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951.
Margherita BarberoStefano Bazzi Silvano CadamuroLorenzo Di Bari Stefano Dughera Giovanni Ghigo Daniele PadulaSilvia Tabasso 《Tetrahedron》2011,67(32):5789-5797
We have recently reported the use, in catalytic amounts, of 1,2-benzenedisulfonimide as a safe Brønsted acid in some acid-catalyzed organic reactions. With the design of new and chiral acid organocatalysts with the structure of 1,2-benzenedisulfonimide in mind, we herein propose a synthesis of 1,2-benzenedisulfonimide derivatives bearing an aryl group in the 3-position with good overall yields. The chirality of these compounds is due to the hindered rotation of the aryl group (atropisomerism). We resolved the atropisomers of one of these compounds. 相似文献
952.
Massimo Gianotti Daniele AndreottiDavide Casotto Mario MattioliAnna Mingardi Francesca PavoneRoberto Profeta Filippo Valente 《Tetrahedron letters》2011,52(2):329-331
A new synthetic pathway to the final compound 1-[(1S)-5’,11’-dihydrospiro[cyclopentane-1,10’-dibenzo[a,d]cyclohepten]-3-yl]-3-azetidinecarboxylic acid (1) was set up. The two preparative chiral HPLC separations needed in the first route were successfully avoided and replaced by two diastereomeric crystallizations of intermediate compounds 5 and 10. 相似文献
953.
Yildizhan MM Fazzi D Milani A Brambilla L Del Zoppo M Chalifoux WA Tykwinski RR Zerbi G 《The Journal of chemical physics》2011,134(12):124512
The infrared (IR) spectrum of an adamantyl endcapped α, ω-polyyne (the hexayne, Ad-C(12)-Ad) is investigated both experimentally and computationally. A new IR band is observed upon UV photoexcitation of the compound (embedded in a poly methyl methacrylate matrix at 78 K), thus, revealing the existence of new photogenerated molecular structure trapped at low temperature. Complete reversibility is found, thus, demonstrating that the photoexcitation is responsible for the generation of metastable excited states of the molecule. Density functional theory and time dependent density functional theory calculations indicate that these metastable states result from the forbidden singlet (S(1)) or triplet (T(1)) excited states, and geometry optimizations of the polyyne trapped in either S(1) and/or T(1) states demonstrate that the carbon chain takes on a cumulenic structure. Comparison of the experimental and the computed IR spectra for the molecule trapped in the forbidden states confirms that the new IR features are clear markers of cumulenic species. The temperature and time dependent behavior of the new IR band is analyzed, while the experimentally determined value of the activation energy highlights the low stability of these molecular structures. 相似文献
954.
Stöhr M Boz S Schär M Nguyen MT Pignedoli CA Passerone D Schweizer WB Thilgen C Jung TA Diederich F 《Angewandte Chemie (International ed. in English)》2011,50(42):9982-9986
Birds of a feather flock together: STM and DFT studies provide the first example of spontaneous chiral resolution of a helicene on a surface. Racemic 6,13-dicyano[7]helicene forms fully segregated domains of pure enantiomers (2D conglomerate) on Cu(111). The propensity of the system to optimize intermolecular CN???HC(Ar) hydrogen bonding and CN???CN dipolar interactions translates into chiral recognition with preferential assembly of homochiral molecules. 相似文献
955.
956.
957.
Perissinotto S Garbugli M Fazzi D Bertarelli C Carvelli M Kandada AR Yue Z Wong KS Lanzani G 《Chemphyschem》2011,12(18):3619-3623
A novel system for the modulation of amplified emission based on a polyfluorene/diarylethene (namely F8BT/DTP) blend is shown. The high sensitivity of amplified spontaneous emission (ASE) is exploited to achieve efficient emission modulation with a low-intensity control signal. Modulation is then characterized by photoluminescence (PL) lifetime measurements, photocurrent experiments, and density functional theory calculations. This system can also act as a photocurrent switch based on the same principle. This technique may represent a useful tool for fluorescence quenching and sensing as well as find application in organic photonics. 相似文献
958.
Quantum chemical calculations (DFT, TDDFT and ZINDO/S) of singlet and triplet exciton couplings are presented and discussed for some acene derivatives (such as anthracene, tetracene, 9,10-di(phenyl)anthracene and 9,10-bis(phenylethynyl)anthracene). An accurate excited state single molecule characterization has been carried out followed by an analysis of the inter-molecular excitonic interactions, taking place in the crystalline phase. These have been correlated to exciton coupling terms obtaining guidelines for the choice of molecular materials with large exciton couplings. Such organic systems are likely to show multiexciton processes such as singlet fission (SF) and triplet-triplet annihilation (TTA) which are useful in energy conversion phenomena to be exploited in photonic and optoelectronic devices. 相似文献
959.
The synthesis of highly functionalised N-heterocycles has been achieved by the visible light mediated photoredox conversion of tertiary amines to azomethine ylides and their further reaction with maleimide derivatives as dipolarophiles. 相似文献
960.
Daniele Bergamasco Franco Bulian Andrea Melchior Davide Menotti Paolo Tirelli Marilena Tolazzi 《Journal of Thermal Analysis and Calorimetry》2011,103(1):65-68
In previous studies some waterborne coatings, specifically formulated for the scope of the research, were studied during an
artificial weathering process by means of dynamic mechanical analysis (DMA) technique. In those studies the chemical and physical
parameters which mainly affect the performance of coatings and their evolution during weathering were measured. The aim was
to predict the performance of coatings for exterior wood during their service life by means of accelerated artificial tests
and instrumental measures. In this study four commercial products were artificially weathered following the European standard
EN 927-6. The changes in the mechanical properties were measured by means of the DMA as reported in the previous studies.
With this research the authors have verified the capability of this method to predict the performance in use of coatings. 相似文献