models were considered and surface electron density calculations were performed to enable a comparison with the corrugation functions deduced from the He-diffraction data. 相似文献
49.
Zusammenfassung Am Beispiel des Systems Na4(VO3)4-NaCl-H2O wird untersucht, in welcher Weise Ultrazentrifugenmessungen im Sedimentationsgleichgewicht durchgeführt werden müssen, um die molare Masse und die Ladungszahl von Polymerelektrolyten in ternären Systemen unter der Bedingung von nicht vernachlässigbaren Wechselwirkungen zwischen Polymerund Fremdelektrolyt zu bestimmen. Es erweist sich, daß die experimentellen scheinbaren molaren Massen nicht nur auf die Polymerkonzentration Null extrapoliert werden müssen, sondern auch auf die Fremdelektrolytkonzentration Null. Es gelingt, die Ableitung (alnyPXz/amBx)mPXz an der StellemPXz = 0 mol kg-1 mit einer scheinbaren mittleren Ladungszahlz
app
des Polymeranions zu korrelieren. Zwischen dieser und der stöchiometrischen Ladungszahlz des Polymeranions besteht die Beziehungz
app
= Z =az, so daß die Dissoziationskonstante des Polymerelektrolyten für die summarische Dissoziation berechnet werden kann. Die aus dieser Korrelation folgenden Abhängigkeiten der scheinbaren mittleren Ladungszahlen und der Ableitung (alnypx
z
/amBX)Mpx
z
= 0 von der Konzentration des Fremdelektrolyten werden experimentell bestätigt.
Mit 4 Abbildungen und 4 Tabellen 相似文献
Summary The system Na4(VO3)4-NaCl-H20 is taken as an example for ultracentrifugal measurements at sedimentation equilibrium to determine the molar mass and the valency of a polymer electrolyte in a ternary system when interactions exist between the polymer and the supporting electrolyte. The experimental apparent molar mass is obtained by extrapolation to zero value of concentration of both the polymeric and supporting electrolyte. It is possible to correlate the quantity (alnyPX z /amBX)mPXz at the point m PX z = 0 mole kg-1 with the apparent valency zapp of the polymeric anion.z app is related to the stoichiometric valency by the equationz app = z =a.Z. Thus the dissociation constant can be calculated for complete dissociation of the polymer electrolyte. The dependence of zapp and (aln y PX z /a m BX ) m PX z = 0 on concentration of the supporting electrolyte called for in the correlation is verified experimentally.
Mit 4 Abbildungen und 4 Tabellen 相似文献
50.
We develop a theory of extrinsic spin currents in semiconductors, resulting from spin-orbit coupling at charged scatterers, which leads to skew-scattering and side-jump contributions to the spin-Hall conductivity. Applying the theory to bulk n-GaAs, without any free parameters, we find spin currents that are in reasonable agreement with experiments by Kato et al. [Science 306, 1910 (2004)]. 相似文献