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Jed Patrick Montero Catalan - One of the best experts on this subject based on the ideXlab platform.
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on the solvatochromism of the n π electronic transitions in ketones
Physical Chemistry Chemical Physics, 2011Co-Authors: Javier Catalán, Jed Patrick Montero CatalanAbstract:The solvatochromism of the n ↔ π* electronic transitions of acetone, which is determined in this work by means of absorption and emission spectroscopy, has been studied using the Pure Solvent scales for polarizability, dipolarity and acidity of the medium. From these analyses, the necessary reduction of the dipole moment and the increase of the polarizability for acetone on electronic excitation are evaluated using Abe's approach (Bull. Chem. Soc. Jpn. 1966, 39, 936). The influence that the increase of the aromatic structure (cf.acetophenone) and the lengthening of the size of the alkyl substituents R– (cf. R–CO–R) cause on the solvatochromism of acetone is discussed. Also, we have shown that the photophysical model proposed by Pimentel (J. Am. Chem. Soc. 1957, 79, 3323), which is widely accepted for explaining the n → π* blue shift phenomenon for hydrogen-bonded complexes, is mistaken due to ignoring the acid–base changes undergone on electronic excitation; accordingly, a new photophysical model has been proposed.
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On the solvatochromism of the n ↔ π* electronic transitions in ketones
Physical Chemistry Chemical Physics, 2011Co-Authors: Javier Catalán, Jed Patrick Montero CatalanAbstract:The solvatochromism of the n ↔ π* electronic transitions of acetone, which is determined in this work by means of absorption and emission spectroscopy, has been studied using the Pure Solvent scales for polarizability, dipolarity and acidity of the medium. From these analyses, the necessary reduction of the dipole moment and the increase of the polarizability for acetone on electronic excitation are evaluated using Abe's approach (Bull. Chem. Soc. Jpn. 1966, 39, 936). The influence that the increase of the aromatic structure (cf.acetophenone) and the lengthening of the size of the alkyl substituents R– (cf. R–CO–R) cause on the solvatochromism of acetone is discussed. Also, we have shown that the photophysical model proposed by Pimentel (J. Am. Chem. Soc. 1957, 79, 3323), which is widely accepted for explaining the n → π* blue shift phenomenon for hydrogen-bonded complexes, is mistaken due to ignoring the acid–base changes undergone on electronic excitation; accordingly, a new photophysical model has been proposed.
Javier Catalán - One of the best experts on this subject based on the ideXlab platform.
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analysis of the solvatochromism of 9 9 biaryl compounds using a Pure Solvent dipolarity scale
Journal of Physical Chemistry A, 2012Co-Authors: Javier Catalán, Christian ReichardtAbstract:The UV/vis absorption and fluorescence spectra of 9,9′-bisanthracenyl (BA), 9,9′- bisacridinyl (BAC), 9,9′-bicarbazyl (BC), and 9-(9′-anthracenyl)carbazole (C9A) were precisely recorded in Solvents that change their Solvent dipolarity scale (SdP) values from 0.000 (in 2-methylbutane at 293 K) to 1.294 (in 1-chlorobutane at 77 K). An analysis based (i) on the solvatochromic behavior of the four 9,9′-biaryl compounds in terms of the dipolarity of the Solvents used, quantified by means of their SdP values, and (ii) on the behavior of the emission band profiles, allows the conclusion that, whereas the apolar 9,9′-biaryl compounds BA, BAC, and BC need Solvents with SdP values larger than 0.74 to give a twisted intramolecular charge-transfer (TICT) process after excitation, for dipolar C9A the TICT mechanism is predominant already at Solvent SdP values smaller than 0.23, i.e., near a Solvent dipolarity of 0. The accuracy and simplicity achieved by application of the SdP scale in analyzing the solvatochromic beh...
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on the solvatochromism of the n π electronic transitions in ketones
Physical Chemistry Chemical Physics, 2011Co-Authors: Javier Catalán, Jed Patrick Montero CatalanAbstract:The solvatochromism of the n ↔ π* electronic transitions of acetone, which is determined in this work by means of absorption and emission spectroscopy, has been studied using the Pure Solvent scales for polarizability, dipolarity and acidity of the medium. From these analyses, the necessary reduction of the dipole moment and the increase of the polarizability for acetone on electronic excitation are evaluated using Abe's approach (Bull. Chem. Soc. Jpn. 1966, 39, 936). The influence that the increase of the aromatic structure (cf.acetophenone) and the lengthening of the size of the alkyl substituents R– (cf. R–CO–R) cause on the solvatochromism of acetone is discussed. Also, we have shown that the photophysical model proposed by Pimentel (J. Am. Chem. Soc. 1957, 79, 3323), which is widely accepted for explaining the n → π* blue shift phenomenon for hydrogen-bonded complexes, is mistaken due to ignoring the acid–base changes undergone on electronic excitation; accordingly, a new photophysical model has been proposed.
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On the solvatochromism of the n ↔ π* electronic transitions in ketones
Physical Chemistry Chemical Physics, 2011Co-Authors: Javier Catalán, Jed Patrick Montero CatalanAbstract:The solvatochromism of the n ↔ π* electronic transitions of acetone, which is determined in this work by means of absorption and emission spectroscopy, has been studied using the Pure Solvent scales for polarizability, dipolarity and acidity of the medium. From these analyses, the necessary reduction of the dipole moment and the increase of the polarizability for acetone on electronic excitation are evaluated using Abe's approach (Bull. Chem. Soc. Jpn. 1966, 39, 936). The influence that the increase of the aromatic structure (cf.acetophenone) and the lengthening of the size of the alkyl substituents R– (cf. R–CO–R) cause on the solvatochromism of acetone is discussed. Also, we have shown that the photophysical model proposed by Pimentel (J. Am. Chem. Soc. 1957, 79, 3323), which is widely accepted for explaining the n → π* blue shift phenomenon for hydrogen-bonded complexes, is mistaken due to ignoring the acid–base changes undergone on electronic excitation; accordingly, a new photophysical model has been proposed.
W. Borchard - One of the best experts on this subject based on the ideXlab platform.
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Theory of swelling of a crosslinked substance in equilibrium with a Pure Solvent in various phases. Part II: The variation of the pressure
Colloid and Polymer Science, 1993Co-Authors: W. BorchardAbstract:A theory of swelling is presented which describes the equilibrium swelling of a body in a Solvent in its various states. The pressure dependence of the pressure-concentration swelling curves is treated for the swelling agent occurring in the liquid, crystalline or vapor phase. The slopes of the pressureconcentration swelling curves are dependent on the differential volume of dilution of the Solvent and, additionally, on the volume changes of vaporization, crystallization, and sublimation of the Solvent corresponding to the state of the swelling agent. At the melting and boiling pressure of the swelling agent the swelling curves change their slopes with a discontinuity, which is most distinct at the evaporation transition. By measurements of the slopes of the swelling curves at the transition pressure the derivative ∂μ_1/∂w_1 at constant temperature and pressure, which is the change of the chemical potential of the Solvent with its weight fraction, is obtained. Thus, a further equation is given to test statistical theories at the transition pressures. Simultaneous variations of the swelling with changes of temperature are also treated.
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Phase equilibria in polymer/Solvent systems. Part V: Thermodynamic theory of the swelling pressure equilibrium of a crosslinked substance with a Solvent in various phases
Colloid and Polymer Science, 1993Co-Authors: W. BorchardAbstract:A thermodynamic theory has been developed to define the swelling pressure equilibrium between a homogeneous gel and a Pure Solvent, where phase transitions of the Solvent, such as evaporation and crystallization can occur. It is shown that the equilibrium curve, which describes the temperature dependence of the composition in the gel phase under the condition of a constant swelling pressure, has distinct bends at the transition temperatures. These bends are related to the enthalpies of transition of the Pure Solvent at the transition temperatures. As a consequence of the phase transition of the Solvent the swelling pressure-temperature curve at constant composition of the gel shows a discontinuous behavior at the transition point. Numerical calculations with a modified Flory-Huggins expression, based on results of swelling and deswelling measurements of the system crosslinked PEG/water, are presented. The discussion includes natural systems, which are in the gel state, where water may crystallize in the extracellular space.
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Phase equilibria in polymer/Solvent systems. Part V: Thermodynamic theory of the swelling pressure equilibrium of a crosslinked substance with a Solvent in various phases
Colloid and Polymer Science, 1993Co-Authors: W. BorchardAbstract:A thermodynamic theory has been developed to define the swelling pressure equilibrium between a homogeneous gel and a Pure Solvent, where phase transitions of the Solvent, such as evaporation and crystallization can occur. It is shown that the equilibrium curve, which describes the temperature dependence of the composition in the gel phase under the condition of a constant swelling pressure, has distinct bends at the transition temperatures. These bends are related to the enthalpies of transition of the Pure Solvent at the transition temperatures. As a consequence of the phase transition of the Solvent the swelling pressure-temperature curve at constant composition of the gel shows a discontinuous behavior at the transition point. Numerical calculations with a modified Flory-Huggins expression, based on results of swelling and deswelling measurements of the system crosslinked PEG/water, are presented. The discussion includes natural systems, which are in the gel state, where water may crystallize in the extracellular space.
Mireille Turmine - One of the best experts on this subject based on the ideXlab platform.
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Micellar aggregation for ionic surfactant in Pure Solvent and electrolyte solution: nonextensive thermodynamics approach.
Journal of colloid and interface science, 2008Co-Authors: Pierre Letellier, Alain Mayaffre, Mireille TurmineAbstract:Abstract We show in this study that the concepts of nonextensive thermodynamics introduced and applied in a series of previous studies can be used to describe the behaviour of ionic surfactant solutions at concentrations higher than the critical micelle concentration (cmc) in Pure Solvents and in the presence of electrolytes. We supposed that the aggregated amphiphiles and their counter ions form two interpenetrated nonextensive phases of the same thermodynamic dimension, m, characterised by two parameters A am and A CI related to the aggregated amphiphile and the counter ion, respectively. Our experimental results and those published in the literature indicate that logarithms of the activities of the amphiphile and of its counterion vary with the quantity of aggregated monomer according to a power law. Thus, we demonstrate a linear relation between the logarithms of the activities of the two ions beyond the cmc in Pure Solvents (“micellization product”). An original relation, different from the Corrin–Harkins relation, can thus be established to describe the effects of salt on the cmc of ionic surfactants. According to this relation the cmc of charged surfactant in some systems can increase in the presence of an electrolyte with a common ion.
Laurent Bouteiller - One of the best experts on this subject based on the ideXlab platform.
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Isothermal Titration Calorimetry of Supramolecular Polymers
Langmuir, 2004Co-Authors: Alix Arnaud, Laurent BouteillerAbstract:A method to characterize the self-association of supramolecular polymers by isothermal titration calorimetry (ITC) has been designed. Association constants in the range 104to 106 dm3mol-1have been successfully determined from the heat exchange occurring when a supramolecular polymer solution is injected into a calorimetric cell containing Pure Solvent. Very good agreement with literature values has been obtained. Compared to other techniques (such as NMR or FTIRspectroscopy), the use of ITC presents several advantages: (i) the enthalpy of association is obtained together with the association constant from the same experiment, (ii) the measurements can be performed in almost any Solvent, and (iii) systems with higher association constants can be characterized.
