Agnes. Chartier | Université d'Orléans (Loire Valley University) (original) (raw)
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Papers by Agnes. Chartier
European Journal of Organic Chemistry, 2015
ABSTRACT The first efficient synthesis of various 1,4-disubstituted pyrido[1′,2′:1,5]pyrazolo[3,4... more ABSTRACT The first efficient synthesis of various 1,4-disubstituted pyrido[1′,2′:1,5]pyrazolo[3,4-d]pyridazines is reported. The reactivity toward chlorine release at the C-1 and C-4 positions was investigated. SNAr and palladium-catalysed cross-coupling reactions were carried out, and conditions were optimised for each procedure. 1,4-Bis(het)aryl derivatives were obtained under a Suzuki cross-coupling procedure whereas SNAr substitution was achieved mainly at C-1 in preference to C-4. The monosubstituted C-4 morpholino derivative was used as a starting material to provide dissymmetrical 1,4-diaminated or 1-(het)aryl-4-morpholino products.
Talanta, 2013
Kahweol and cafestol are two diterpenes that exist mainly as esters of fatty acids in green coffe... more Kahweol and cafestol are two diterpenes that exist mainly as esters of fatty acids in green coffee oil. To recover them under their free form they have to be either saponified or trans-esterified. These two compounds are well known to be sensitive to heat, and reagents, therefore experimental conditions used in the transesterification reaction are critical. In this paper, a Doehlert experimental design plan is used to optimize the transesterification conditions using some key variables such as the temperature of the reaction, the reagent base concentration and the duration of the reaction. Therefore, the optimal parameters determined from the Doehlert design are equal to 70 1C, temperature of the reaction; 1.25 mol L À 1 concentration of the reagent base; and 60 min reaction time. The contour plots show that the extracted quantity of kahweol and cafestol can depend greatly from the experimental conditions. After transesterification, the free form of the diterpernes is extracted from the lipid fraction using liquidliquid extraction and analyzed using GC-FID without prior derivatization. The amount of kahweol and cafestol obtained from green coffee oil obtained by cold mechanical press of Catuai coffee bean is equal to 33.27 2.2 and 24.372.4 g kg À 1 oil, respectively. In an attempt to streamline the process, the transesterification reaction is performed in an in-flow chemistry reactor using the optimal conditions obtained with the Doehlert experimental design. The amount of kahweol and cafestol obtained from the same green coffee oil is equal to 43.5 and 30.072 g kg À 1 oil , respectively. Results are slightly higher compared to the ones obtained with the batch procedure. This can be explained by a better mixing of the coffee oil with the reagents and a faster transesterification reaction.
Journal of Chromatography A, 1988
ABSTRACT The following bonded silicas possessing alkyl and cyanoalkyl surface groups were synthes... more ABSTRACT The following bonded silicas possessing alkyl and cyanoalkyl surface groups were synthesized by reacting dimethylaminosilanes on silica: undecylsilica, 10:90, 30:70, 50:50, 70:30 and 90:10 undecyl—cyanodecylsilica and cyanodecylsilica. The multi-functional silicas were prepared with either a low or a high surface coverage. The physico-chemical properties of these silica-based mixed bonded phases were investigated with respect to surface ligand concentration (determined by elemental analysis, hydrofluoric acid attack and reflectance Fourier transform infrared spectroscopy), and textural properties, Vp and SBET (determined by the mercury intrusion method and the BET method, respectively).
Le Journal de Physique IV, 1991
Some anomalies observed in pulsed-laser thermal lens spectrophotometry are presented. Deviations ... more Some anomalies observed in pulsed-laser thermal lens spectrophotometry are presented. Deviations from the expected thermal lens signal were obtained with fluorescent as well as non-fluorescent compounds. ~l s o , transient absorption of the probe beam from long-lived triplet states may induce errors in the measurement of the true thermal lens signal.
Chemical Physics Letters, 1990
ABSTRACT Thermal-lens spectrophotometry has been used to determine fluorescence quantum yields. I... more ABSTRACT Thermal-lens spectrophotometry has been used to determine fluorescence quantum yields. It is shown that the method is not always accurate, especially in the case of dye molecules which exhibit high triplet-state quantum yields.
Applied Spectroscopy, 2001
This paper presents methods for measuring and modeling optical bleaching that occurs, by using co... more This paper presents methods for measuring and modeling optical bleaching that occurs, by using continuous laser sources for solution-phase organic dye molecule spectrometry. Photothermal lens experiments are used to measure the nonlinear optical absorption coef cients of eosin Y, erythrosin B, and pseudo-isocyanine iodide dyes in ethanol as a function of excitation irradiance. Excitation irradiance-dependent photothermal lens data are subsequently interpreted in terms of the photophysics and excited-state relaxation dynamics of the condensed-phase dye molecules under study. The model uses rst-order kinetics for excitation and subsequent metastable-state relaxation back to the ground state and accounts for both ground-and m etastable-state absorption. The measurem ent model accounts for thermal lens formation and apparatus con guration. Nonlinear absorption m easurem ents are t to the model with nonlinear regression. The resulting parameters allow calculation of triplet-state absorption coef cients and triplet to ground singlet state-relaxation rate constants.
Applied Optics, 1997
A simple method for calculating the effects of optical geometry on photothermal lens signals is s... more A simple method for calculating the effects of optical geometry on photothermal lens signals is shown. This method is based on calculating cumulative electric-field phase shifts produced by a series of Gaussian refractive-index perturbations produced by the photothermal effect. Theoretical results are found for both pulsed-laser and continuous Gaussian laser excitation sources and both single-and two-laser apparatuses commonly employed in photothermal lens spectroscopy. The effects of apparatus geometry on the resulting signal are shown. Analytical time-dependent signal results are found for small signals. Analytical pump-probe focus geometry results allow direct optimization for certain conditions. The calculations indicate that the photothermal lens signal is, in general, optimized for near-field detection-plane geometries.
Analytical Chemistry, 1995
Organic dye molecules having a finite triplet quantum yield are shown to yield anomalous photothe... more Organic dye molecules having a finite triplet quantum yield are shown to yield anomalous photothermal signals magnitudes when pulsed laser excitation is used. These anomalous signals can be due to optical bleaching of the electronic singlet states with subsequent optical absorption within the triplet spin state manifold. A model based on excitation and excited state relaxation rate expressions is derived and applied to the analysis of excitation laser irradiance-dependent photothermal signal magnitude data. The model is found to fit the experimental results very precisely. It is subsequently used to correct the photothermal signal at high irradiances and to deduce photodynamic parameters from the studied molecule. Regression of the model to the excitation irradiance-dependent data allows determination of the T2-->T1 relaxation rate constant and the triplet state cross absorption section. Model regression is applied to the analyses of erythrosin in water and ethanol solvent and of eosin and 1,1'-diethyl-2,2'-cyanine iodide dyes in ethanol solutions. A method for quantitative determination of analyte concentration is developed.
Analytica Chimica Acta, 1993
Optical Engineering, 1997
A model for photothermal lens signal generation in a cylindrical sample cell under constant irrad... more A model for photothermal lens signal generation in a cylindrical sample cell under constant irradiance excitation is described and tested. The model is developed with and without the assumption that the sample cell does not change temperature over the irradiation time. In both cases, the photothermal lens is predicted to be parabolic in form with a strength that is independent
European Journal of Organic Chemistry, 2015
ABSTRACT The first efficient synthesis of various 1,4-disubstituted pyrido[1′,2′:1,5]pyrazolo[3,4... more ABSTRACT The first efficient synthesis of various 1,4-disubstituted pyrido[1′,2′:1,5]pyrazolo[3,4-d]pyridazines is reported. The reactivity toward chlorine release at the C-1 and C-4 positions was investigated. SNAr and palladium-catalysed cross-coupling reactions were carried out, and conditions were optimised for each procedure. 1,4-Bis(het)aryl derivatives were obtained under a Suzuki cross-coupling procedure whereas SNAr substitution was achieved mainly at C-1 in preference to C-4. The monosubstituted C-4 morpholino derivative was used as a starting material to provide dissymmetrical 1,4-diaminated or 1-(het)aryl-4-morpholino products.
Talanta, 2013
Kahweol and cafestol are two diterpenes that exist mainly as esters of fatty acids in green coffe... more Kahweol and cafestol are two diterpenes that exist mainly as esters of fatty acids in green coffee oil. To recover them under their free form they have to be either saponified or trans-esterified. These two compounds are well known to be sensitive to heat, and reagents, therefore experimental conditions used in the transesterification reaction are critical. In this paper, a Doehlert experimental design plan is used to optimize the transesterification conditions using some key variables such as the temperature of the reaction, the reagent base concentration and the duration of the reaction. Therefore, the optimal parameters determined from the Doehlert design are equal to 70 1C, temperature of the reaction; 1.25 mol L À 1 concentration of the reagent base; and 60 min reaction time. The contour plots show that the extracted quantity of kahweol and cafestol can depend greatly from the experimental conditions. After transesterification, the free form of the diterpernes is extracted from the lipid fraction using liquidliquid extraction and analyzed using GC-FID without prior derivatization. The amount of kahweol and cafestol obtained from green coffee oil obtained by cold mechanical press of Catuai coffee bean is equal to 33.27 2.2 and 24.372.4 g kg À 1 oil, respectively. In an attempt to streamline the process, the transesterification reaction is performed in an in-flow chemistry reactor using the optimal conditions obtained with the Doehlert experimental design. The amount of kahweol and cafestol obtained from the same green coffee oil is equal to 43.5 and 30.072 g kg À 1 oil , respectively. Results are slightly higher compared to the ones obtained with the batch procedure. This can be explained by a better mixing of the coffee oil with the reagents and a faster transesterification reaction.
Journal of Chromatography A, 1988
ABSTRACT The following bonded silicas possessing alkyl and cyanoalkyl surface groups were synthes... more ABSTRACT The following bonded silicas possessing alkyl and cyanoalkyl surface groups were synthesized by reacting dimethylaminosilanes on silica: undecylsilica, 10:90, 30:70, 50:50, 70:30 and 90:10 undecyl—cyanodecylsilica and cyanodecylsilica. The multi-functional silicas were prepared with either a low or a high surface coverage. The physico-chemical properties of these silica-based mixed bonded phases were investigated with respect to surface ligand concentration (determined by elemental analysis, hydrofluoric acid attack and reflectance Fourier transform infrared spectroscopy), and textural properties, Vp and SBET (determined by the mercury intrusion method and the BET method, respectively).
Le Journal de Physique IV, 1991
Some anomalies observed in pulsed-laser thermal lens spectrophotometry are presented. Deviations ... more Some anomalies observed in pulsed-laser thermal lens spectrophotometry are presented. Deviations from the expected thermal lens signal were obtained with fluorescent as well as non-fluorescent compounds. ~l s o , transient absorption of the probe beam from long-lived triplet states may induce errors in the measurement of the true thermal lens signal.
Chemical Physics Letters, 1990
ABSTRACT Thermal-lens spectrophotometry has been used to determine fluorescence quantum yields. I... more ABSTRACT Thermal-lens spectrophotometry has been used to determine fluorescence quantum yields. It is shown that the method is not always accurate, especially in the case of dye molecules which exhibit high triplet-state quantum yields.
Applied Spectroscopy, 2001
This paper presents methods for measuring and modeling optical bleaching that occurs, by using co... more This paper presents methods for measuring and modeling optical bleaching that occurs, by using continuous laser sources for solution-phase organic dye molecule spectrometry. Photothermal lens experiments are used to measure the nonlinear optical absorption coef cients of eosin Y, erythrosin B, and pseudo-isocyanine iodide dyes in ethanol as a function of excitation irradiance. Excitation irradiance-dependent photothermal lens data are subsequently interpreted in terms of the photophysics and excited-state relaxation dynamics of the condensed-phase dye molecules under study. The model uses rst-order kinetics for excitation and subsequent metastable-state relaxation back to the ground state and accounts for both ground-and m etastable-state absorption. The measurem ent model accounts for thermal lens formation and apparatus con guration. Nonlinear absorption m easurem ents are t to the model with nonlinear regression. The resulting parameters allow calculation of triplet-state absorption coef cients and triplet to ground singlet state-relaxation rate constants.
Applied Optics, 1997
A simple method for calculating the effects of optical geometry on photothermal lens signals is s... more A simple method for calculating the effects of optical geometry on photothermal lens signals is shown. This method is based on calculating cumulative electric-field phase shifts produced by a series of Gaussian refractive-index perturbations produced by the photothermal effect. Theoretical results are found for both pulsed-laser and continuous Gaussian laser excitation sources and both single-and two-laser apparatuses commonly employed in photothermal lens spectroscopy. The effects of apparatus geometry on the resulting signal are shown. Analytical time-dependent signal results are found for small signals. Analytical pump-probe focus geometry results allow direct optimization for certain conditions. The calculations indicate that the photothermal lens signal is, in general, optimized for near-field detection-plane geometries.
Analytical Chemistry, 1995
Organic dye molecules having a finite triplet quantum yield are shown to yield anomalous photothe... more Organic dye molecules having a finite triplet quantum yield are shown to yield anomalous photothermal signals magnitudes when pulsed laser excitation is used. These anomalous signals can be due to optical bleaching of the electronic singlet states with subsequent optical absorption within the triplet spin state manifold. A model based on excitation and excited state relaxation rate expressions is derived and applied to the analysis of excitation laser irradiance-dependent photothermal signal magnitude data. The model is found to fit the experimental results very precisely. It is subsequently used to correct the photothermal signal at high irradiances and to deduce photodynamic parameters from the studied molecule. Regression of the model to the excitation irradiance-dependent data allows determination of the T2-->T1 relaxation rate constant and the triplet state cross absorption section. Model regression is applied to the analyses of erythrosin in water and ethanol solvent and of eosin and 1,1'-diethyl-2,2'-cyanine iodide dyes in ethanol solutions. A method for quantitative determination of analyte concentration is developed.
Analytica Chimica Acta, 1993
Optical Engineering, 1997
A model for photothermal lens signal generation in a cylindrical sample cell under constant irrad... more A model for photothermal lens signal generation in a cylindrical sample cell under constant irradiance excitation is described and tested. The model is developed with and without the assumption that the sample cell does not change temperature over the irradiation time. In both cases, the photothermal lens is predicted to be parabolic in form with a strength that is independent