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排序方式: 共有235条查询结果,搜索用时 15 毫秒
31.
Magali A. Rodrigues Sérgio Brochsztain Teresa C. Barros Mauricio S. Baptista Mario J. Politi 《Photochemistry and photobiology》1999,70(1):35-39
Abstract— The effect of the protonation state of a novel aqueous soluble N,N'-di(2-phosphonoethyl)-l,4,5,8-naphthalene-diimide (DPN) on its spectroscopic properties is studied. In aqueous solution DPN depicts linear Lambert-Beer plots up to the solubility limits at pH 1.0, 7.1 and 10.1, in accordance with its solubilization as a monomer. A small increase in the extinction coefficients with pH is observed. Conversely a strong decrease in the fluorescence emission yields are observed with the increase in pH. These results are shown to originate from the distinct efficiencies of the intersystem crossing of DPN as a function of the net charge on the phosphono moieties. Accordingly, from the decrease in fluorescence emission, titration curves were obtained resulting in two pKa of –1.5 and 6.7 in agreement with the potentiometric analysis. In parallel monitoring the amount of heat deposited in the system shows an inverse pattern, that is, increase in the thermal tensing time-resolved signal with pH. Laser flash photolysis and thermal Iensing data in the absence and presence of oxygen show the interplay of an intersystem crossing process with the protonation state of the dye. The changes in protonation from neutral to two- and four-fold charged species are accompanied by an enhancing effect on the naphthalenediimide ring toward spin inversion (triplet formation) and consequently in different fluorescence yields 相似文献
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33.
Emilie RipaudCharlotte Mallet Magali AllainPhilippe Leriche Pierre FrèreJean Roncali 《Tetrahedron letters》2011,52(49):6573-6577
Two triphenylamine derivatives bearing terminal perfluorophenyl groups have been synthesized. Their HOMO, LUMO levels and electronic band gap have been evaluated by spectroscopic and electrochemical measurements and rationalized with theoretical calculations. X-ray structure analysis of crystals allowed the observation of multiple intermolecular interactions due to the presence of the perfluorophenyl pendant groups. The multiplication of these interactions explains the differences between calculated (in gas phase) and observed (in solid states) structures. 相似文献
34.
Fehr C Magpantay I Vuagnoux M Dupau P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(4):1257-1260
(E)-Trisubstituted allylic alcohols are commonly prepared from the corresponding (E)-enals, themselves readily accessible by a simple aldol condensation reaction. We demonstrate that these very same (E)-enals can be converted into (Z)-trisubstituted allylic acetates (and thus alcohols) by a ruthenium-catalyzed 1,4-hydrogenation of the corresponding dienol acetates. This simple solution to a long-lasting problem was applied to an industrially feasible synthesis of (-)-β-santalol. 相似文献
35.
Josefina Alvarez Magali Folch-Gabayet Salvador Pérez-Esteva 《Journal of Fourier Analysis and Applications》2001,7(1):49-62
The purpose of this article is to study the Hilbert space W2\mathcal{ W}^2 consisting of all solutions of the Helmholtz equation Du+u=0\Delta u+u=0 in
\BbbR2\Bbb{R}^2 that are the image under the Fourier transform of L2L^2 densities in the unit circle. We characterize this space as a close subspace of the Hilbert space H2\mathcal{ H}^2 of all functions belonging to L2( | x | -3dx) L^2( | x | ^{-3}dx) jointly with their angular and radial derivatives, in the complement of the unit disk in
\BbbR2\Bbb{R}^2. We calculate the reproducing kernel of W2\mathcal{ W}^2 and study its reproducing properties in the corresponding spaces Hp\mathcal{H}^p, for $p>1$p>1. 相似文献
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37.
Lyskawa J Sallé M Balandier JY Le Derf F Levillain E Allain M Viel P Palacin S 《Chemical communications (Cambridge, England)》2006,(21):2233-2235
The formation of the two dimeric species [(TTF)2]+* and (TTF+*)2 can be monitored by complexation of Na+ on a calix[4]arene-TTF assembly. 相似文献
38.
Rational Topological Design for Fluorescence Enhancement upon Aggregation of Distyrylfuran Derivatives 下载免费PDF全文
Dr. Charlotte Mallet Dr. Chady Moussallem Alexandre Faurie Magali Allain Dr. Frédéric Gohier Prof. William G. Skene Prof. Pierre Frère 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(21):7944-7953
A series of 2,5‐distyrylfuran derivatives bearing pentafluorophenyl‐ and cyanovinyl units have been synthesized for aggregation‐induced emission (AIE). The effect of the type and extent of the supramolecular connections on the AIE of the furan derivatives were examined and correlated with their X‐ray crystal structures. It was found that the simultaneous presence of cyano and perfluorophenyl units strongly enhances the fluorescence upon aggregation. Single‐crystal X‐ray diffraction analysis confirmed that C?H???F, F???F, C?H???nitrile, Ar???ArF (Ar=aryl, ArF=fluoroaryl), and nitrile???ArF intra‐ and intermolecular interactions drive the topology of the molecule and that solid‐state supramolecular contacts favor AIE of the furan derivatives. 相似文献
39.
Alías S Andreu R Blesa MJ Cerdán MA Franco S Garín J López C Orduna J Sanz J Alicante R Villacampa B Allain M 《The Journal of organic chemistry》2008,73(15):5890-5898
A short, high-yielding route to omega-dithiafulvenylpolyenals (1) via the corresponding iminium salts (2) and starting from trimethyl-1,3-dithiolium tetrafluoroborate is reported. The Knoevenagel reactions of either 1 or 2 with isoxazolone-containing acceptors afford merocyanines 7 and 9, in a process that is often accompanied by a vinylene-shortening side reaction. Experimental and theoretical studies reveal that compounds 7 and 9, featuring two proaromatic end groups, are strongly polarized and show good second-order nonlinear optical responses. 相似文献
40.
Duvail M Souaille M Spezia R Cartailler T Vitorge P 《The Journal of chemical physics》2007,127(3):034503
Pair interaction potentials (IPs) were defined to describe the La(3+)-OH(2) interaction for simulating the La(3+) hydration in aqueous solution. La(3+)-OH(2) IPs are taken from the literature or parametrized essentially to reproduce ab initio calculations at the second-order Moller-Plesset level of theory on La(H(2)O)(8) (3+). The IPs are compared and used with molecular dynamics (MD) including explicit polarization, periodic boundary conditions of La(H(2)O)(216) (3+) boxes, and TIP3P water model modified to include explicit polarization. As expected, explicit polarization is crucial for obtaining both correct La-O distances (r(La-O)) and La(3+) coordination number (CN). Including polarization also modifies hydration structure up to the second hydration shell and decreases the number of water exchanges between the La(3+) first and second hydration shells. r(La-O) ((1))=2.52 A and CN((1))=9.02 are obtained here for our best potential. These values are in good agreement with experimental data. The tested La-O IPs appear to essentially account for the La-O short distance repulsion. As a consequence, we propose that most of the multibody effects are correctly described by the explicit polarization contributions even in the first La(3+) hydration shell. The MD simulation results are slightly improved by adding a-typically negative 1r(6)-slightly attractive contribution to the-typically exponential-repulsive term of the La-O IP. Mean residence times are obtained from MD simulations for a water molecule in the first (1082 ps) and second (7.6 ps) hydration shells of La(3+). The corresponding water exchange is a concerted mechanism: a water molecule leaving La(H(2)O)(9) (3+) in the opposite direction to the incoming water molecule. La(H(2)O)(9) (3+) has a slightly distorded "6+3" tricapped trigonal prism D(3h) structure, and the weakest bonding is in the medium triangle, where water exchanges take place. 相似文献