The American Wei

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Contrôle photochimique de machines moléculaires (Rotaxanes construits sur un complexe octaédrique à trois chélates)

Ce travail s'inscrit dans le domaine des machines moléculaires. Il décrit la synthèse d'un [2]-rotaxane dont l'anneau peut être mis en mouvement, sous l'action de la lumière visible puis de la chaleur.Dans une première partie est exposée la synthèse d'un nouveau ligand tétradentate comportant deux phénanthrolines. Il coordine le fer(II) et le ruthénium(II) en formant un axe passant par le métal, long d'environ 20Å. Il a permis l'obtention du premier complexe linéaire du type [Ru(diimine)3]2+.La stabilité configurationnelle exceptionnelle du complexe mononucléaire de fer(II) de ce ligand a été mise en évidence, en collaboration, par le groupe de Jérôme Lacour à Genève, grâce à l'interaction purement ionique du complexe cationique avec un anion chiral. Cette stabilité a été mise à profit pour séparer, par des techniques chromatographiques, les hélices droite et gauche du complexe. Elle a ensuite permis la synthèse asymétrique de son hélice droite avec une bonne stéréosélectivité.Pour la première fois, un [2]-rotaxane a été construit autour d'un complexe octaédrique de ruthénium(II), grâce à la géométrie linéaire des complexes étudiés en première partie. Tout d'abord, un pseudo-rotaxane basé sur un complexe du type [Ru(diimine)3]2+ a été synthétisé, en enfilant et coordinant une bipyridine encombrée cyclique sur un complexe axial de ruthénium(II). Des études RMN approfondies ont montré que le complexe existait également sous une forme non enfilée, qu'il a été impossible de séparer du pseudo-rotaxane. Néanmoins, l'état excité du pseudo-rotaxane, généré par irradiation lumineuse, a permis de décoordiner et d'expulser sélectivement l'anneau du centre métallique. Un [2]-rotaxane a ensuite été préparé en ajoutant des groupements bloquants au pseudo-rotaxane. Il est également contaminé par la présence de son isomère non-enfilé mais ses propriétés dynamiques ont été mises en évidence.This work, part of the field of molecular machines, describes the synthesis of a [2]-rotaxane, in which the ring can be set into motion, under the action of visible light and then of heat.In a first part, the synthesis of a new tetradentate ligand, bearing two phenanthrolines, is described. Under coordination to iron(II) and ruthenium(II), it defines an axle runing through the metal centre, with an approximate lenght of 20Å. This ligand enabled the synthesis of the first linear complex of the [Ru(diimine)3]2+ type.The unusual configurationnal stability of the mononuclear iron(II) complex of this ligand has been evidenced, in collaboration, by the group of Jérôme Lacour in Geneva, using the ionic interaction of the cationic complex with a chiral anion. This stability allowed the separation of the left and right-handed helices of the complex via chromatographic techniques. An asymmetric synthesis of the right-handed helice was then achieved.A [2]-rotaxane was synthesized for the first time around an octahedral ruthenium(II) complex, taking advantage of the linear shape of the complexes described in the first part. First, a pseudo rotaxane of the [Ru(diimine)3]2+ type was obtained, by threading and coordinating a cyclic bipyridine on an axial ruthenium(II) complex. NMR studies showed that the complex also existed under a non-threaded form, which was impossible to separate from the pseudo-rotaxane. Nevertheless, its excited state, generated under visible light irradiation, allowed the selective decoordination and expulsion of the ring from the metal centre. A [2]-rotaxane has then been prepared, by attaching bulky stoppers to the pseudo-rotaxane. It is also contaminated by the presence of its unthreaded isomer but its dynamic properties have been evidenced.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Templated Synthesis of a Rotaxane with a[Ru(diimine)3]2+ Core

International audienc

Execução fiscal e recuperação judicial; competência: Lei n. 13.043/2014 [Jurisprudência comentada]

Comentário ao AgRg no CC 136.130/SP do Superior Tribunal de Justiça.Ministro relator: Antonio Carlos Ferreira.Ementa: Execução Fiscal e Recuperação Judicial. Competência do Juízo Universal. Edição da Lei nº 13.043, de 13.11.2014. Parcelamento de Créditos de Empresa em Recuperação. Jurisprudência Mantida

Ion-Pair Mediated Asymmetric Synthesis of a Configurationally Stable Mononuclear Tris(diimine) Iron(II) Complex

Configurational stability is conferred on the complex 1 (R=4-MeOC6H4) by the carefully designed tetradentate bis(1,10-phenanthroline) ligand. The resolution and asymmetric synthesis of 1 were readily achieved by using tris(tetrachlorobenzenediolato)phosphate(V) anions (2) as chiral auxiliaries. The picture shows the separation of the enantiomers of 1 by preparative ion-pair thin-layer chromatography

Long‐Lived MLCT Excited States‐Ru II Complexes with a Helical Bis‐Phen Ligand

International audienceThe synthesis of a new RuII complex [Ru(L1)(4,7-dpphen)]2+, bearing a tetradentate bis-1,10-phenanthroline ligand L1, is described. X-ray crystal structure analysis shows that the tetradentate ligand L1 coils around the metal and occupies both axial and two of the equatorial positions of the complex. 1H NMR studies clearly indicate that the complex has C2 symmetry in solution. The room temperature luminescence properties of [Ru(L1)(4,7-dpphen)]2+ have been studied, as have those of the related complex [Ru(L2)(4,4′-dmbp)]2+. For both complexes, the luminescence quantum yields and lifetimes are three to ten times higher than those of [Ru(bpy)3]2+. These unusual results are explained by the geometrical constraints imposed by the tetradentate ligands L1 and L2 in their respective complexes, resulting in an effective decoupling between the 3MLCT and 3MC excited state

Probing the electronic structure and photophysics of thiophene–diketopyrrolopyrrole derivatives in solution

International audienceDiketopyrrolopyrroles are a popular class of electron-withdrawing unit in optoelectronic materials. When combined with electron donating side-chain functional groups such as thiophenes, they form a very broad class of donor-acceptor molecules: thiophene-diketopyrrolopyrroles (TDPPs). Despite their widescale use in biosensors and photovoltaic materials, studies have yet to establish the important link between the electronic structure of the specific TDPP and the critical optical properties. To bridge this gap, ultrafast transient absorption with 22 fs time resolution has been used to explore the photophysics of three prototypical TDPP molecules: a monomer, dimer and polymer in solution. Interpretation of experimental data was assisted by a recent high-level theoretical study, and additional density functional theory calculations. These studies show that the photophysics of these molecular prototypes under visible photoexcitation are determined by just two excited electronic states, having very different electronic characters (one is optically bright, the other dark), their relative energetic ordering and the timescales for internal conversion from one to the other and/or to the ground state. The underlying difference in electronic structure alters the branching between these excited states and their associated dynamics. In turn, these factors dictate the fluorescence quantum yields, which are shown to vary by B1-2 orders of magnitude across the TDPP prototypes investigated here. The fast non-radiative transfer of molecules from the bright to dark states is mediated by conical intersections. Remarkably, wavepacket signals in the measured transient absorption data carry signatures of the nuclear motions that enable mixing of the electronic-nuclear wavefunction and facilitate non-adiabatic coupling between the bright and dark states