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131.
Ebrahimi-Fard Kurusch José M. Gracia-Bondía Frédéric Patras 《Letters in Mathematical Physics》2007,81(1):61-75
The word problem for an arbitrary associative Rota–Baxter algebra is solved. This leads to a noncommutative generalization
of the classical Spitzer identities. Links to other combinatorial aspects are indicated.
相似文献
132.
Dhont Guillaume Cassam-Chenaï Patrick Patras Frédéric 《Journal of mathematical chemistry》2021,59(10):2294-2326
Journal of Mathematical Chemistry - The construction of integrity bases for invariant and covariant polynomials built from a set of three dimensional vectors under the $${{\mathrm {SO(3)}}}$$ and... 相似文献
133.
Cyclodimerization versus Polymerization of Methyl Methacrylate Induced by N‐Heterocyclic Carbenes: A Combined Experimental and Theoretical Study 下载免费PDF全文
Winnie Nzahou Ottou Damien Bourichon Dr. Joan Vignolle Anne‐Laure Wirotius Dr. Fredéric Robert Prof. Yannick Landais Dr. Jean‐Marc Sotiropoulos Dr. Karinne Miqueu Prof. Daniel Taton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(14):3989-3997
The activation behavior of two N‐heterocyclic carbenes (NHCs), namely, 1,3‐bis(isopropyl)imidazol‐2‐ylidene(NHCiPr) and 1,3‐bis(tert‐butyl) imidazol‐2‐ylidene (NHCtBu), as organic nucleophiles in the reaction with methyl methacrylate (MMA) is described. NHCtBu allows the polymerization of MMA in DMF at room temperature and in toluene at 50 °C, whereas NHCiPr reacts with two molecules of MMA, forming an unprecedented imidazolium–enolate cyclodimer (NHCiPr/MMA=1:2). It is proposed that the reaction mechanism occurs by initial 1,4‐nucleophilic addition of NHCiPr to MMA, generating a zwitterionic enolate 2 , followed by addition of 2 to a second MMA molecule, forming a linear imidazolium–enolate 3 (NHCiPr/MMA=1:2). Proton transfer, generating intermediate 5 , followed by cyclization and release of methanol yielded the aforementioned zwitterionic cyclodimer 1:2 adduct 7 , the molecular structure of which has been established by NMR spectroscopy, X‐ray diffraction, and mass spectrometry. This unexpected difference between NHCtBu and NHCiPr in the reaction with MMA (polymerization and cyclodimerization, respectively) can be rationalized by using DFT calculations. In particular, the nature of the NHC strongly influences the cyclodimerization pathway, the cyclization of 5 and the release of methanol are the discriminating step and limiting step, respectively. In the case of NHCtBu, both steps are strongly disfavoured compared with that of NHCiPr (energetic difference of around 14 and 9 kcal mol?1, respectively), preventing the cyclization mechanism from a kinetic viewpoint. Moreover, addition of a third molecule of MMA in the polymerization pathway results in a lower activation barrier than that of the limiting step in the cyclodimerization pathway (difference of around 14 kcal mol?1), in agreement with the formation of polymethyl methacrylate (PMMA) by using NHCtBu as nucleophile. 相似文献
134.
Experimental and Theoretical Investigation of the First‐Order Hyperpolarizability of Octupolar Merocyanine Dyes 下载免费PDF全文
Dr. Frédéric Castet Dr. Mireille Blanchard‐Desce Frédéric Adamietz Yevgen M. Poronik Prof. Dr. Daniel T. Gryko Prof. Dr. Vincent Rodriguez 《Chemphyschem》2014,15(12):2575-2581
Hyper‐Rayleigh scattering experiments and quantum chemical calculations are combined to investigate the second‐order nonlinear optical responses of a series of three‐arm merocyanine derivatives. They exhibit an octupolar hyperpolarizability response with lower amplitude than crystal violet due to a lower extent of the photoinduced charge transfer and reduced bond length alternation. Strong effects on the second‐order optical response measured close to the two‐photon absorption level are clearly evidenced; for example, the effective measured polarization ratio deviates below the ideal octupolar value of 3/2 even at very low excitation power. These effects are attributed to two‐photon absorption resonance, which we believe modifies dynamically the population of the ground state versus that of the excited state. 相似文献
135.
Serhii Krykun Maksym Dekhtiarenko David Canevet Vincent Carr Frdric Aubriet Eric Levillain Magali Allain Zoia Voitenko Marc Sall Sbastien Goeb 《Angewandte Chemie (International ed. in English)》2020,59(2):716-720
Developing methodologies for on‐demand control of the release of a molecular guest requires the rational design of stimuli‐responsive hosts with functional cavities. While a substantial number of responsive metallacages have already been described, the case of coordination‐tweezers has been less explored. Herein, we report the first example of a redox‐triggered guest release from a metalla‐assembled tweezer. This tweezer incorporates two redox‐active panels constructed from the electron‐rich 9‐(1,3‐dithiol‐2‐ylidene)fluorene unit that are facing each other. It dimerizes spontaneously in solution and the resulting interpenetrated supramolecular structure can dissociate in the presence of an electron‐poor planar unit, forming a 1:1 host–guest complex. This complex dissociates upon tweezer oxidation/dimerization, offering an original redox‐triggered molecular delivery pathway. 相似文献
136.
Lucie Appy Anaïs Depaix Xavier Bantreil Frédéric Lamaty Suzanne Peyrottes 《Phosphorus, sulfur, and silicon and the related elements》2020,195(11):930-931
AbstractWe have developed original one-pot and protecting group-free approaches, which are also user-friendly and reliable, to synthesize nucleotides and derivatives starting from nucleoside 5’-monophosphates. Both methods present convenient set-up, i.e., non-dry solvents and reagents, substrates in their sodium or acid form, and commercially available and cheap phosphorus reagents as sodium and potassium salts. 相似文献
137.
Morgane Rosendale Jonathan Daniel Frdric Castet Paolo Pagano Jean-Baptiste Verlhac Mireille Blanchard-Desce 《Molecules (Basel, Switzerland)》2022,27(7)
Molecular-based Fluorescent Organic Nanoparticles (FONs) are versatile light-emitting nano-tools whose properties can be rationally addressed by bottom-up molecular engineering. A challenging property to gain control over is the interaction of the FONs’ surface with biological systems. Indeed, most types of nanoparticles tend to interact with biological membranes. To address this limitation, we recently reported on two-photon (2P) absorbing, red to near infrared (NIR) emitting quadrupolar extended dyes built from a benzothiadiazole core and diphenylamino endgroups that yield spontaneously stealth FONs. In this paper, we expand our understanding of the structure-property relationship between the dye structure and the FONs 2P absorption response, fluorescence and stealthiness by characterizing a dye-related series of FONs. We observe that increasing the strength of the donor end-groups or of the core acceptor in the quadrupolar (D-π-A-π-D) dye structure allows for the tuning of optical properties, notably red-shifting both the emission (from red to NIR) and 2P absorption spectra while inducing a decrease in their fluorescence quantum yield. Thanks to their strong 1P and 2P absorption, all FONs whose median size varies between 11 and 28 nm exhibit giant 1P (106 M−1.cm−1) and 2P (104 GM) brightness values. Interestingly, all FONs were found to be non-toxic, exhibit stealth behaviour, and show vanishing non-specific interactions with cell membranes. We postulate that the strong hydrophobic character and the rigidity of the FONs building blocks are crucial to controlling the stealth nano-bio interface. 相似文献
138.
Philippe M. Loiseau Kaluvu Balaraman Gillian Barratt Sbastien Pomel Rmy Durand Frdric Frzard Bruno Figadre 《Molecules (Basel, Switzerland)》2022,27(7)
There is a need for new, cost-effective drugs to treat leishmaniasis. A strategy based on traditional medicine practiced in Bolivia led to the discovery of the 2-substituted quinoline series as a source of molecules with antileishmanial activity and low toxicity. This review documents the development of the series from the first isolated natural compounds through several hundred synthetized molecules to an optimized compound exhibiting an in vitro IC50 value of 0.2 µM against Leishmania donovani, and a selectivity index value of 187, together with in vivo activity on the L. donovani/hamster model. Attempts to establish structure–activity relationships are described, as well as studies that have attempted to determine the mechanism of action. For the latter, it appears that molecules of this series act on multiple targets, possibly including the immune system, which could explain the observed lack of drug resistance after in vitro drug pressure. We also show how nanotechnology strategies could valorize these drugs through adapted formulations and how a mechanistic targeting approach could generate new compounds with increased activity. 相似文献
139.
Jacqueline Destain Patrick Fickers Frédéric Weekers Benoît Moreau Philippe Thonart 《Applied biochemistry and biotechnology》2005,121(1-3):269-277
In this article, we report the development and optimization of an industrial culture medium for the production of extracellular
lipase in the yeast Yarrowia lipolytica. Until now olive oil in combination with glucose was used as the carbon source and inducer for the production of lipase.
Our results demonstrate that methyloleate, a cheap hydrophobic compound, could efficiently substitute olive oil as the inducer
and carbon source for lipase production. A new process of lipase production was developed yielding a twofold increase in the
level of production compared with the levels in previous reports. 相似文献
140.
Eddy Thiriot Sébastien Canneaux Eric Hénon Frédéric Bohr 《Reaction Kinetics and Catalysis Letters》2005,85(1):123-129
Summary We show the presence of an ether group in alkoxy radicals significantly lowers the activation energy of the b-C-H dissociation and only slightly increases the isomerization barrier. Moreover, an 1-6 isomerization mechanism involving a 7-membered transition state may compete with the usual 1-5 isomerization. 相似文献