• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.815-820
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• 2014

We applied the two-color resonant two-photon ionization and mass-analyzed threshold ionization techniques to record the vibronic and cation spectra of 2,4-difluorophenol. As supported by our theoretical calculations, only the cis form of 2,4-difluorophenol involves in the two-photon photoexcitation and pulsed field ionization processes. The band origin of the $S_1{\leftarrow}S_0$ electronic transition of cis-2,4-difluorophenol appears at 35 647 ${\pm}2cm^{-1}$ and the adiabatic ionization energy is determined to be 70 $030{\pm}5cm^{-1}$, respectively. Most of the observed active vibrations in the electronically excited $S_1$ and cationic ground $D_0$ states mainly involve in-plane ring deformation vibrations. Comparing these data of cis-2,4-difluorophenol with those of phenol, cis-2-fluorophenol, and 4-fluorophenol, we found that there is an additivity rule associated with the energy shift resulting from the additional fluorine substitution.

• 한국세라믹학회지
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• 제32권6호
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• pp.703-709
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• 1995

Octadecylenetrimethylammonium-montmorillonite as an organophilic montmorillonite intercalations complex was formed by cation exchange reaction between Na-montmorillonite and 9-octadecylenetrimethylammonium cation. After drying of this organophilic montmorillonite at $65^{\circ}C$ in high vacuum, the complexes were reacted with various swelling-solutions such as benzene, toluene, o-xylene, pyridine, $\alpha$-picoline, 2-ethyl-pyridine, 2-vinyl-pyridine and styrene, and the corresponding basal spacing obtained were 43.9$\AA$, 54.3$\AA$, 51.7$\AA$, 41.5$\AA$, 42.5$\AA$, 39.9$\AA$, 39.8$\AA$, 44.8$\AA$, respectively.

• Bulletin of the Korean Chemical Society
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• 제27권8호
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• pp.1099-1114
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• 2006

Our studies in the area of single electron transfer (SET) photochemistry have led to the discovery of efficient processes, in which regioselective formation of carbon-centered radicals takes place by nucleophile assisted desilylation of $\alpha$-trialkylsilyl substituted ether, thioether, amine and amide centered cation radicals. The rates of bimolecular desilylation of the intermediate cation radicals exceed those of other cation radical $\alpha$-fragmentation processes (e.g.,-deprotonation). This sereves as the basis for the design of highly regioselective, SET-induced photomacrocyclization reactions of polyether, polythioether, polyamide, and polypeptide linked phthalimides. Photocyclization reactions of trimethylsilyl-terminated substrates in these families are unique in that they produce polyfunctionalized macrocyclic substances in a highly efficient and regioselective manner. In addition, our studies in this area have led to important information about the factors that govern chemical and quantum efficiencies that should be applicable to a wide variety of redox processes promoted by SET from substrates containing more than one electron donor site.

• Journal of Photoscience
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• 제8권2호
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• pp.67-69
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• 2001

Radical cations of DPBEY and PPCB were generated by ${\gamma}$-radiolysis and pulse radiolysis in halogenated solvents. The radical cation PPCB+ shows 505 (shoulder) and 520 nm absorption peaks with 700 ns lifetime in agreement with the laser flash photolysis work and strongly support the exciplex mechanism proposed for the photoreaction of PPCB and dimethylfumarate.

• 한국자기공명학회논문지
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• 제4권2호
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• pp.82-90
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• 2000

Photoinduced charge separation of alkylphenothiazines in molecular assemblies such as positively, negatively and neutrally charged micelle interface results in the paramagnetic phenothiazine cation radical. This was studied as a model system for the light energy conversion into chemical energy. The photoproduced phenothaizne cation radical was identified and its amount was quantized with electron spin resonance (ESR). The microenvironment of photoproduced cation radical was studied with pulsed-ESR. Such a charge separation is enhanced by the optimization of various structural factors of the molecular assemblies. The structural factors of molecular assemblies have focused on the interface charge, interface structure with different headgroups and interfacial perturbation by disolving interface active organic additives.

• Journal of Information Display
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• 제13권3호
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• pp.97-100
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• 2012

We have conducted two kinds of the so-called charge-compensated aliovalent element substitutions to control the photoluminescence properties of $NaAlSiO_4:Eu^{2+}$ with a special focus on the enhancement of the excitation intensity at 400 nm. The aliovalent element substitutions include cation-cation and cation-anion co-substitutions according to the general formulas $Na_{1-x}M_xAl_{1+x}Si_{1-x}O_4:Eu^{2+}$ and $Na_{1-x}M_xAlSiO_{4-x}N_x:Eu^{2+}$ (M = $Mg^{2+}$, $Ca^{2+}$, and $Sr^{2+}$), respectively. The increase in the relative excitation intensity at 400 nm has been achieved in both types of the co-substitutions. Thus, the present research has demonstrated the effectiveness of the charge-compensated element substitution.

• 분석과학
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• 제11권6호
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• pp.495-498
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• 1998

The effect of high concentration ion matrix on the analysis of low anion concentration in the suppressed ion chromatography was studied. The anions studied were $Br^-$, $NO_3{^-}$, $HPO_4^{2-}$, $SO_4^{2-}$, and $C_2O_4^{2-}$ in the presence of excess NaCl and $CaCl_2$. In this study we suggested that the erroneous results in the suppressed ion chromatographic determination of small concentration of anions were not caused by the interaction of large amount of cation in the suppressor, but by the interaction of cation with concerned anion in the original solution. The error in the analysis of such anion can not be eliminated just by dilution. Therefore, we suggested that standard addition method might be adequate for analyses of those samples.

• Journal of Magnetics
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• 제19권2호
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• pp.101-105
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• 2014

In this work, Zinc ferrite nanoparticles have been prepared by various methods, conventional (ZC), mechanochemical processing (ZM) and Sol-Gel (ZS) method, to compare their structural and magnetic properties. The cation distribution obtained from XRD shows the degrees of inversions are 4%, 14.8%, and 16.4% from the normal $ZnFe_2O_4$ structure. Fourier transform infrared spectroscopy (FT-IR) confirms changes in cation distribution of $ZnFe_2O_4$ fabricated by sol-gel and mechanochemical processing. The $^{57}Fe$ M$\ddot{o}$ssbauer spectra of the samples were recorded at room temperature. The spectra exhibit a line broadening. The magnetic properties of the samples were studied by vibration sample magnetometer (VSM) at room temperature and the results show that the sample ZM has ferrimagnetic behaviour.

• 대한화학회지
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• 제39권1호
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• pp.71-75
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• 1995

Tricarbonyl(2-methyl-1-phenylpentadienyl)iron(+1) hexafluorophosphate 양이온이 hexafluorophosphoric acid를 사용한 tricarbonyl(4-methyl-5-hexadien-1-ol)iron의 양성자 첨가반응에 의해 얻어졌다. 그 양이온과 $H_2o$, dimethyl cuprate, diphenylacetylenyl cuprate, 그리고 cyclohexanone의 enolate와의 반응은 그것들에 대응하는 (η4-1,3-diene)Fe(CO)3를 형성시켰다. 친핵체의 공격에 있어서의 위치 선택성은 주로 입체효과의 결과인 것으로 보인다.

• Bulletin of the Korean Chemical Society
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• 제29권2호
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• pp.339-341
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• 2008

Catalytic trimerization of isobutene to produce triisobutenes has been performed over cation-exchange resin and zeolite catalysts. Resin catalysts have the advantage of long lifetime and high trimers selectivity even though the regeneration of an aged catalyst is not satisfactory. On the contrary, zeolite catalysts can be regenerated facilely by simple calcination in air even though the lifetime is short and trimers selectivity is low probably due to small pore size and strong acidity, respectively. It is, therefore highly desirable to develop an inorganic acid catalyst with macro- or meso-pores to show catalytic performances similar or superior to those of macroporous resin catalysts.