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81.
Delphine Felder Manuel GutirrezNava Maria delPilarCarren Jean‐Franois Eckert Michaël Luccisano Corinne Schall Patrick Masson Jean‐Louis Gallani Benoît Heinrich Daniel Guillon Jean‐Franois Nierengarten 《Helvetica chimica acta》2002,85(1):288-319
Various amphiphilic fullerene derivatives were prepared by functionalization of [5,6]fullerene‐C60‐Ih (C60) with malonate or bis‐malonate derivatives obtained by esterification of the malonic acid mono‐esters 5 – 7 . Cyclopropafullerene 10 was obtained by protection of the carboxylic acid function of 6 as a tert‐butyl ester, followed by Bingel addition to C60 and a deprotection step (Scheme 2). The preparation of 10 was also attempted directly from the malonic acid mono‐ester 6 under Bingel conditions. Surprisingly, the corresponding 3′‐iodo‐3′H‐cyclopropa[1,9][5,6]fullerene‐C60‐Ih‐3′‐carboxylate 11 was formed instead of 10 (Scheme 3). The general character of this new reaction was confirmed by the preparation of 15 and 16 from the malonic acid mono‐esters 13 and 14 , respectively (Scheme 4). All the other amphiphilic fullerene derivatives were prepared by taking advantage of the versatile regioselective reaction developed by Diederich and co‐workers which led to macrocyclic bis‐adducts of C60 by a cyclization reaction at the C‐sphere with bis‐malonate derivatives in a double Bingel cyclopropanation. The bis‐adducts 37 – 39 with a carboxylic acid polar head group and four pendant long alkyl chains of different length were prepared from diol 22 and acids 5 – 7 , respectively (Scheme 9). In addition, the amphiphilic fullerene derivatives 45, 46, 49, 54 , and 55 bearing different polar head groups and compound 19 with no polar head group were synthesized (Schemes 11–13, 15, and 5, resp.). The ability of all these compounds to form Langmuir monolayers at the air‐water interface was investigated in a systematic study. The films at the water surface were characterized by their surface pressure vs. molecular area isotherms, compression and expansion cycles, and Brewster‐angle microscopy. The spreading behavior of compound 10 was not good, the two long alkyl chains in 10 being insufficient to prevent aggregation resulting from the strong fullerene‐fullerene interactions. While no films could be obtained from compound 19 with no polar head group, all the corresponding amphiphilic fullerene bis‐adducts showed good spreading characteristics and reversible behavior upon successive compression/expansion cycles. The encapsulation of the fullerene in a cyclic addend surrounded by four long alkyl chains is, therefore, an efficient strategy to prevent the irreversible aggregation resulting from strong fullerene‐fullerene interactions usually observed for amphiphilic C60 derivatives at the air‐water interface. The balance of hydrophobicity to hydrophilicity was modulated by changing the length of the surrounding alkyl chains or the nature of the polar head group. The best results in terms of film formation and stability were obtained with the compounds having the largest polar head group, i.e. 45 and 46 , and dodecyl chains. Finally, the Langmuir films obtained from the amphiphilic fullerene bis‐adducts were transferred onto solid substrates, yielding high‐quality Langmuir‐Blodgett films. 相似文献
82.
Aline Salvi Corinne Brühlmann Eugenia Migliavacca Pierre‐Alain Carrupt Kurt Hostettmann Bernard Testa 《Helvetica chimica acta》2002,85(3):867-881
In this work, a convenient test of antioxidant activity was developed, with BChE‐contaminated HSA as the target of AAPH‐induced oxidation and its esterase activity as the marker of protein integrity or degradation. The method is relatively simple, of low cost, and convenient to use. Its application to natural polyphenols showed that quercetin ( 1 ), verbascoside ( 2 ), chlorogenic acid ( 3 ), caffeic acid ( 4 ), 1,3,6,7‐tetrahydroxyxanthone ( 5 ), and mangiferin ( 6 ), are good antioxidants (IC50<9 μM ). 1,5‐Dihydroxy‐3‐methoxyxanthone ( 7 ), flemichin D ( 8 ), and cordigone ( 9 ) showed modest activities (ca. 50 μM <IC50<350 μM ), whereas danthrone ( 10 ) was inactive. Complementary experiments with two of the more active antioxidants, namely quercetin ( 1 ) and chlorogenic acid ( 3 ) showed that both antioxidants were better radical scavengers than chain‐breaking antioxidants. The relative adiabatic oxidation potential (ΔHox), the relative H‐bond dissociation energy (ΔHabs), and the first oxidation potential measured by cyclic voltammetry were found to be related to the radical‐scavenging activity of these antioxidants. 相似文献
83.
Romain Siegrist Corinne Baumgartner Paul Seiler Franois Diederich 《Helvetica chimica acta》2005,88(8):2250-2261
We report a short synthetic route that provides optically active 2‐substituted hexahydro‐1H‐pyrrolizin‐3‐ones in four steps from commercially available Boc (tert‐but(oxy)carbonyl))‐protected proline. Diastereoisomers (−)‐ 11 and (−)‐ 12 were assembled from the proline‐derived aldehyde (−)‐ 8 and ylide 9 via a Wittig reaction and subsequent catalytic hydrogenation (Scheme 3). Cleavage of the Boc protecting group under acidic conditions, followed by intramolecular cyclization, afforded the desired hexahydro‐1H‐pyrrolizinones (−)‐ 1 and (+)‐ 13 . Applying the same protocol to ylide 19 afforded hexahydro‐1H‐pyrrolizinones (−)‐ 25 and (−)‐ 26 (Scheme 5). The absolute configuration of the target compounds was determined by a combination of NMR studies (Figs. 1 and 2) and X‐ray crystallographic analysis (Fig. 3). 相似文献
84.
Brian B. Frank Berta Camafort Blanco Samuel Jakob Fiammetta Ferroni Silvia Pieraccini Dr. Alberta Ferrarini Prof. Dr. Corinne Boudon Prof. Dr. Jean‐Paul Gisselbrecht Dr. Paul Seiler Gian Piero Spada Prof. Dr. François Diederich Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9005-9016
Axially chiral, N‐arylated 3,5‐dihydro‐4H‐dinaphtho[2,1‐c:1′,2′‐e]azepines have been prepared by short synthetic protocols from enantiopure 1,1′‐bi(2,2′‐naphthol) (BINOL) and anilines. Alkynes substituted with two N‐phenyldinaphthazepine donors readily undergo a formal [2+2] cycloaddition, followed by retro‐electrocyclization, with tetracyanoethene (TCNE) to yield donor‐substituted 1,1,4,4‐tetracyanobuta‐1,3‐dienes (TCBDs) featuring intense intramolecular charge‐transfer (CT) interactions. A dicyanovinyl derivative substituted with one N‐phenyldinaphthazepine donor was obtained by a “one‐pot” oxidation/Knoevenagel condensation from the corresponding propargylic alcohol. Comparative electrochemical, X‐ray crystallographic, and UV/Vis studies show that the electron‐donor qualities of N‐phenyldinaphthazepine are similar to those of N,N‐dimethylanilino residues. The circular dichroism (CD) spectrum of a push–pull chromophore incorporating the chiral donor moiety features Cotton effects of exceptional intensity. With their elongated shape and the rigidity of the chiral N‐aryldinaphthazepine donors, these chromophores are effective inducers of twist distortion in nematic liquid crystals (LCs). Thus, a series of the dinaphthazepine derivatives was used as dopants in the nematic LC E7 (Merck) and high helical twisting powers (β) of the order of hundreds of μm?1 were measured. Theoretical calculations were employed to elucidate the relation between the structure of the dopants and their helical twisting power. For the derivatives with two dinaphthazepine moieties, a strong dependence of the β‐values on the structure and conformation of the linker between them was found. 相似文献
85.
Anaïs Geny Dr. Nicolas Agenet Dr. Laura Iannazzo Max Malacria Prof. Dr. Corinne Aubert Dr. Vincent Gandon Dr. 《Angewandte Chemie (International ed. in English)》2009,48(10):1810-1813
Cobalt cyclopentadienyl complexes incorporating a fumarate and a CO ligand (see picture) efficiently catalyze inter‐ and intramolecular [2+2+2] cycloadditions of alkynes, nitriles, and/or alkenes to give benzenes, pyridines, or 1,3‐cyclohexadienes. Unlike catalysts such as [CpCo(CO)2] or [CpCo(C2H4)2] (Cp=C5H5), they are air‐stable, easy to handle, compatible with microwave conditions, and do not necessarily require irradiation to be active.
86.
Corinne Coen 《Computational & Mathematical Organization Theory》2009,15(1):19-25
The contrast effect is a psychological phenomenon in which people exaggerate their differences. When making social comparisons,
people cope with the discomforts associated with negative comparisons by criticizing others and splitting into smaller groups
of similar others or by assimilation, depending on whether they perceive themselves as the member of a majority or minority
group, respectively. This contrast or assimilation phenomena can explain the exaggeration of differences among computational
simulation scholars. Those exaggerations are discussed in this paper as well as some realistic reasons for differences. Recognition
of our status as minority group members and the virtues of assimilation and mutual support are advocated.
相似文献
Corinne CoenEmail: |
87.
Krossing I Slattery JM Daguenet C Dyson PJ Oleinikova A Weingärtner H 《Journal of the American Chemical Society》2006,128(41):13427-13434
We have developed a simple and quantitative explanation for the relatively low melting temperatures of ionic liquids (ILs). The basic concept was to assess the Gibbs free energy of fusion (Delta(fus)G) for the process IL(s) --> IL(l), which relates to the melting point of the IL. This was done using a suitable Born-Fajans-Haber cycle that was closed by the lattice (i.e., IL(s) --> IL(g)) Gibbs energy and the solvation (i.e., IL(g) --> IL(l)) Gibbs energies of the constituent ions in the molten salt. As part of this project we synthesized and determined accurate melting points (by DSC) and dielectric constants (by dielectric spectroscopy) for 14 ionic liquids based on four common anions and nine common cations. Lattice free energies (Delta(latt)G) were estimated using a combination of Volume Based Thermodynamics (VBT) and quantum chemical calculations. Free energies of solvation (Delta(solv)G) of each ion in the bulk molten salt were calculated using the COSMO solvation model and the experimental dielectric constants. Under standard ambient conditions (298.15 K and 10(5) Pa) Delta(fus)G degrees was found to be negative for all the ILs studied, as expected for liquid samples. Thus, these ILs are liquid under standard ambient conditions because the liquid state is thermodynamically favorable, due to the large size and conformational flexibility of the ions involved, which leads to small lattice enthalpies and large entropy changes that favor melting. This model can be used to predict the melting temperatures and dielectric constants of ILs with good accuracy. A comparison of the predicted vs experimental melting points for nine of the ILs (excluding those where no melting transition was observed and two outliers that were not well described by the model) gave a standard error of the estimate (s(est)) of 8 degrees C. A similar comparison for dielectric constant predictions gave s(est) as 2.5 units. Thus, from very little experimental and computational data it is possible to predict fundamental properties such as melting points and dielectric constants of ionic liquids. 相似文献
88.
Ortica F Smimmo P Mazzucato U Favaro G Heynderickx A Moustrou C Samat A 《Photochemistry and photobiology》2006,82(5):1326-1333
The photobehavior of five photochromic dipyrrolyl-perfluoro-cyclopentenes was studied by steady state and time-resolved absorption spectroscopy. The quantum yields of the UV-photoinduced ring-closing reaction (coloration) and the visible-stimulated cycloreversion reaction (bleaching) were measured. Kinetic and thermodynamic parameters of thermal bleaching were also determined. Nanosecond time-resolved experiments showed formation of a transient, which was not a precursor of the reaction photoproduct. This transient was tentatively assigned to a radical cation formed by direct photoionization through a short-lived triplet state. The nature of the transient species was supported by photoinduced electron transfer to electron acceptors. 相似文献
89.
Pognon G Boudon C Schenk KJ Bonin M Bach B Weiss J 《Journal of the American Chemical Society》2006,128(11):3488-3489
A new type of very compact Pacman bis-porphyrin scaffold has been obtained in which a calix[4]arene spacer provides both cofacial preorganization and flexibility. Changes in the distance between the two tetrapyrrolic macrocycles can be triggered by electrochemistry, where closed and open conformers can be interconverted in a handclapping motion. 相似文献
90.
Valérie Samouillan Edouard Lamy Jany Dandurand Alexandrine Foucault-Bertaud Corinne Chareyre Colette Lacabanne Philippe Charpiot 《Journal of Non》2009,355(14-15):830-835
The thermal and dielectric properties of the elastin network were investigated in arteries cultured with physiological and pathological concentrations of homocysteine, an aminoacid responsible of histological impairments in human arteries. The glass transition of this amorphous protein was investigated by Differential Scanning Calorimetry (DSC). To explore the molecular dynamics of the elastin network in the nanometer range, we used Thermally Stimulated Currents (TSC), a dielectric technique running at low frequency and measuring the dipolar reorientations in proteins subjected to a static electrical field. Combining TSC and DSC experiments with determination of the activation parameters of relaxation times reveals the molecular mobility of the proteins. The major differences in the relaxation behavior of elastin between arteries cultured with physiological and pathological concentrations of homocysteine are discussed. 相似文献