Prediction of photophysical properties of pyrimidine chromophores using Taguchi method

International audienceThis paper presents the photophysical properties of a series of pyrimidine chromophores. The influence of three parameters has been studied: the nature of the electron-donating group and of the π-conjugated linker as well as the substituted position of the pyrimidine core (2, 4 and 6 position). Taguchi design of experiment combined with analysis of variance methodologies have been employed. This approach has permitted to highlight the main factor affecting the absorption and emission wavelengths of the studied compounds. Absorption maxima of this family of compounds can be predicted with relatively good precision (±18 nm). The emission maxima can be also predicted, however the precision is lower (±39 nm). Taguchi methodology has been also employed with these families of compounds to optimize the intramolecular charge transfer estimated by emission solvatochromy

Hommage à Pierre Courtin (1921-2012)

Propos recueillis par Marie-Cécile Miessner. Emmanuel Pernoud « De pauvres choses minces ou épaisses trouées par endroits » Un pavillon de banlieue, le déjeuner s’éternise, on a bien mangé et bien bu, on a parlé de tout et de rien. Vers les 15 heures, il est temps de travailler, de préparer l’exposition. On vous emmène à la cave. On imaginait trouver des cartons de gravures, du papier imprimé ; on tombe sur du travail d’orfèvre, de grandes plaques de métal recouvertes de signes mystérieux qui..

Recent advances in pyrimidine derivatives as luminescent, photovoltaic and non-linear optical materials.

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Evaluation de réactions asymétriques en liquides ioniques

Ce travail décrit la synthèse et l'exploitation de liquides ioniques achiraux et chiraux. Différentes réactions asymétriques ont été étudiées dans les liquides ioniques et les résultats ont été comparés à ceux obtenus dans les solvants organiques usuels. Dans un premier temps, divers liquides ioniques ou sels de type imidazolium achiraux et chiraux ont été préparés. Par la suite, une voie de synthèse a été envisagée pour la préparation de pyridiniums en série 1,3-dioxane. Pour cela, la réaction de Heck a été évaluée en solvants organiques puis en liquides ioniques. Nous avons également développé la synthèse de pyridiniums porteurs d'une chiralité axiale en série carbocyclique en version racémique. Dans un second temps, diverses réactions ont été évaluées en liquides ioniques et en solvants organiques afin de comparer les résultats. Aucune amélioration des résultats n'a été observée lors de l'étude des réactions de Michael et de Diels-Alder asymétriques en liquides ioniques. Cependant, des résultats très encourageants ont été obtenus pour la réaction de Mukaiyama. Finalement, la dernière partie de notre travail a été consacrée à la fluoration électrophile énantiosélective d'énoxysilanes faisant intervenir des ammoniums [N-F]+ chiraux dérivés des alcaloïdes du quinquina. Dans le cadre de cette étude, les liquides ioniques se sont révélés être de bons solvants, en effet, les résultats obtenus sont du même ordre de grandeur, voire supérieurs à ceux obtenus dans l'acétonitrile.This work describes the synthesis and the exploitation of achiral and chiral ionic liquids. Various asymmetric reactions were studied in ionic liquids and the results were compared with those obtained in usual organic solvents. In a first time, various achiral and chiral imidazolium ionic liquids or salts were prepared. Then, a pathway of synthesis considered for the preparation of 1,3-dioxane pyridiniums. For that the Heck reaction was evaluated in organic solvents then in ionic liquids. We also developed the synthesis of racemic pyridiniums with axial chirality in carbocyclic series. In a second time, various reactions have been evaluated in ionic liquids in order to compare the results with those obtained in organic solvents. The results show no improvement for asymmetric Michael reaction and Diels-Alder reaction in ionic liquids. However, encouraging results were obtained in Mukaiyama reaction. Eventually, the last part of our work was devoted to electrophilic enantioselective fluorination of silyl enol ethers, incorporating chiral fluorinating agents [N-F]+ derived from cinchona alkaloids. In these conditions, ionic liquids proved to be good solvents, in fact, the results obtained compared favorably with those obtained in acetonitrile.ROUEN-BU Sciences (764512102) / SudocSudocFranceF

Luminescent materials incorporating pyrazine or quinoxaline moieties

International audienceThough the past few decades, the development of new luminescent materials has received a lot of attention due to their applications as fluorescent sensors, in biological microscopy and in optoelectronic devices. Most of these applications are relied on intramolecular charge transfer (ICT). Presence of electron withdrawing N-heterocycles such as pyrazine and quinoxaline rings appeared therefore particularly interesting to be used as electron-attracting part in π-conjugated structures. Moreover, presence of nitrogen atoms with lone electron pairs allows to the pyrazine and the quinoxaline ring to act as effective and stable complexing agent or as base that can be protonated. This review reports luminescent small molecules and oligomers including a pyrazine or quinoxaline ring in their scaffold highlighting their applications related to photoluminescence and electroluminescence

Palladium-catalyzed direct C-H functionalization: a powerful methodology to access tailor-made GFP analogs and biologically-active molecules

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Highly enantioselective organocatalytic formation of a quaternary carbon center via chiral Brønsted acid catalyzed self-coupling of enamides

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Organocatalysis with Chiral Formamides: Asymmetric Allylation and Reduction of Imines

International audienceSimple aldimine, derived from p‐nitrobenzaldehyde and 2‐aminophenol, reacts with allyltrichlorosilane in the presence of chiral N‐formylproline activator 5 and an L‐proline additive to afford the corresponding homoallylic amine in good yield (84 %) and with moderate enantioselectivity (43 % ee). The role of the second formamide moiety in the activator is crucial to bring about the enhancement in the reaction rate and enantioselectivity, as C2‐chiral bisformamide 1 promotes for the same allylation reaction in higher yield (94 %) and enantioselectivity (83 % ee). Chiral monoformamide 5 (10 mol‐%), with the assistance of HMPA as an additive, also catalyses the asymmetric reduction of ketimine 13 in the presence of trichlorosilane in good yield and enantioselectivity (75 %, 81 % ee)

Palladium-catalyzed direct C-H functionalization: a powerful methodology to access tailor-made GFP analogs and biologically-active molecules

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Organometallic Fluorophores of d8 Metals (Pd, Pt, Au)

International audienceIn this contribution, we review the state-of-the-art in the field of the synthesis and luminescent properties of cyclometalated complexes of noble d8 metals Pd(II), Pt(II), and Au(III), with a large variety of organic ligands. For platinum and gold complexes, special emphasis has been done in the last 3 years (2015–17), because a huge number of outstanding contributions of academic and even industrial interest have appeared in this short period of time, while cyclopalladated complexes have been analyzed with a wider temporal perspective. The intrinsic properties of the metals (oxidation state, geometry, electrophilic character, redox behavior) and the ligands (type of donor atoms, σ-donating strength, π-accepting ability, planarity, rigidity) have been analyzed to determine their influence in the synthesis, through different methods, of the respective cyclometalated complexes, and also in the photophysical properties (type of transitions, tuning as a function of the substituents, etc.). In some selected cases, the application of these complexes to industrial optical devices is presented