• Bulletin of the Korean Chemical Society
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• v.19 no.9
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• pp.980-985
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• 1998

The excited-state intramolecular proton transfer (ESIPT) emission has been observed for 0.01 mM p-aminosalicylic acid (AS) in nonpolar aprotic solvents as demonstrated by the large Stokes' shifted fluorescence emission around 440 nm in addition to the normal emission at 330 nm. However in aprotic polar solvent such as acetonitrile, the large Stokes' shifted emission band becomes broadened, indicating existence of another emission band originated from intramolecular charge transfer (ICT). It is noteworthy that in protic solvents such as methanol and ethanol the normal and ICT emissions are quenched as the AS concentration decreases, followed by the appearance of new emission at 380 nm. These results are interpreted in terms of ESIPT coupled charge transfer in AS. Being consistent with these steady-state spectroscopic results, the picosecond time-resolved fluorescence study unravelled the decay dynamics of the ESIPT and ICT state ca. 300 ps and ca. 150 ps, respectively with ca. 40 ps for the relaxation time to form the ICT state.

• Membrane Journal
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• v.28 no.5
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• pp.326-331
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• 2018

Crosslinking of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) anion exchange membranes, which can be used for capacitive deionization (CDI), was investigated. PPO Anion exchange polymer was prepared through bromination and amination reaction steps and crosslinked with bisphenol A diglycidylether (BADGE), m-phenylenediamine (m-PDA), and hexamethylenediamine (HMDA). The gelation time by crosslinking was short in the order of HMDA > m-PDA > BADGE. The anion exchange membranes crosslinked at room temperature over a certain amount of crosslinking agent did not dissolve in an aprotic solvent such as 1-methylpyrrolidone (NMP) and the chemical durability of their membranes to organic solvent increased. The ion exchange capacity and water uptake of anion exchange membranes crosslinked with different crosslinker (BADGE) contents were measured and compared. The CDI performance of the crosslinked PPO anion exchange membrane immersed in the HMDA solution was almost the same as that of the non - crosslinked membrane except for the initial stage of the adsorption step.

• Archives of Pharmacal Research
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• v.5 no.2
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• pp.97-101
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• 1982

Depending upon the results obtained by the bromolactonization of olefinic acids (9-11) by means of N-bromosaccharin (4), the influence of the stabilities of the imidic anions resulted from heterolytic cleavage of N-haloimides, such as N-bromosuccinimide (1), N-bromophthalimde (2), and N-bromosaccharin (3) in dry N, N-dimethylformamide on the reactivity is elucidated.

• Journal of the Korean Chemical Society
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• v.13 no.2
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• pp.115-120
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• 1969

Kinetics of reactions of halide ions with 1-naphthyl methyl halide have been investigated in anhydrous acetone. Semi-quantitative analysis of the results shows that if the softness of the substrate increases remarkably, the nucleophilicity order of halide ions is $I^- > Br^- > Cl^-$ even in dipolar aprotic solvent. But for 1-naphthyl methyl bromide, though the reaction center which was made soft by symbiosis of bromine atom raises the reactivity of soft nucleophile, nucleophilicity order indicates that soft-soft interaction is interfered by perihydrogen.

• Membrane Journal
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• v.25 no.1
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• pp.32-41
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• 2015

High performance polysulfone microfiltration membranes with a high were successfully prepared by vapor induced phase separation (VIPS) coupled with non-solvent induced phase separation (NIPS) process. Asymmetric Membranes were prepared with PSF/DMF/PVP/PEG/DMSO/water mixed solutions and water/IPA coagulant. PSF, DMF, PVP, PEG, DMSO, water was used as a membrane polymer, a solvent, a hydrophilic polymer additive, a polar protic liquid polymer, a polar aprotic nonsolvent, and a polar protic nonsolvent in the casting solution, respectively. The addition of polar aprotic nonsolvents, and polar protic nonsolvents is a convenient and effective method to control membrane structure. In order to control the morphology of polymeric membranes, the spontaneous emulsification induced by drawing water vapor into the exposed casting solution surface has been used. Control of the internal morphology of polymeric membranes by using mixed coagulation solution such as water and IPA is discussed in the present work. The pure water permeability, pore size distribution, surface hydrophilicity and membrane morphology were investigated. Due to the addition of DMSO to casting solution, the mean pore size increased almost $0.2{\mu}m$ and the water flux increased about 1000-1800 LMH.

• Journal of the Korean Chemical Society
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• v.40 no.1
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• pp.65-71
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• 1996

The chemical behaviour of the Eu(Ⅲ) complexes with organic ligands(tris[3-(trifluoromethylhydroxymethylene-camphorato)]) and tris[3-heptafluoropropylhydroxymethylene-camphorato)] has been investigated by the UV/vis-spectrophotometric, magnetic, and electrochemcial methods. The two or three energy absorption bands are observed by the spectra of these complexes. The magnitude of crystal field splitting energy, the spin pair energy and strength were obtained from the spectra of the complexes. These complexes are found to be delocalization, low-spin state, and strong bonding strenth of electron configuration. The magnetic dipolemoment are found to be diamagnetic. The redox reaction processes of complexes were investigated by cyclic voltammetry in aprotic solvent. The redox reaction processes of complexes are turned out to be single or double reaction with respect to one electron diffusion current.

• Journal of the Korean Chemical Society
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• v.40 no.10
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• pp.649-655
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• 1996

The chemical behaviour of Pt(Ⅱ) and Pd(Ⅱ) complexes with the organic ligand tetramethylenesulfoxide(TMSO) has been investigated by UV/vis-spectrophotometric, magnetic, and electrochemical methods. Two energy absorption bands are observed in the spectra of these complexes. The crystal field splitting energy, spin pairing energy, and bond strength were obtained from the spectra of the complexes. The electronic properties of the complexes are found to be delocalized, and low-spin state. The correlation between ligand and metals were strong bonding strength. These complexes are diamagnetics. The redox reaction processes of the complexes were investigated by cyclic voltammetry in an aprotic solvent. The redox processes of complexes turned out to be respect to one-electrton one step. These complexes were considerably diffusion and reaction controlled.

• Journal of the Korean Chemical Society
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• v.41 no.2
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• pp.63-68
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• 1997

Calorimetric measurements have been carried out for the binary mixture between protic, ROH (R=Me, Et) and dipolar aprotic solvents, MeCN,$Me_2CO,\;MeNO_2(or EtNO_2)$in order to investigate the molecular interaction and liquid structure of isodielectric solvents. From the measured partial molar enthalpies of the solutions, excess enthalpies for the mixing process were determined. The hydrogen bond strength between two components decreases in the order of$ROH-ROH>ROH-Me_2CO>ROH-MeCN>ROH-MeNO_2(or EtNO_2)$and the hydrogen bond donor acidity decreases in the order of MeOH>EtOH. From this result, we can conclude that the most important interaction for the formation of binary liquid mixture comes from the specific hydrogen bond.

• Analytical Science and Technology
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• v.22 no.2
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• pp.159-165
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• 2009

The thermochromism of fluoran has been examined. The DCF exists as a colorless lactone in aprotic solvents. However, the DCF exists in the form of an equilibrium mixture of a colored zwitter-ion and a colorless lactone in protic solvents. When an acid is added to the solution, the DCF exists an equilibrium mixture as a colorless lactone and a colored cation even in aprotic solvents. In order to understand the interaction between the DCF and the solvent, absorption spectra of the DCF in various solvents were measured. The thermodynamic parameters of the DCF have also been investigated. From the variation of absorbance with temperature, the standard enthalpy changes ${\Delta}H^0$ of the equilibrium between the lactone and the zwitter-ion in various solvents have been determined. The standard enthalpy change ${\Delta}H^0$ is approximately -2.0 kJ/mol in protic solvents. In acidic solution, the standard enthalpy change is measured to be to zero in protic solvents within the experimental error. When the carboxylic group is protonated in acidic solution, a poor interaction between the dye and the solvent is expected.

• Journal of the Korean Chemical Society
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• v.24 no.1
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• pp.8-14
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• 1980

Solvolysis rate constants for methylchloroformate, $CH_3O$(CO)Cl, methylthiono-chloroformate, $CH_3O$(CS)Cl, and methylthiolchloroformate, $CH_3S$(CO)Cl, have been determined conductometrically in acetone-water and acetonitrile-water mixtures, and activation parameters, ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$, have been derived. Results show that in water-rich regions the order of rate increases as $$CH_3O(CO)Cl while in dipolar aprotic solvent-rich region this order reverses. The plots of log k vs. solvent parameters, Y, $\frac{D-1}{2D+1}$ and log($H_2$) show that the order of rate increase in water-rich region is the results of increase in $S_N1$ character. It is concluded that $CH_3S$(CO)Cl solvolyzes via $S_N1$ mechanism whereas $CH_3O$(CO)Cl reacts via $S_N2$ and $CH_3O$(CS)Cl via intermediate mechanism in water-rich region.