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151.
How Does Peripheral Functionalization of Ruthenium(II)–Terpyridine Complexes Affect Spatial Charge Redistribution after Photoexcitation at the Franck–Condon Point?
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Julia Preiß Dr. Michael Jäger Prof. Dr. Sven Rau Prof. Dr. Benjamin Dietzek Prof. Dr. Jürgen Popp Prof. Dr. Todd Martínez Dr. Martin Presselt 《Chemphyschem》2015,16(7):1395-1404
Ruthenium polypyridine‐type complexes are extensively used sensitizers to convert solar energy into chemical and/or electrical energy, and they can be tailored through their metal‐to‐ligand charge‐transfer (MLCT) properties. Much work has been directed at harnessing the triplet MLCT state in photoinduced processes, from sophisticated molecular architectures to dye‐sensitized solar cells. In dye‐sensitized solar cells, strong coupling to the semiconductor exploits the high reactivity of the (hot) singlet/triplet MLCT state. In this work, we explore the nature of the 1MLCT states of remotely substituted RuII model complexes by both experimental and theoretical techniques. Two model complexes with electron‐withdrawing (i.e. NO2) and electron‐donating (i.e. NH2) groups were synthesized; these complexes contained a phenylene spacer to serve as a spectroscopic handle and to confirm the contribution of the remote substituent to the 1MLCT transition. [Ru(tpy)2]2+‐based complexes (tpy=2,2′:6′,2′′‐terpyridine) were further desymmetrized by tert‐butyl groups to yield unidirectional 1MLCTs with large transition dipole moments, which are beneficial for related directional charge‐transfer processes. Detailed comparison of experimental spectra (deconvoluted UV/Vis and resonance Raman spectroscopy data) with theoretical calculations based on density functional theory (including vibronic broadening) revealed different properties of the optically active bright 1MLCT states already at the Franck–Condon point. 相似文献
152.
M. Sc. Yasemin Akbulut Hannah J. Gaunt Prof. Katsuhiko Muraki Dr. Melanie J. Ludlow Dr. Mohamed S. Amer Dr. Alexander Bruns Dr. Naveen S. Vasudev Dr. Lea Radtke Dr. Matthieu Willot M. Sc. Sven Hahn M. Sc. Tobias Seitz Dr. Slava Ziegler Prof. Dr. Mathias Christmann Prof. Dr. David J. Beech Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2015,54(12):3787-3791
Current therapies for common types of cancer such as renal cell cancer are often ineffective and unspecific, and novel pharmacological targets and approaches are in high demand. Here we show the unexpected possibility for the rapid and selective killing of renal cancer cells through activation of calcium‐permeable nonselective transient receptor potential canonical (TRPC) calcium channels by the sesquiterpene (?)‐englerin A. This compound was found to be a highly efficient, fast‐acting, potent, selective, and direct stimulator of TRPC4 and TRPC5 channels. TRPC4/5 activation through a high‐affinity extracellular (?)‐englerin A binding site may open up novel opportunities for drug discovery aimed at renal cancer. 相似文献
153.
A Separation‐Integrated Cascade Reaction to Overcome Thermodynamic Limitations in Rare‐Sugar Synthesis
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Nina Wagner Andreas Bosshart Jurek Failmezger Dr. Matthias Bechtold Prof. Sven Panke 《Angewandte Chemie (International ed. in English)》2015,54(14):4182-4186
Enzyme cascades combining epimerization and isomerization steps offer an attractive route for the generic production of rare sugars starting from accessible bulk sugars but suffer from the unfavorable position of the thermodynamic equilibrium, thus reducing the yield and requiring complex work‐up procedures to separate pure product from the reaction mixture. Presented herein is the integration of a multienzyme cascade reaction with continuous chromatography, realized as simulated moving bed chromatography, to overcome the intrinsic yield limitation. Efficient production of D ‐psicose from sucrose in a three‐step cascade reaction using invertase, D ‐xylose isomerase, and D ‐tagatose epimerase, via the intermediates D ‐glucose and D ‐fructose, is described. This set‐up allowed the production of pure psicose (99.9 %) with very high yields (89 %) and high enzyme efficiency (300 g of D ‐psicose per g of enzyme). 相似文献
154.
Sven Heiles Richard J. Cooper Matthew J. DiTucci Evan R. Williams 《Chemical science》2015,6(6):3420-3429
Hydration of gaseous guanidinium (Gdm+) with up to 100 water molecules attached was investigated using infrared photodissociation spectroscopy in the hydrogen stretch region between 2900 and 3800 cm–1. Comparisons to IR spectra of low-energy computed structures indicate that at small cluster size, water interacts strongly with Gdm+ with three inner shell water molecules each accepting two hydrogen bonds from adjacent NH2 groups in Gdm+. Comparisons to results for tetramethylammonium (TMA+) and Na+ enable structural information for larger clusters to be obtained. The similarity in the bonded OH region for Gdm(H2O)20
+
vs. Gdm(H2O)100
+ and the similarity in the bonded OH regions between Gdm+ and TMA+ but not Na+ for clusters with <50 water molecules indicate that Gdm+ does not significantly affect the hydrogen-bonding network of water molecules at large size. These results indicate that the hydration around Gdm+ changes for clusters with more than about eight water molecules to one in which inner shell water molecules only accept a single H-bond from Gdm+. More effective H-bonding drives this change in inner-shell water molecule binding to other water molecules. These results show that hydration of Gdm+ depends on its local environment, and that Gdm+ will interact with water even more strongly in an environment where water is partially excluded, such as the surface of a protein. This enhanced hydration in a limited solvation environment may provide new insights into the effectiveness of Gdm+ as a protein denaturant. 相似文献
155.
Improved Spectral Coverage and Fluorescence Quenching in Donor–acceptor Systems Involving Indolo[3‐2‐b]carbazole and Boron‐dipyrromethene or Diketopyrrolopyrrole
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Adis Khetubol Sven Van Snick Melissa L. Clark Eduard Fron Eduardo Coutiño‐González Arvid Cloet Koen Kennes Yuliar Firdaus Maarten Vlasselaer Volker Leen Wim Dehaen Mark Van der Auweraer 《Photochemistry and photobiology》2015,91(3):637-653
A novel π‐conjugated triad and a polymer incorporating indolo[3,2‐b]‐carbazole (ICZ) and 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) were synthesized via a Sonogashira coupling. Compared to the parent BODIPY the absorption and fluorescence spectrum were for both compounds broader and redshifted. The redshift of the fluorescence and the decrease of the fluorescence quantum yield and decay time upon increasing solvent polarity were attributed to the formation of a partial charge‐transfer state. Upon excitation in the ICZ absorption band the ICZ fluorescence was quenched in both compounds mainly due to energy transfer to the BODIPY moiety. In a similar ICZ–π–DPP polymer (where DPP is diketopyrrolopyrrole), a smaller redshift of the absorption and fluorescence spectra compared to the parent DPP was observed. A less efficient quenching of the ICZ fluorescence in the ICZ–π–DPP polymer could be related to the unfavorable orientation of the transition dipoles of ICZ and DPP. The rate constant for energy transfer was for all compounds an order of magnitude smaller than predicted by Förster theory. While in a solid film of the triad a further redshift of the absorption maximum of nearly 100 nm was observed, no such shift was observed for the ICZ–π–BODIPY polymer. 相似文献
156.
157.
158.
Dr. Natalie Spomer Dr. Sven Holl Dr. Larissa Zherlitsyna Dr. Fariba Maysamy Andreas Frost Prof. Dr. Norbert Auner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5600-5616
Amorphous silicon is synthesized by treating the tetrahalosilanes SiX4 (X=Cl, F) with molten sodium in high boiling polar and non‐polar solvents such as diglyme or nonane to give a brown or a black solid showing different reactivities towards suitable reagents. With regards to their technical relevance, their stability towards oxygen, air, moisture, chlorine‐containing reaction partners RCl (R=H, Cl, Me) and alcohols is investigated. In particular, reactions with methanol are a versatile tool to deliver important products. Besides tetramethoxysilane formation, methanolysis of silicon releases hydrogen gas under ambient conditions and is thus suitable for a decentralized hydrogen production; competitive insertion into the MeO?H versus the Me?OH bond either yields H‐ and/or methyl‐substituted methoxy functional silanes. Moreover, compounds, such as MenSi(OMe)4?n (n=0–3) are simply accessible in more than 75 % yield from thermolysis of, for example, tetramethoxysilane over molten sodium. Based on our systematic investigations we identified reaction conditions to produce the methoxysilanes MenSi(OMe)4?n in excellent (n=0:100 %) to acceptable yields (n=1:51 %; n=2:27 %); the yield of HSi(OMe)3 is about 85 %. Thus, the methoxysilanes formed might possibly open the door for future routes to silicon‐based products. 相似文献
159.
160.
We prove a Desch‐Schappacher type perturbation theorem for strongly continuous and locally equicontinuous one‐parameter semigroups which are defined on a sequentially complete locally convex space. 相似文献