• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.55-59
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• 2003

This work is focused on analyzing ion-pair interactions and showing the effect of solvent induced inter-atomic attractions in various dielectric environments. To estimate the stability of ion-pairs, SCI-PCM ab initio MO calculations were carried out. We show that the solvent-induced attraction or ‘cavitation' energy of the ion-pair interactions in solution that arises mainly from the stabilization of the water molecules by the generation of an electrostatic field. In fact, even the strong electrostatic interaction characteristic of ion-pair interactions in the gas phase cannot overcome the destabilization or reorganization of the water molecules around solute cavities that arise from cancellation of the electrostatic field. The solvent environment, possibly supplemented by some specific solvent molecules, may help place the solute molecule in a cavity whose surroundings are characterized by an infinite polarizable dielectric medium. This behavior suggests that hydrophobic residues at a protein surface could easily contact the side chains of other nearby residues through the solvent environment, instead of by direct intra-molecular interactions.

• Bulletin of the Korean Chemical Society
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• v.21 no.3
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• pp.351-352
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• 2000

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.682-685
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• 1996

Photothermal properties depend on the characteristics of energy transfer processes in solution. In this study, a time-resolved single beam thermal lens experiment in various solvents is employed to investigate the energy coupling effects which govern the energy transfer processes. Interestingly, it is observed that the behaviour of the photothermal propagation in solution depends on the property of solution and the concentration of solute in a single beam thermal lens configuration. These characteristics lead us to consider the solute-solvent coupling effects as well as the solvent-solvent interactions.

• Archives of Pharmacal Research
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• v.12 no.1
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• pp.58-61
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• 1989

Studies of selectivity of hydrogen bond formation in chiral solute-solvent systems have been performed by $^1H\;and\;^{13}C$ nuclear magnetic resonance techniques. These data are correlated with the results of gas chromatographic investigations of the same systems. Interactions between the optically active solvent(N-(N-benzoyl-L-amino acid)-anilide) and optically active solute (N-trifluoroacetyl -L-alanyl isopropyl ester) were examined. NMR evidence indicated that hydrogen bonding interaction occurred between two N-H portion and on peptidyl carbonyl portion in stationary phase and solute molecule on three points. The association constants of solvent-solute interaction were calculated and the structure of the diastereomeric association complex between N-(N-benzoyl-L-valyl)-anilide and N-TFA-L-alanyl isopropyl ester was proposed.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.610-616
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• 2014

The influence of solvent polarity on the absorption spectra of some synthesized azo dye with heterocyclic moieties and ${\beta}$-naphthol (1-3) have been investigated using a UV-Visible spectrophotometer. The spectral characteristics of the azo dyes (1-3) in different solvents at room temperature were analyzed. The solvatochromic empirical variables like ${\pi}^*$, ${\alpha}$, and ${\beta}$ have been used to discuss the solvatochromic behaviour of the dyes and to evaluate their contributions to the solute-solvent interactions. A multi-parameter regression model for quantitative assessment of the solute/solvent interaction and the absorption has been used to explain the solvent effect on azo dyes (1-3).

• Journal of Photoscience
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• v.12 no.2
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• pp.57-61
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• 2005

The ground and excited state dipole moments of Coumarin 450 (C 450) laser dye were measured at room temperature in several solvents of varying dipole moments. The ground state dipole moment (${\mu}_g$) is estimated by using the modified Onsagar model and the excited state dipole moments (${\mu}_e$) were estimated by the method of solvatochromism as well as by utilizing the microscopic solvent polarity parameter ($E^N_T$). Further, the deviation of some of the points from the linearity of the $E^N_T$ versus Stokes shift indicates the existence of specific type of solute-solvent interaction. The excited state dipole moment of C 450 were found to be higher than those of the ground state and is interpreted in terms of the resonance structure of the molecule. A reasonable agreement has been observed between the values obtained by the method of solvatochromism and modified Onsagar model. It is observed that, corresponding to cyclohexane solution, the fluorescence maxima shift towards the red region with increasing the polarity of the solvents, hence the transition involved are of ${\pi}-{\pi}^*$ type.

• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.105-109
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• 2000

High-performance liquid chromatography is suitable for getting thermodynamic information about solute-solvent interactions. We used a squalane impregnated $C_{18}$ phase as a presumably bulk-like stationary phase to secure a simple partition mechanism for solute retention in reversed phase liquid chromatographic system. We measured retention data of some selected solutes (benzene, toluene, ethylbenzene, propylbenzene, butylbenzene, phenol, benzylalcohol, phenethylalcohol, benzylacetone, acetophenone, benzonitrile, benzylcyanide) at 25, 30, 35, 40, 45, and 50 $^{\circ}C$ in 30/70, 40/60, 50/50, 60/40 and 70/30 (v/v%) acetonitrile/water eluents. The van't Hoff plots were nicely linear, thus we calculated dependable thermodynamic values such as enthalpies and entropies of solute transfer from the mobile phase to the stationary phase based on more than four retention measurements on different days (or weeks). We found that the cavity formation effect was the major factor in solute distribution between the mobile and stationary phases in the system studied here. Our data were com-pared with some relevant literature data.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1752-1756
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• 2006

This study explores and interprets in a new way the complex solvent and the temperature dependence of the NMR shifts for the N-$CH_2$ protons in tris(N,N-diethyldithiocarbamato) iron(III) in acetone, benzene, carbon disulfide, chloroform, dimethylformamide and pyridine. The NMR shifts are interpreted in terms of the Fermi contact interaction and the dipolar term from the multipole expansion of the interaction of the electron orbital angular momentum and the electron spin dipolar-nuclear spin angular momentum. This analysis yields a direct measure of the effect of the solvent system on the environment of the transition metal ion. The results are analysed in terms of the crystal field environment of the transition metal ion with contributions from (a) the dithiocarbamate ligand (b) the solvent molecules and (c) the interaction of the effective dipole moment of the polar solvent molecule with the transition metal ion complex.

• Journal of the Korean Chemical Society
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• v.60 no.2
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• pp.111-117
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• 2016

In this article, new Gibbs free energy of mixing is derived when there are specific interactions between solvent-solute molecules and between solute-solute molecules in binary solutions. It is asssumed that a probability of specific interactions satisfies a binomial distribution. Using this Gibbs free energy of mixing, we investigate possible types of partial miscibilities and show that Ω-shaped temperature-composition phase diagrams can exist. We calculate Ω-shaped temperature-composition phase diagram of water-2-butanol system and compare that with result calculated by the method of Hino⁵ et al. and the experimental data.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.65-70
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• 2002

We have evaluated the specific hydroxyl group-solvent and carbonyl group-solvent interactions by using an Alltima C18 stationary phase and by measuring the retention data of carefully selected solutes in 60/40, 70/30, and 80/20(v/v%) acetonitrile/water eluents at 25, 30, 35, 40, 45, and 50 oC. The selected solutes are phenol, acetophenone, alkylbenznes(benzene to hexylbenznene), 4 positional isomers of phenylbutanol, 5-phenyl-1-pentanol, 3 positional isomers of alkylarylketone derived from butylbenzene, and 1-phenyl-2-hexanone. The magnitudes of hydroxyl group-acetonitrile/water specific interaction enthalpies are larger than those of carbonyl group-acetonitrile/water specific interaction enthalpies in general while the magnitudes of carbonyl group-methanol/water specific interaction enthalpies are larger than those of hydroxyl group-methanol/water specific interactions. We observed clear discrepancies in functional group-solvent specific interaction among positional isomers. The variation trends of solute transfer enthalpies and entropies with mobile phase composition in the acetonitrile/water system are much different from those in the methanol/water system. The well-known pocket formation of acetonitrile in aqueous acetonitrile mixtures has proven to be useful to explain such phenomena.