排序方式: 共有14条查询结果,搜索用时 187 毫秒
1.
Dr. Chavdar Slavov Dr. Chong Yang Andreas H. Heindl Prof. Hermann A. Wegner Prof. Andreas Dreuw Prof. Josef Wachtveitl 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):388-395
Azoheteroarene photoswitches have attracted attention due to their unique properties. We present the stationary photochromism and ultrafast photoisomerization mechanism of thiophenylazobenzene (TphAB). It demonstrates impressive fatigue resistance and photoisomerization efficiency, and shows favorably separated (E)- and (Z)-isomer absorption bands, allowing for highly selective photoconversion. The (Z)-isomer of TphAB adopts an unusual orthogonal geometry where the thiophenyl group is perfectly perpendicular to the phenyl group. This geometry is stabilized by a rare lone-pair⋅⋅⋅π interaction between the S atom and the phenyl group. The photoisomerization of TphAB occurs on the sub-ps to ps timescale and is governed by this interaction. Therefore, the adoption and disruption of the orthogonal geometry requires significant movement along the inversion reaction coordinates (CNN and NNC angles). Our results establish TphAB as an excellent photoswitch with versatile properties that expand the application possibilities of AB derivatives. 相似文献
2.
Todorov Vladislav T. Dutsov Chavdar Ch. Cassette Philippe Mitev Krasimir K. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3249-3258
Journal of Radioanalytical and Nuclear Chemistry - This work shows a study of the effect of the non-uniformity of photocathode response on the energy resolution of plastic scintillators optimized... 相似文献
3.
Chavdar Slavov Chong Yang Andreas H. Heindl Hermann A. Wegner Andreas Dreuw Josef Wachtveitl 《Angewandte Chemie (International ed. in English)》2020,59(1):380-387
Azoheteroarene photoswitches have attracted attention due to their unique properties. We present the stationary photochromism and ultrafast photoisomerization mechanism of thiophenylazobenzene (TphAB). It demonstrates impressive fatigue resistance and photoisomerization efficiency, and shows favorably separated (E)‐ and (Z)‐isomer absorption bands, allowing for highly selective photoconversion. The (Z)‐isomer of TphAB adopts an unusual orthogonal geometry where the thiophenyl group is perfectly perpendicular to the phenyl group. This geometry is stabilized by a rare lone‐pair???π interaction between the S atom and the phenyl group. The photoisomerization of TphAB occurs on the sub‐ps to ps timescale and is governed by this interaction. Therefore, the adoption and disruption of the orthogonal geometry requires significant movement along the inversion reaction coordinates (CNN and NNC angles). Our results establish TphAB as an excellent photoswitch with versatile properties that expand the application possibilities of AB derivatives. 相似文献
4.
Julie Thevarpadam Irene Bessi Oliver Binas Dr. Diana P. N. Gonçalves Dr. Chavdar Slavov Dr. Hendrik R. A. Jonker Dr. Christian Richter Prof. Dr. Josef Wachtveitl Prof. Dr. Harald Schwalbe Prof. Dr. Alexander Heckel 《Angewandte Chemie (International ed. in English)》2016,55(8):2738-2742
The ability of three different bifunctional azobenzene linkers to enable the photoreversible formation of a defined intermolecular two‐tetrad G‐quadruplex upon UV/Vis irradiation was investigated. Circular dichroism and NMR spectroscopic data showed the formation of G‐quadruplexes with K+ ions at room temperature in all three cases with the corresponding azobenzene linker in an E conformation. However, only the para–para‐substituted azobenzene derivative enables photoswitching between a nonpolymorphic, stacked, tetramolecular G‐quadruplex and an unstructured state after E–Z isomerization. 相似文献
5.
Eduard Pelay Alex Tarancón Krasimir Mitev Chavdar Dutsov Strahil Georgiev Ludmil Tsankov José Francisco García 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(2):637-649
Several studies have demonstrated that polycarbonate-based polymers have good capacities for the absorption of 222Rn. Meanwhile, polystyrene polymers are reported to be the most appropriate for developing plastic scintillator materials for the detection of radioactivity. The objective of this work was to develop plastic scintillators in the form of microspheres (PSm) composed of polystyrene and polycarbonate that could be used to measure 222Rn and improve this performance thanks to the combination of characteristics of both polymers. Our results show that PSm of polystyrene and polycarbonate can be made via the evaporation/extraction method, despite the two polymers not being miscible. From the point of view of the radioactive measurements, we observed that the addition of polycarbonate causes quenching, although it does not significantly affect the detection efficiency for alpha and high-energy beta emitters. From the point of view of 222Rn absorption, we observed that synthesis of the PSm through the evaporation/extraction method changes the 222Rn absorption of the raw material. This result demonstrates that the method of production of the polymer and the resulting physical characteristics are a key parameter for its final 222Rn absorption properties. 相似文献
6.
Molybdenum HDS catalysts supported on niobia-silica 总被引:1,自引:0,他引:1
Sonia Damyanova Stanislava Andonova Iskra Stereva Chavdar Vladov Lachezar Petrov Paul Grange 《Reaction Kinetics and Catalysis Letters》2003,79(1):35-42
The effect of the amount of Nb2O5on the dispersion and reductive properties of Mo/Nb2O5-SiO2 catalysts has been studied. Addition of niobium leads to an increase of the dispersion, and the reducibility of molybdenum.
A synergetic effect of niobium on the catalytic activity in hydrodesulfurization of thiophene was observed at 5.4 wt.% of
Nb2O5.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
Chavdar Slavov Madina Mansurova Alfred R. Holzwarth Wolfgang Gärtner 《Photochemistry and photobiology》2010,86(1):31-38
The photochemical reactions of the 1-deaza derivative of riboflavin (RF) have been studied by sub-ps time-resolved fluorescence spectroscopy. A potential effect of the solvent polarity and hydrogen bonding capability on the excited state (ES) dynamics was tested by measuring 1-deaza RF in water and, after acetylation of the sugar moiety, also in acetonitrile. Opposite to former reports, which indicated no fluorescence after laser excitation (Spencer et al. [1977] Biochemistry 16 : 3586–3594), we find a significant fluorescence in either solvent. For both compounds, the fluorescence decays are biexponential with lifetimes in the ps time domain (1.8 and 12.5 ps for 1-deaza RF, and 3 and 87 ps for Ac4 -1-deaza RF). In addition, a third, independent fluorescence decay was observed for both compounds. The remarkably slower second decay process for the measurements of the tetra-acetyl derivative in acetonitrile points to the involvement of hydrogen bonding or changes in the protonation/tautomerization state in the ES. In contrast to the parent compound (RF), no triplet state formation can be detected for 1-deaza RF, making the internal conversion and the fluorescence the only decay processes of the ES. 相似文献
8.
Lucie echov Juraj Filo Martin Dra
ínský Chavdar Slavov Dazhong Sun Zlatko Janeba Tom Slanina Josef Wachtveitl Elika Prochzkov Marek Cig 《Angewandte Chemie (International ed. in English)》2020,59(36):15590-15594
Photochromic systems with an ultrahigh rate of thermal relaxation are highly desirable for the development of new efficient photochromic oscillators. Based on DFT calculations, we designed a series of 5‐phenylazopyrimidines with strong push–pull character in silico and observed very low energy barriers for the thermal (Z)‐to‐(E) isomerization. The structure of the (Z)‐isomer of the slowest isomerizing derivative in the series was confirmed by NMR analysis with in situ irradiation at low temperature. The substituents can tune the lifetime of thermal back isomerization from hundreds of microseconds to several nanoseconds (8 orders of magnitude). The photoswitching parameters were extracted from transient absorption techniques and a dominant rotation mechanism of the (Z)‐to‐(E) thermal fading was proposed based on DFT calculations. 相似文献
9.
10.
Lucie Čechová Dr. Juraj Filo Dr. Martin Dračínský Dr. Chavdar Slavov Dazhong Sun Dr. Zlatko Janeba Dr. Tomáš Slanina Prof. Dr. Josef Wachtveitl Dr. Eliška Procházková Dr. Marek Cigáň 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(36):15720-15724
Photochromic systems with an ultrahigh rate of thermal relaxation are highly desirable for the development of new efficient photochromic oscillators. Based on DFT calculations, we designed a series of 5-phenylazopyrimidines with strong push–pull character in silico and observed very low energy barriers for the thermal (Z)-to-(E) isomerization. The structure of the (Z)-isomer of the slowest isomerizing derivative in the series was confirmed by NMR analysis with in situ irradiation at low temperature. The substituents can tune the lifetime of thermal back isomerization from hundreds of microseconds to several nanoseconds (8 orders of magnitude). The photoswitching parameters were extracted from transient absorption techniques and a dominant rotation mechanism of the (Z)-to-(E) thermal fading was proposed based on DFT calculations. 相似文献