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81.
Jean Thusek Marvin Hoffmann Dr. Olaf Hübner Olena Tverskoy Prof. Uwe H. F. Bunz Prof. Andreas Dreuw Prof. Hans-Jörg Himmel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(66):15147-15154
N-Heteropolycycles are attractive as materials in organic electronic devices. However, a detailed understanding of the low-energy electronic excitation characteristics of these species is still lacking. In this work, the matrix isolation technique is applied to obtain high-resolution absorbance spectra for a series of tetracene and core-substituted N-analogues. The experimental electronic excitation spectra obtained for matrix-isolated molecules are then analysed with the help of quantum-chemical calculations. Additional lower energy excitation bands in the spectrum of the core-substituted N-derivatives of tetracene could be explained in terms of intensity borrowing from dipole-forbidden transitions due to Herzberg–Teller vibronic coupling. In the case of tetracene, evidence for the additional formation of London dimers (J aggregates) is found at higher tetracene concentrations in the matrix. 相似文献
82.
Sebastian N. Intorp Manuel Hodecker Matthias Müller Olena Tverskoy Marco Rosenkranz Evgenia Dmitrieva Alexey A. Popov Frank Rominger Jan Freudenberg Andreas Dreuw Uwe H. F. Bunz 《Angewandte Chemie (International ed. in English)》2020,59(30):12396-12401
Quinoidal azaacenes with almost pure diradical character (y=0.95 to y=0.99) were synthesized. All compounds exhibit paramagnetic behavior investigated by EPR and NMR spectroscopy, and SQUID measurements, revealing thermally populated triplet states with an extremely low‐energy gap ΔEST′ of 0.58 to 1.0 kcal mol?1. The species are persistent in solution (half‐life≈14–21 h) and in the solid state they are stable for weeks. 相似文献
83.
Dr. Philipp Biegger Olena Tverskoy Dr. Frank Rominger Prof. Dr. Uwe H. F. Bunz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16315-16322
We describe the synthesis and characterization of novel iptycene‐substituted azaacenes by using either a classic condensation route (diamine plus ortho‐quinone) and/or a Pd‐catalyzed coupling of an aromatic diamine with an aromatic dihalide. The attachment of an iptycene unit leads to a significant blueshift (15 nm) in the UV/Vis spectra of these azaacenes. The iptycene unit stabilizes a hexaazahexacene with a λmax abs of 833 nm. By employing 5,6‐diamino(benzothiadiazole) as a synthon for tetraaminobenzene, we could prepare the symmetrical bis‐triptycene‐substituted tetraazapentacene in high yields. 相似文献
84.
Kostas Karikis Evangelos Georgilis Georgios Charalambidis Athanasia Petrou Dr. Olena Vakuliuk Theodore Chatziioannou Iliana Raptaki Sofia Tsovola Ioanna Papakyriacou Prof. Anna Mitraki Prof. Daniel T. Gryko Prof. Athanassios G. Coutsolelos 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(32):11245-11252
A series of conjugates of amino acids with porphyrins and corroles was synthesized. Their self‐assembling ability under defined conditions was investigated by scanning electron microscopy. The morphology and photophysical properties of these molecules were studied by absorption and fluorescence spectroscopy in solid, liquid, and self‐assembled forms. We observed that both corrole and porphyrin conjugated with the l ‐phenylalanine–l ‐phenylalanine peptide to form spherical nanostructures with bathochromic shifts in the emission spectra, indicating the formation of aggregates. These aggregates are characterized by the impressive absorption of light over nearly the whole visible range. The broadening of all bands was particularly strong in the case of corroles. The fluorescence lifetimes of self‐assembled species were longer as compared to the solid‐state form. 相似文献
85.
Influence of the Synthetic Conditions on the Structural and Electrochemical Properties of Carbon Nano‐Onions 下载免费PDF全文
Olena Mykhailiv Dr. Andrzej Lapinski Dr. Agustin Molina‐Ontoria Elzbieta Regulska Prof. Dr. Luis Echegoyen Dr. Alina T. Dubis Dr. Marta E. Plonska‐Brzezinska 《Chemphyschem》2015,16(10):2182-2191
Thermal annealing of nanodiamonds with diameters of a few nanometers (in an inert atmosphere and at temperatures in the range: 1500–1800 °C) leads to the formation of carbon nano‐onions (CNOs) with diameters between 5 and 6 nm, which correspond to nanostructures with six to eight graphitic layers. The resulting spherical CNO structures were thermally modified under different atmospheres and characterized by SEM, TEM, thermogravimetric analysis and spectroscopic (Raman and diffuse reflectance infrared Fourier transform/FTIR) spectroscopy. The electrochemical properties of the CNOs prepared under different conditions were determined and compared. The results reveal that the CNOs show different structures with predominant spherical “small” carbon nano‐onions. The aim of this article is to investigate the impact of the CNO′s synthesis conditions on the resulting structures and study the effect of further thermal modifications on the sizes, shapes and homogeneity of these carbon nanostructures. 相似文献
86.
Mechanistic Aspects of Aryl–Halide Oxidative Addition,Coordination Chemistry,and Ring‐Walking by Palladium 下载免费PDF全文
Prof. Olena V. Zenkina Dr. Ori Gidron Dr. Linda J. W. Shimon Dr. Mark A. Iron Prof. Milko E. van der Boom 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):16113-16125
This contribution describes the reactivity of a zero‐valent palladium phosphine complex with substrates that contain both an aryl halide moiety and an unsaturated carbon–carbon bond. Although η2‐coordination of the metal center to a C?C or C?C unit is kinetically favored, aryl halide bond activation is favored thermodynamically. These quantitative transformations proceed under mild reaction conditions in solution or in the solid state. Kinetic measurements indicate that formation of η2‐coordination complexes are not nonproductive side‐equilibria, but observable (and in several cases even isolated) intermediates en route to aryl halide bond cleavage. At the same time, DFT calculations show that the reaction with palladium may proceed through a dissociation–oxidative addition mechanism rather than through a haptotropic intramolecular process (i.e., ring walking). Furthermore, the transition state involves coordination of a third phosphine to the palladium center, which is lost during the oxidative addition as the C?halide bond is being broken. Interestingly, selective activation of aryl halides has been demonstrated by adding reactive aryl halides to the η2‐coordination complexes. The product distribution can be controlled by the concentration of the reactants and/or the presence of excess phosphine. 相似文献
87.
88.
Olena Naboka 《Journal of Mathematical Analysis and Applications》2008,341(2):1107-1124
The dynamical system arising in the study of nonlinear oscillations of a number of coupled Berger plates is considered. The dependence of the long-time behavior of the trajectories of the system on the properties of the coupling operator is studied. It is shown that the global attractor of the dynamical system is continuous with respect to the coupling parameter γ expressing the intensity of plate interaction. When γ→∞ it converges upper semicontinuously to the attractor of the system generated by the projection of the vector field of the coupled system on the kernel of the coupling operator. For the particular case of 3-diagonal coupling operator the synchronization phenomenon at the level of attractors is stated for large values of γ as well as the absence of synchronization for γ small. The case of cluster synchronization is also considered. 相似文献
89.
Gaurav Singh David Sier Andreas T. Ernst Olena Gavriliouk Rob Oyston Tracey Giles Palitha Welgama 《European Journal of Operational Research》2012
The Hunter Valley Coal Chain is the largest coal export operation in the world with a throughput in excess of 100 million tonnes per annum (Mtpa). Coal is delivered to the shipping terminal from 40 mines using 27 coal load points spread across the Hunter Valley region. This paper describes an MILP model for determining the capacity requirements, and the most cost effective capacity improvement initiatives, to meet demand while minimising the total cost of infrastructure and demurrage. We present results from computational experiments on the model’s performance along with a comparison of the model’s output with detailed analyses by the coal chain analysts and planners. 相似文献
90.
Olena Magda 《Communications in Nonlinear Science & Numerical Simulation》2012,17(12):5288-5290
It is shown that in the commented paper the exact solutions were found only for those variable-coefficient KdV equations which are reduced to the classical (constant-coefficient) KdV equation by point transformations, and these solutions are preimages of well-known traveling wave solutions of the KdV equation with respect to the corresponding point transformations. The equivalence-based approach suggested in [Popovych RO, Vaneeva OO. More common errors in finding exact solutions of nonlinear differential equations: Part I. Commun Nonlinear Sci Numer Simul 2010;15:3887–99] allows one to obtain more results. This disproves the relevance of the extended mapping transformation method for the class of equations under consideration. 相似文献