Local density augmentation around acetophenone N,N,N′,N′-tetramethylbenzidine exciplex in supercritical water

Aizawa, Takafumi; Kanakubo, Mitsuhiro; Ikushima, Yutaka; Smith, Richard L.; Saitoh, Tohru; Sugimoto, Nobuhiro

doi:10.1016/j.cplett.2004.05.100

Cited by 14 publications

(13 citation statements)

References 15 publications

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“…The local solvation structure and especially the local density augmentation (LDA) effects of several, mainly dilute, supercritical solutions have been investigated by employing experimental techniques, − statistical mechanical theories − and molecular simulations. − These studies have revealed important information about the solvation in SCFs.…”

Section: Introductionmentioning

confidence: 99%

Solvation Structure and Dynamics of cis- and trans-1,2 Dichloroethene Isomers in Supercritical Carbon Dioxide. A Molecular Dynamics Simulation Study.

2011

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Molecular dynamics simulation techniques have been employed to investigate the solvation structure and dynamics in dilute mixtures of cis- and trans-1,2-dichloroethene in supercritical carbon dioxide. The calculations were performed for state points along a near-critical isotherm (1.02 T(c)) over a wide range of densities, using new developed optimized potential models for both isomers. The similarities and differences in the solvation structures around each isomer have been presented and discussed. The local density augmentation and enhancement factors of CO(2) around the isomers have been found significantly larger than the corresponding values for pure supercritical CO(2). The dynamic local density reorganization has been investigated and related to previously proposed relaxation mechanisms. The density dependence of the calculated self-diffusion coefficients has revealed the existence of a plateau in the region of 0.7-1.1 ρ(c), where the local density augmentation exhibits the maximum value. The reorientational dynamics of the C═C bond vector have been also studied, exhibiting significant differences between the two isomers in the case of the second-order Legendre time correlation functions.

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Section: Introductionmentioning

confidence: 99%

Solvation Structure and Dynamics of cis- and trans-1,2 Dichloroethene Isomers in Supercritical Carbon Dioxide. A Molecular Dynamics Simulation Study.

2011

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“…In the case of attractive solutes diluted in sc solvents, spectroscopic studies show average local density enhancement that is two to five times the bulk one. [7][8][9][10][11][12] Results have been also obtained from computer simulations ͑CSs͒ employed to model dilute solutions near the critical point. 7,[12][13][14][15][16][17][18] According to the recent literature on the field, the local density augmentation in some nonpolar neat scfs, such as methane, ethane, CO 2 , and C 6 F 6 , has been investigated by a number of authors using vibra-tional spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Local density augmentation and dynamic properties of hydrogen-and non-hydrogen-bonded supercritical fluids: A molecular dynamics study

Skarmoutsos

Samios

2007

The Journal of Chemical Physics

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The local density inhomogeneities in neat supercritical fluids were investigated via canonical molecular dynamics simulations. The selected systems under investigation were the polar and hydrogen-bonded fluid methanol as well as the quadrupolar non-hydrogen-bonded carbon dioxide one. Effective local densities, local density augmentation, and enhancement factors were calculated at state points along an isotherm close to the critical temperature of each system (T(r)=1.03). The results obtained reveal strong influence of the polarity and hydrogen bonding upon the intensity of the local density augmentation. It is found that this effect is sufficiently larger in the case of the polar and associated methanol in comparison to those predicted for carbon dioxide. For both fluids the local density augmentation values are maximized in the bulk density region near 0.7rho(c), a result that is in agreement with experiment. In addition, the local density dynamics of each fluid were investigated in terms of the appropriate time correlation functions. The behavior of these functions reveals that the bulk density dependence of the local density reorganization times is very sensitive to the specific intermolecular interactions and to the size of the local region. Also, the estimated local density reorganization time as a function of bulk density of each fluid was further analyzed and successfully related to two different time-scale relaxation mechanisms. Finally, the results obtained indicate a possible relationship between the single-molecule reorientational dynamics and the local density reorganization ones.

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“…A cross-sectional diagram of the high-temperature high-pressure optical cell is shown in Figure . The cell was custom designed for the experiments considered in this work and consisted of antisymmetrically placed windows, commercially available high-temperature seals (Taiatsu Techno, TTS seal, Tokyo), and a double-window system that used sapphire and quartz as described in our previous paper . One port of the cell was connected to a nitrogen gas cylinder, and the other port was connected to a back-pressure regulator.…”

Section: Methodsmentioning

confidence: 99%

“…Since the characteristics of the short-lived species, such as reaction intermediates, are key to elucidating the underlying chemical reaction mechanisms, evaluation of local density augmentation around short-lived species should be important in processes such as formation of radicals, ionic species, or molecular rearrangements. In a previous study, we determined the local density augmentation around exciplex, a short-lived species, in supercritical water at a constant temperature of 380 °C and found that local density augmentation exists in the low-pressure (6−25 MPa) region. The temperature dependence of local density augmentation around exciplex needs to be clarified as the next step in our investigation.…”

Section: Introductionmentioning

confidence: 99%

Temperature Dependence of Local Density Augmentation for Acetophenone N,N,N‘,N‘-Tetramethylbenzidine Exciplex in Supercritical Water

et al. 2005

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Local density augmentation around exciplex between acetophenone and N,N,N',N'-tetramethylbenzidine in supercritical water was measured by observing the peak shift of transient absorption spectrum at temperatures from 380 to 410 degrees C and at pressures from 6 to 37 MPa. Large local density augmentation was observed at lower solvent densities. Local density augmentation was evaluated by the excess density, which was defined as the difference between local density and bulk density, and the density enhancement factor, which was defined by the ratio of the local density to the bulk density. The number of solvating molecules was estimated with a Langmuir adsorption model. The excess density was found to exhibit a maximum at approximately 0.15 g cm(-3), which decreased with increasing temperature. The density enhancement factor was found to decrease with increasing temperature; however, its value was much greater than unity at 410 degrees C, which provides evidence that exciplex-water interactions still exist at these conditions. The temperature dependence of local density augmentation around the exciplex in supercritical water was comparable with that in supercritical carbon dioxide, which suggests that the ratios of the solute-solvent and solvent-solvent interactions are comparable between these two systems.

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Local density augmentation around acetophenone N,N,N′,N′-tetramethylbenzidine exciplex in supercritical water

Cited by 14 publications

References 15 publications

Solvation Structure and Dynamics of cis- and trans-1,2 Dichloroethene Isomers in Supercritical Carbon Dioxide. A Molecular Dynamics Simulation Study.

Solvation Structure and Dynamics of cis- and trans-1,2 Dichloroethene Isomers in Supercritical Carbon Dioxide. A Molecular Dynamics Simulation Study.

Local density augmentation and dynamic properties of hydrogen-and non-hydrogen-bonded supercritical fluids: A molecular dynamics study

Temperature Dependence of Local Density Augmentation for Acetophenone N,N,N‘,N‘-Tetramethylbenzidine Exciplex in Supercritical Water

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