• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.218-224
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• 2014

In order to explore new coordination frameworks with novel designed 3-nitrophthalic acid and the same N-donor ancillary ligand, a series of novel coordination complexes, namely, $[Cd_2(3-NPA)_2(TBZ)_2(H_2O)_2]{\cdot}2H_2O$(1), $[Zn_2(3-NPA)_2(TBZ)_2]$(2), $[Zn_2O(3-NPA)(TBZ)(H_2O)]_n$(3), $[Co(3-NPA)(TBZ)(H_2O)]_n$(4) (3-$NPAH_2$ = 3-nitrophthalic acid), have been hydrothermally synthesized through the reaction of 3-nitrophthalic acid with divalent transition-metal salts in the presence of N-donor ancillary coligand (TBZ = thiabendazole). As a result of various coordination modes of the versatile 3-$NPAH_2$ and the coligand TBZ, these complexes exhibit structural diversity. X-ray structure analysis reveals that 1 and 2 are 0D molecular rings, while 3 and 4 are one-dimensional (1D) infinite chain polymers. And the weak O-H${\cdots}$O hydrogen bonds and C-H${\cdots}$O nonclassical hydrogen bonds as well as ${\pi}-{\pi}$ stacking also play important roles in affecting the final structure where complexes 1, 3 and 4 have 3D supramolecular architectures, while complex 2 has a 2D supramolecular network. Also, IR spectra, fluorescence properties and thermal decomposition process of complexes 1-4 were investigated.

• Korean Journal of Crystallography
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• v.2 no.1
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• pp.12-16
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• 1991

C18H22N4OS, Mr=342.47, monoclinic, P2₁/c,a=11.802(2), b=31.962(2), c=9.829(2)A, β=100.12(1)˚, V=3694.8A3,F(000)=1472, Z=8, Dx=1.246 Mg m-3, Dm=1.17Mg m-3,λ=0.71073 A, μ=0.15mm-1, T=294 K. final R=0.0856 for 3718 observed reflection (Fo>3σ(Fo)) There are two molecules in an asymmetric unit and a major difference between these molecules is in the C(9)-N(1)-C(6)-C(7) torsion angles [58.8(8)˚and 1(1)˚]. Both molecules have intramolecular N(1)-H(10)'N(3) hydrogen bonds [ 2.613(7) and 2.566(7) A] and assume V-shaped conformation with N(2) atoms at the verices. The two independent molecules are linked by the two N(2)-H(11)'S' hydrogen bonds[3.367(5) A and 3.421(4)A] and the dimergen are held together by van der Waals forces.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.597-601
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• 2006

The degradation of the Nafion membrane by oxygen radical (OH, $HO_2$) was investigated in Polymer electrolyte membrane fuel cell (PEMFC). Nafion membrane was degraded in Fenton solution consisted with hydrogen peroxide (10-30％) and ferrous ion (1-4 ppm) at $80^{\circ}C$. After degradation in Fenton solution, C-F, S-O and C-O chemical bonds of membrane were broken by oxygen radical attack. Breaking of C-F bond reduced the mechanical strength of Nafion membrane, and hence induced pinholes, resulting in increase of $H_2$ crossover through the membrane. Decomposition of S-O and C-O bonds decreased the ion exchange capacity of the electrolyte membrane. The performance of unit cell composed the membrane, which was degraded in 30％ $H_2O_2$ with 4ppm $Fe^{2+}$ solution for 48 hr, was about half times as low as one with normal membrane.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1013-1019
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• 2007

Amorphous silicon and silicon-nitride films were deposited using plasma-enhanced chemical vapor deposition (PECVD) method at $150^{\circ}C$. As fraction of $H_2$ in source gas was increased, characteristics of low-temperature silicon-nitride films approached those of conventional high-temperature films; the refractive index approached 1.9 and the ratio of nitrogen-hydrogen bonds to silicon-hydrogen bonds increased. And also, as fraction of $H_2$ in source gas was increased, characteristics of low-temperature silicon films approached those of conventional high-temperature films; refractive index and optical band gap approached 4.2 and 1.8 eV, and $[Si-H]/([Si-H]+[Si-H_2])$ increased. Lower RF power and process-pressure made the amorphous silicon films to be better properties. Increase of $H_2$ ratio seemed as the common factor to get reliable amorphous silicon and silicon-nitride films for thin-film-transistors (TFTs) at low temperature.

• Journal of the Korean Chemical Society
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• v.13 no.2
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• pp.131-136
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• 1969

The crystal structure of rubidium hydrogen carbonate has been determined by single crystal X-ray diffraction method. the crystals are monoclinic with a = 15.05 $\AA$, b = 5.83 $\AA$, c = 4.02 $\AA$, and $\beta$ = $107^{\circ}.$ There are four chemical units per unit cell and the space-group was fixed as $C2-C^3_2$. Patterson and trial-and-error methods gave the approximate structure and its refinements were made by two-dimentional Fourier summation. The Co3 group is planar with tshhe C-O distances of 1.32 $\AA$, 1.32 $\AA$, and 1.33 $\AA$ within experimental error and the two $CO_3$ groups are linked together to form a complex anion [$H_2C_2O_6$] with the O-H${\cdot}{\cdot}{\cdot}$O distance, 2.53 $\AA.$ Two molecules of $RbHCO_3$ make the dimer structure with two hydrogen bonds. The values of reliability factor for $F_{(hol)}$, $F_{(hko)}$and $F_{(okl)}$are 0.15, 0.15 and 0.17 respectively. Each rubidium ion has eight oxygen neighbours with the Rb-O distances of 2.84~3.11 $\AA.$.

• Archives of Pharmacal Research
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• v.14 no.2
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• pp.137-142
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• 1991

The structure of a $\beta$-allyl type phenylpropanoid was determined by single crystal X-ray diffraction analysis. The compound was recrystallized from a mixture of n-hexane and benzene in monoclinic crystal system with a = 24.782 (2), b = 10.537 (1), c = 7.871 (1) ${\AA}, \beta=95.74$ (1)$^\circ, $D_x$=1.216, $D_m$=1.22g/$cm^3$, space group $P2_1/a$, and Z=4. The structure was solved by direct method and refined by least-squares procedure to the final R value of 0.054 for 2824 observed reflections {$F{\geq}3\sigma(F)$}. The molecular geometry shows a most stable trans-form with respect to the bulky phenyls, and this conformation is settled by an intramolecular hydrogen bond. In the crystal, the molecules are arranged along with the screw axis, and stabilized by the $O{\cdot}H{\cdots}O$ type intermolecular hydrogen bonds. The other intermolecular contacts appear to be the normal van der Waals' interactions. The compound is a dimeric phenylpropanoid, and belongs to the neolignan analogues.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.409-415
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• 1993

A potential function is applied to a hydrogen bonded system such as O-H---O and is slightly modified to provide a good understanding of a range of data. The use of this model requires a knowledge of terms describing the Van der Waals repulsion and the electrostatic interaction and the determination of these terms form the equilibrium conditions is described. Using this simple model, it will be shown that the relationship between the frequency shift and enthalpy of hydrogen bond formation is predicted to be linear and this is in reasonable agreement with experimental results in the literature.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3279-3282
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• 2010

The reaction rates of 4-X-2,6-dinitrochlorobenzenes (X = $NO_2$, CN, $CF_3$) with Y-substituted benzylamines (Y = p-$OCH_3$, p-$CH_3$, H, p-Cl) in MeOH-MeCN mixtures were measured by conductometry at $25^{\circ}C$. It was observed that the rate constant increased in the order of X = $NO_2$ > CN > $CF_3$ and in the order of Y = p-$OCH_3$ > p-$CH_3$ > H > p-Cl. When the solvent composition was varied, the rate constant increased in the order of 100% MeOH < 50% (v/v) MeOH-MeCN < 100% MeCN. These results may be ascribed to the formation of hydrogen bonds between the alcoholic hydrogen and nitrogen of benzylamines in groud state (GS). We conclude that the reaction takes place via $S_NAr$ base on the transition state parameters ${\rho}x$, ${\rho}Y$, $\beta_{nuc}$, and solvent effects.

• Journal of Pharmaceutical Investigation
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• v.26 no.1
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• pp.55-59
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• 1996

The crystal structure of diflunisal, 2',4'-difluoro-4-hydroxy-3-biphenyl-carboxylic acid, was determined by single crystal X-ray diffraction technique. The compound was recrystallized from a mixture of acetone and water in monoclinic, space group C2/c, with $a\;=\;34.666(6),\;b\;=\;3.743(1),\;c\;=\;20.737(4)\;{\AA},\;{\beta}=\;110.57(2)^{\circ}$, and Z = 8. The calculated density is $1.324\;g/cm^3$. The structure was solved by the direct method and refined by full matrix least-squares procedure to the final R value of 0.045 for 1299 observed reflections. It was found that the molecules in the crystal are partially disordered, that is, the two equivalent conformers $(180^{\circ}$ rotated ones through C(1)-C(7)) are packed alternatively without regular symmetry or sequence. The two phenyl rings of the biphenyl group is tilted to each other by the dihedral angle of $43.3^{\circ}$. The carboxyl group at the salicylic moiety is just coplanar to the phenyl ring, and the planarity of this salicylic moiety is stabilized by an intramolecular hydrogen bond of O(3)-H(O3) O(2). The molecules are dimerized through the intermolecular hydrogen bonds at the carboxyl group in the crystal.

• Genomics & Informatics
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• v.8 no.2
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• pp.70-75
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• 2010

Asp66his, Asp54Lys, and Asp50Asn are mutations in connexin 26 that are observed in the clinic and give rise to autosomal dominant syndromes. They are the result of point mutations in the human gap junction ${\beta}-2$ gene. In order to investigate the structural mechanism of Bart-Pumphrey Syndrome, Keratitis-Ichthyosis-Deafness Syndrome, and Vohwinkel Syndrome, homology modeling was carried out. Asp66 has direct contact with Asn62 by two hydrogen bonds in the wild-type protein, and in Asp66His, the biggest change observed is a tremendous energy increase caused by hydrogen bond breakage to Asn62. Shifts in the side chain and new hydrogen bond formation are observed for Lys54 compared to the wild-type protein (Asn54) and result in closer contact to Val84. Asp50Asn causes a significant decrease in bond energy, and residual charge reversal repels the ion and metabolites and, hence, inhibits their transportation. Such perturbations are likely to be a factor contributing to abnormal functioning of ion channels, resulting cell death and disease.