• Journal of the Korean Chemical Society
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• v.34 no.5
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• pp.438-444
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• 1990

Observed rate constants (k$_{obs.}$) for Hg$^{2+}$-catalysed aquation of cis-[Co(en)$_2$(OH$_2$)Cl]$^{2+}$, [Co(NH$_3$)$_5$Cl]$^{2+}$, cis-[Co(NH$_3$)$_4$(OH$_2$)Cl]$^{2+}$, and [Co(NH$_2$CH$_3$)$_5$Cl]$^{2+}$ were measured at various concentrations of Hg$^{2+}$. The k$_{obs.}$ was increased with increasing the concentrations of Hg$^{2+}$. The k$_{obs.}$ were related to mechanistically derived rate constants by the relationship; Rate = k$_2$K[complex][Hg$^{2+}$]. Various mixed aqueous-organic solvent have been successfully employed for Hg$^{2+}$-catalysed aquation of octahedral myetal complexes. From the slope of the plot of log k againt Y (solvent ionizing power), the mechanism on the aquation of Co(Ⅲ) complexes by Hg$^{2+}$ has been suggested to be I$_d$-mechanism. The change in a rate on aquation of each Co(Ⅲ) complex was related to the ligand field parameters (${\Delta}$), for Co(Ⅲ) complexes.

• Journal of the Semiconductor & Display Technology
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• v.15 no.2
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• pp.38-42
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• 2016

We investigate the solution coating process of organic small molecules that are easily recrystallized in a solvent. The spin-coated films of small molecule N,N'-diphenly-N,N'-bis(1,1'-biphenyl)-4,4'-diamine (NPB) exhibit many aggregations on the surface and thus poor surface morphology. To tackle it, we have added a chain-entangled polymer poly(N-vinylcarbazole) (PVK) into the NPB solution. It is found that a small amount of PVK indeed prohibits the recrystallization of NPB in a solvent. By the addition of PVK (30 wt%), the peak-to-peak roughness of the films is reduced from 262 nm down to 2.7 nm, which is even lower than that (~5.1 nm) of the polymer film. It is also demonstrated that OLED with the PVK-mixed NPB film shows higher current and power efficiencies, compared to OLED with the NPB or PVK film. It is attributed that the addition of PVK into NPB suppresses the occurrence of leaky channels induced by the recrystallization phenomenon.

• Analytical Science and Technology
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• v.15 no.2
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• pp.127-134
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• 2002

Analytical method to determine rare earth elements which were extracted to organic phase by inductively coupled plasma mass spectrometry(ICP-MS) was investigated. Organic phase which had extracted rare earth elements was directly aspirated into ICP-MS by ultrasonic nebulizer(USN) in order to reduce solvent load to the plasma. Then, the count rate increased when MIBK(methyl isobutyl ketone) was added to EtOH(ethanol) but decreased when 0.03 M HEH(2-ethylhexyl-2-ethylhexyl phosphonic acid, $P_{507}$, PC88A) was added to solvent which mixed MIBK with EtOH. The optimal temperatures of desolvation system were -10 $^{\circ}C$ for the condenser and 150 $^{\circ}C$ for the heating tube. The optimal nebulizer flow rate which gave maximum count rate and minimum reflect power was 0.7 L/min. The optimal pH and extraction time were 4.3 and 10 min for MIBK-0.03 M HEH system. Detection limits which were obtained through calibration curves at the range of 0.2 ${\sim}$ 20 ng/mL were 0.02 ${\sim}$ 0.05 ng/mL under the optimal experimental conditions.

• Journal of the Korean Chemical Society
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• v.10 no.3
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• pp.114-118
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• 1966

The glass electrode was empirically calibrated in dioxane-and ethanol-water mixed solvents, by means of which the pH-meter reading could be converted to stoichiometric hydrogen ion concentration. By the potentiometric titration method, the thermodynamic dissociation constants of hydrogen cupferrate (HCup) with variations of ionic concentration in aqueous solution were determined, and by the extrapolation of the constants the new thermodynamic $pK_a$ value, 3.980${\pm}$0.006, at zero ional concentration was obtained. The thermodynamic dissociation constants of HCup in dioxane-and ethanol-water solution were also potentiometrically determined with the changes in composition of organic solvents at 0.01 and 0.05 of the ionic strength(${mu}$) and 25 $^{\circ}C$. The empirical formula of the constants with mole fraction(n) of the organic solvent are as follow: Dioxane-water solution. $pK_a$= 12.96n + 4.10 at ${\mu}$ = 0.01, n = 0.0228∼0.171 $pK_a$= 12.05n + 4.23 at ${\mu}$ = 0.05, n= 0.0228∼0.171 Ethanol-water solution, $pK_a$= 4.0ln + 4.26 at ${\mu}$= 0.01, n= 0.0395∼0.262 $pK_a$= 3.83n + 4.34 at ${\mu}$= 0.05, n= 0.0395∼0.262

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.211-220
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• 2013

The characteristic fluorescence properties of quercetin (QCT) and apigenin (API) were studied in various $CH_3OH-H_2O$ and $CH_3CN-H_2O$ mixed solvents. The structure of QCT is completely planar. API is not planar at the ground state but becomes nearly planar at the excited state. If the molecules are excited to the $S_1$ state in organic solvents, QCT exhibits no fluorescence due to excited state intramolecular proton transfer (ESIPT) between the -OH and the carbonyl oxygen, but API shows significant fluorescence because ESIPT occurs slowly. If the molecules are excited to the $S_2$ state, both QCT and API exhibit strong $S_2{\rightarrow}S_o$ emission without any dual fluorescence. As the $H_2O$ composition of both solvents increases, the fluorescence intensity decreases rapidly due to the intermolecular hydrogen bonding interaction. The theoretical calculation further supports these results. The change in fluorescence properties as a function of the solvatochromic parameters was also studied.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.4 no.2
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• pp.51-56
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• 2018

Azeotropic drying process is routinely applied to enhance nucleophilicity of $[^{18}F]$fluoride ion during the nucleophilic production of PET radiotracers; however, the drying process requires usually 15-25 min. Due to the high demand of employing fluorine-18 ($t_{1/2}=109.8min$) in PET radiopharmaceutical production, several research groups have focused on the method development, obviating tedious removal process of the residual target water ($[^{18}O]H_2O$) for $[^{18}F]$fluoride ion complex to be used in radiofluorination. Some development in radiofluorination in a mixed organic solvent system was demonstrated with various aliphatic substrates, but only kryptand as a phase transfer agent was utilized in the reported method. Here, we extend to investigate the development scope of applicability with basic alkyl ammonium salt as a phase transfer agent through the extensive elution efficiency study and radiofluorination outcome for aliphatic radiofluorination.

• YAKHAK HOEJI
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• v.31 no.2
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• pp.45-51
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• 1987

Methyl orange(MO) and cetyltrimethylammonium bromide(CTA) were mixed and added to 10ml of the buffer solution and then the solution was shaken for 5 minutes. The maximum absorption wavelength of the reaction product was 419nm. Dichloromethane was the best extracting solvent among the several organic solvents and the most suitable pH range was 2~8. When the CTA-MO calibration curve was made in the best experimental condition, the Lambert-Beer's law was obeyed in the range of CTA concentration of $1.5\times$$10^{-5}$~1.0$\times$$10^{-4}M$ by UV spectrophotometer. This method was possible to determine quaternary ammonium salts in the pharmaceutical preparations.

• YAKHAK HOEJI
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• v.35 no.1
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• pp.15-21
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• 1991

Quaternary amines which are widely used as medicines are nitrogen compounds. Metanil yellow(MY) and benzalkonium chloride(BKC) were mixed and added to 10ml of the buffer solution and then the solution was shaken for 5 minutes. The maximum absorption wavelength of the reaction product was 402 nm. Dichloromethane was the best extracting solvent among the several organic solvents and the most suitable pH range was 2~8. When the BKC-MY calibration curve was made in the best experimental condition, the Lambert-Beer's law was obeyed in the range of BKC concentration of 2$\times$$10^{-6}$~9$\times$$10^{-6}$M by UV spectrophotometer. This method was possible to determine quaternary ammonium salts in the pharmaceutical preparation.

• Journal of Powder Materials
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• v.17 no.1
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• pp.44-51
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• 2010

The rheological behavior of a cordierite honeycomb extrusion paste was investigated by measuring torque values in a Brabender plastograph. The extrusion pastes were formulated using binder (methy cellulose, MC), solvent (water), plasticizer (ploy ethylene glycol, PEG) and lubricants (oleic acid, OA). The mixing sequence and optimum organic binder, at least for homogeneous mixed state, can be determined from the rheological point of view. 3%MC-30%$H_2O$-1.5%PEG-1.0%OA with respect to the cordierite powder was chosen as a binder composition for the extrusion process of cordierite powder.

• Bulletin of the Korean Chemical Society
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• v.1 no.3
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• pp.101-104
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• 1980

A sequential copolypeptide with repeating unit sequences, in which a glycyl residue is flanked progressively by two ${\gamma}$-benzyl-L-glutamyl residues, has been synthesized by poymerizing p-nitrophenyl ester of ${\gamma}$-benzyl-L-glutamyl-${\gamma}$ -benzyl-L-gutamyl-glycine. Polymers obtained were characterized by viscosity and infra-red spectral data. The highest molecular weight obtained was 21,000. Molecular conformation in solid state was found to be a mixed form of and |${\beta}$-structure. Polymers obtained were insoluble in the most of the organic solvents except in a strong acid like dichloroacetic acid, but in binary mixtures of solvents such as dichloroacetic acid-ethylene dichloride or dichloroacetic acid-chloroform, they were soluble within certain ranges of solvent compositions.