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Régis Réau

Publications and source records attributed to Régis Réau.

15 recordsLinked to original sources
PubMed2006

Tuning of electronic properties in thienyl-phosphole pi-conjugated systems through P-functionalization monitored by Raman spectroscopy.

Herein, a Raman spectroscopic study of a new family of 2,5-di(2-thienyl)phospholes and thienyl-capped 1,1'-diphospholes is presented. The Raman spectra have been carefully assigned with the help of density functional calculations. For di(2-thienyl)phospholes, two well-differentiated groups of Raman bands exist that arise either from the central phosphole ring or from the outer thiophene substituents. These data reveal a segmentation of the electronic structure. This paper reports interesting relationships between geometrical data such as the BLA (bond-length alternation) parameter and Raman band wavenumbers. These correlations are unprecedented in the chemistry of phospholes and have been used to interpret the evolution of the electronic structure (aromaticity=pi-conjugation) upon 1) substitution of the central sulfur atom of terthiophene by phosphorus and 2) P-functionalization. Increasing the coordination number of the phosphole ring results in intramolecular charge transfer. The best scenario for phosphole aromaticity is found for 1,1'-diphospholes.

Journal Article↗
PubMed2006

Mimicking [2,2]paracyclophane topology: molecular clips for the coordination-driven cofacial assembly of pi-conjugated systems.

Self-assembly of CuI dimers, featuring a bridging phosphole ligand, and ditopic cyano-substituted chromophores affords nanosize supramolecular cationic rectangles. Due to the short Cu-Cu distance in the bimetallic clips, the coordinated chromophores are forced to participate in cofacial pi-pi interactions as evidenced by X-ray data. In addition, intermolecular pi-pi interactions in the solid state are observed leading to infinite columns of pi-stacked (para-phenylenevinylene)-based chromophores.

Journal Article↗
PubMed2006

Toward functional pi-conjugated organophosphorus materials: design of phosphole-based oligomers for electroluminescent devices.

The photophysical, electrochemical, and optoelectronic properties of conjugated systems incorporating dibenzophosphole or phosphole moieties are described. Dibenzophosphole derivatives are not suitable materials for OLEDs due to their weak photoluminescence (PL) in the solid state and the instability of the devices. Variation of the substitution pattern of phospholes and chemical modification of their P atoms afford thermally stable derivatives, which are photo- and electroluminescent. Comparison of the optical properties of solution and thin film of thioxophospholes shows that these compounds do not form aggregates in the solid state. This property, which is also supported by an X-ray diffraction study of three novel derivatives, results in an enhancement of the fluorescence quantum yields in the solid state. In contrast, (phosphole)gold(I) complexes exhibit a broad emission in thin film, which is due to the formation of aggregates. Single- and multilayer OLEDs using these P derivatives as the emissive layer have been fabricated. The emission color of these devices and their performances vary with the nature of the P material. Interestingly, di(2-thienyl)thiooxophosphole is an efficient host for the red dopant DCJTB, and devices using the gold complexes have broad emission spectra.

Journal Article↗
PubMed2005

Mechanistic studies on a novel, highly potent gold-phosphole inhibitor of human glutathione reductase.

The homodimeric flavoprotein glutathione reductase (GR) is a central player of cellular redox metabolism, connecting NADPH to the large pool of redox-active thiols. In this work, the inhibition of human GR by a novel gold-phosphole inhibitor (GoPI) has been studied in vitro. Two modes of inhibition are observed, reversible inhibition that is competitive with GSSG followed by irreversible inhibition. When approximately 1 nm GoPI is incubated with NADPH-reduced GR (1.4 nm) the enzyme becomes 50% inhibited. This appears to be the most potent stable inhibitor of human GR to date. Analyzing the monophasic oxidative half-reaction of reduced GR with GSSG at pH 6.9 revealed a K(d)((app)) for GSSG of 63 microm, and a k((obs)max) of 106 s(-1) at 4 degrees C. The reversible inhibition by the gold-phosphole complex [{1-phenyl-2,5-di(2-pyridyl)phosphole}AuCl] involves formation of a complex at the GSSG-binding site of GR (K(d) = 0.46 microm) followed by nucleophilic attack of an active site cysteine residue that leads to covalent modification and complete inactivation of the enzyme. Data from titration spectra, molecular modeling, stopped-flow, and steady-state kinetics support this theory. In addition, covalent binding of the inhibitor to human GR was demonstrated by mass spectrometry. The extraordinary properties of the compound and its derivatives might be exploited for cell biological studies or medical applications, e.g. as an anti-tumor or antiparasitic drug. Preliminary experiments with glioblastoma cells cultured in vitro indicate an anti-proliferative effect of the inhibitor in the lower micromolar range.

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PubMed2004

Connecting pi-chromophores by sigma-P-P bonds: new type of assemblies exhibiting sigma-pi-conjugation.

To study the ability of sigma-P-P skeleton to mediate interaction between pi-chromophores, 1,1'-biphospholes bearing phenyl or thienyl substituents at the 2,2' and 5,5'-position have been prepared and studied. These air-stable derivatives are readily available via a "one-pot" synthesis starting from diynes. Theoretical studies and UV-vis data clearly establish that the two pi-systems interact via the sigma-P-P bridge. This through-bond interaction results in a lowering of the optical HOMO-LUMO gap of the assemblies. The nucleophilic sigma(3)-P centers of these 1,1'-biphospholes allow chemical modifications of the sigma-bridge. These modifications offer further tuning of the optical properties of the assembly. Electrooxidation of the thienyl-substituted 1,1'-biphosphole results in electroactive materials characterized by low optical band gap and reversible p-doping.

Journal Article↗
PubMed2003

Synthesis and electronic properties of alternating alpha,alpha'-thiophene-phosphole oligomers.

[structure: see text] Alternating thiophene-phosphole oligomers up to seven rings in length have been synthesized. A regular decrease of the HOMO-LUMO gap is observed upon increasing the length of the pi-conjugated system. The nature of the P-moieties dramatically influences the optical and electrochemical properties of these phosphole-based oligomers. Electro-oxidation of derivative 5a afforded an electroactive polymer exhibiting reversible p-doping.

Journal Article↗
PubMed2003

Chemistry of bridging phosphanes: PdI dimers bearing 2,5-dipyridylphosphole ligands.

Two synthetic routes to Pd(I) dimers that feature a bridging 1-phenyl- and 1-cyclohexyl-2,5-di(2-pyridyl)phosphole ligand, 3 a and 3 b, respectively, are described. The first involves a conproportionation process between Pd(II) and Pd(0) complexes, while the second involves ligand displacement from a preformed Pd(I) dimer. Both routes are operable for 1-phenylphosphole 1 a, whereas the former failed with 1-cyclohexylphosphole 1 b. A mechanistic study revealed that the conproportionation pathway implies a reversible oxidative addition of the P-C(phenyl) bond of Pd(II)-coordinated 1 a to Pd(0) leading to a bimetallic Pd(II) complex 5. The structures of complexes 3 a and 3 b were studied by means of X-ray diffraction. The similarity of these solid-state structures suggests that the bridging mode of the P atom is due to mu-1kappaN:1,2kappaP:2kappaN coordination of ligands 1 a, b. The electrochemical behaviour and UV/Vis absorption properties of complexes 3 a, b are reported. Complex 3 a is inert towards CO, PPh(3) and 1,3-dipoles. It reacted with dimethylacetylene dicarboxylate to give complex 6 as a result of insertion of the alkyne into the Pd-Pd bond. X-ray diffraction studies of complexes 5 and 6 are also presented.

Journal Article↗
PubMed2003

First examples of organophosphorus-containing materials for light-emitting diodes.

Exploiting the reactivity of the P-atom of phosphole-based oligomers, we have achieved access to the first organophosphorus-containing organic light-emitting diode (OLED) materials. The versatility of these P-materials is demonstrated with the synthesis of a corresponding gold complex that has also been used as an OLED material. Optimization of the OLED devices by doping the phosphole layer with a red fluorescent dye is described.

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