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Your search keyword '"Sylvie Létard"' showing total 4 results
Start Over Author "Sylvie Létard" Topic 0104 chemical sciences
4 results on '"Sylvie Létard"'

1. Organic crystals for second harmonic generation switching based on anil photochromes

Author

Arnaud Spangenberg, Pei Yu, Sylvie Létard, Michel Sliwa, Rémi Métivier, Keitaro Nakatani, Laboratoire Avancé de Spectroscopie pour les Intéractions la Réactivité et l'Environnement - UMR 8516 (LASIRE), Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Centrale Lille Institut (CLIL), Laboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires (PPSM), École normale supérieure - Cachan (ENS Cachan)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de chimie inorganique (LCI), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), and Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)

Subjects
second harmonic generation, business.industry, Chemistry, Second-harmonic generation, Nonlinear optics, 02 engineering and technology, General Chemistry, photochromism, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, switch, non-linear optics, 0104 chemical sciences, 3. Good health, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Photochromism, Acentric factor, Optoelectronics, [CHIM.OTHE]Chemical Sciences/Other, 0210 nano-technology, business
Abstract

In photochromic materials, we demonstrated that non-linear optical (NLO) properties such as second harmonic generation (SHG) can be switched reversibly by alternate UV and visible irradiations. We report here on the design of materials fulfilling the prerequisites for SHG activity (push-pull and acentric space group) and photochromic properties. Photochromic and NLO properties of a series of anils are presented, along with the ability of some of them to switch SHG.

Published
2008
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2. Design, Synthesis, Structural and Nonlinear Optical Properties of Photochromic Crystals: Toward Reversible Molecular Switches

Author

Hiroshi Masuhara, Sylvie Létard, Keitaro Nakatani, Michel Sliwa, Isabelle Malfant, Pei Yu, Pascal G. Lacroix, Martine Nierlich, Tsuyoshi Asahi, Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université de Bordeaux (UB), Laboratoire de chimie de coordination (LCC), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de chimie inorganique (LCI), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires (PPSM), and École normale supérieure - Cachan (ENS Cachan)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Molecular switch, business.industry, Hydrogen bond, Chemistry, General Chemical Engineering, Second-harmonic generation, 02 engineering and technology, General Chemistry, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Tautomer, 0104 chemical sciences, 3. Good health, Crystal, Crystallography, Photochromism, Materials Chemistry, Optoelectronics, Molecule, 0210 nano-technology, business, Visible spectrum
Abstract

Two new anil molecules exhibiting photochromism in the crystalline state, N-(4-hydroxy)-salicylidene-amino-4-(methylbenzoate) (2) and N-(3,5-di-tert-butylsalicylidene)-4-aminopyridine (3), are obtained. Upon irradiation in the UV, the yellow crystals change color to red, owing to enol-keto intramolecular tautomerism. The red color disappears, when crystals are left in the dark or irradiated with visible light. 3 has the most stable keto form among all anil-type photochromic compounds (τ = 460 days at room temperature). Both exhibit nonlinear optical (NLO) properties and show powder second harmonic generation (SHG) of respectively 10 and 3 times vs urea. X-ray diffraction shows acentric structures where molecules line up “head-to-tail” through hydrogen bonds for 2 (space group Pc), or form a chiral helix 3 (space group P32). Evidence of reversible structural change is given for 3, and we demonstrate the functionality of this crystal as an NLO switching material, as SHG can be photomodulated by about 30%.

Published
2005
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3. Complete temperature study of the relaxation from the high-spin state to low-spin state in a strongly cooperative spin crossover compound

Author

Noëlle Lascoux, Eric Freysz, S. Montant, Guillaume Chastanet, Jérôme Degert, Sylvie Létard, Jean-François Létard, Centre de physique moléculaire optique et hertzienne (CPMOH), Université Sciences et Technologies - Bordeaux 1-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), and Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université de Bordeaux (UB)

Subjects
Condensed matter physics, Spin states, Photo-induced effect, 010405 organic chemistry, Chemistry, Hysteresis, Kinetics, Temperature, General Physics and Astronomy, Transition system, [CHIM.MATE]Chemical Sciences/Material chemistry, 010402 general chemistry, 01 natural sciences, 0104 chemical sciences, Low spin, Relaxation rate, Spin crossover, High spin, Relaxation (physics), Physical and Theoretical Chemistry, Constant (mathematics)
Abstract

Using two complementary techniques, the relaxation of a photo-induced spin state transition in a strongly cooperative compound has been studied from 10 to 170 K. Up to 150 K, the relaxation rate increases with temperature. At higher temperature, the stabilization of the high-spin state results in a decrease of the relaxation rate. Within the hysteresis loop, as one approaches the switching temperature branch, a critical slowing down of the kinetics and a constant decrease of the cooperative contribution are recorded. This study evidences, for the first time, the complex temperature evolution of the relaxation of photo-induced spin state transition.

Published
2005
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4. Single laser pulse induces spin state transition within the hysteresis loop of an iron compound

Author

Jean-François Létard, Eric Freysz, Sylvie Létard, Sébastien Montant, Centre de physique moléculaire optique et hertzienne (CPMOH), Université Sciences et Technologies - Bordeaux 1-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), and Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université de Bordeaux (UB)

Subjects
Spin states, Iron, General Physics and Astronomy, Inorganic compounds, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Molecular physics, law.invention, Metal, Single laser pulse, law, Physical and Theoretical Chemistry, Spin (physics), Thermal hysteresis, Condensed matter physics, Photoconversion, Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, Laser, 0104 chemical sciences, Pulse (physics), Loop (topology), visual_art, visual_art.visual_art_medium, 0210 nano-technology
Abstract

Within the thermal hysteresis loop of the [Fe(PM-BiA) 2 (NCS) 2 ] compound, a single laser pulse of 14 mJ cm −2 induces a photo-conversion from the low spin (LS, S = 0) to the high spin (HS, S = 2) state of the Fe 2+ metallic center. The temporal dynamic of this phenomena indicates that the system is firstly photo-excited into the HS state and then slowly relaxes to a mixture of HS/LS state. Subsequent laser pulses do not affect the HS/LS ratio. The system can be brought back to its initial LS state by adjusting the temperature of the compound. A simple model accounts qualitatively for the observed phenomenon.

Published
2004
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