• Journal of the Korean Chemical Society
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• v.57 no.3
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• pp.352-356
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• 2013

In this work, a new cadmium complex $[Cd(L)(CH_3COO)_2].2H_2O$ (1) with the ligand L, N,N'-bis(2-pyridinecarboxalidene)-1,2-cyclohexanediamine was prepared and identified by elemental analysis, FT-IR, Raman, $^1H$ NMR spectroscopy and single-crystal X-ray diffraction. The cadmium atom in the crystal structure of 1 has distorted triangular dodecahedral geometry by coordination of the four nitrogen atoms of L and four oxygen atoms of the two acetate ions. Two water molecules are also incorporated in the crystal network. The $O-H{\cdots}O$ hydrogen bonds present in the crystal structure of 1. In this work, three structural surveys including coordination numbers of the cadmium atom, coordination modes of L and resonance in pyridine-2-ylmethanimine-based compounds are presented.

• Bulletin of the Korean Mathematical Society
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• v.47 no.5
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• pp.961-971
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• 2010

As an application of 'reverse engineering' technique introduced by R. Fintushel, D. Park and R. Stern [9], we present a simple way to construct an infinite family of exotic (2n+2l-1)$\mathbb{CP}^2#$(2n+4l-1)$\overline{\mathbb{CP}}^2$'s for all $n\;{\geq}\;0$, $l\;{\geq}\;1$.

• Bulletin of the Korean Chemical Society
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• v.8 no.3
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• pp.200-202
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• 1987

Various useful relations involving Hammett's and $Br{\phi}nsted's$ coefficients are derived for cross interactions between identical groups: ${\rho}_{ii}={\rho}^N+{\rho}^L$, ${\rho}^L-{\rho}^N=1$, ${\beta}_{ii}={\beta}_N+{\beta}_L$ and ${\beta}_N-{\beta}_L=1$. The use of these relations enable us to correctly interprete the transition state structure. Another advantage of the use of these relations is to use ${\rho}/{\rho}_e$ for the determination of corresponding ${\beta}$ values instead of plotting log k vs $pK_{lg}$, once ${\rho}_e$ values for standardizing equilibria are obtained.

• Journal of the Korean Chemical Society
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• v.43 no.2
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• pp.28-231
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• 1999

• Bulletin of the Korean Mathematical Society
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• v.47 no.1
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• pp.1-15
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• 2010

Let M be a real hypersurface with almost contact metric structure $(\phi,g,\xi,\eta)$ in a complex space form $M_n(c)$, $c\neq0$. In this paper we prove that if $R_{\xi}L_{\xi}g=0$ holds on M, then M is a Hopf hypersurface in $M_n(c)$, where $R_{\xi}$ and $L_{\xi}$ denote the structure Jacobi operator and the operator of the Lie derivative with respect to the structure vector field $\xi$ respectively. We characterize such Hopf hypersurfaces of $M_n(c)$.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.894-898
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• 2011

The first example of lead compound from $Pb(NO_3)_2$ and $H_3L$ N-heterocyclic ligand $(H_3L\;=\;(HO_2C)_2(C_3N_2)(C_3H_7)CH_2(C_6H_4)(C_6H_3)CO_2H)$, $[Pb_4(L')_4]{\cdot}5H_2O$ 1 (L' = OOC$(C_3H_7)(C_3N_2)CH_2(C_6H_4)(C_6H_3)COO)$, has been obtained under hydrothermal condition by decarboxylation, and characterized by elemental analysis, IR, TGDTA, and single-crystal X-ray diffraction. Compound 1 possesses a rare two-dimensional upper-lower offset terrace-like layer structure. In 1, crystallographic distinct Pb(II) ion adopts five-coordination geometry, and two lattice water molecules occupy the voids between 2-D layers. Results of solid state fluorescence measurement indicate that the emission band 458 nm may be assigned to $\pi^*-n$ and $\pi^*-\pi$ electronic transitions within the aromatic systems of the ligand L', however, the emission bands centred at 555 nm, 600 nm and 719 nm may be derived from phosphorescent emission ($\lambda_{excitation}$ = 390 nm).

• Polymer(Korea)
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• v.24 no.4
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• pp.445-452
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• 2000

The copolymerization of ethylene (E) and norbornene (N) was examined by using various metallocene catalysts and modified-MAO(MMAO) cocatalyst. For $C_2$-symmetry catalysts such as rac-Et(Ind)$_2$ZrC $l_2$, M $e_2$Si(Ind)$_2$ZrC $l_2$, M $e_2$Si(Cp)$_2$ZrC $l_2$ and Cs-symmetrical iPr(FluCp)ZrC $l_2$ as well as CGC and di-bridged zirconocene, the effects of catalyst structure and [N]/[E] feed ratio on catalyst activity, thermal property and [N] content of copolymer (COC) was investigated. For rac-Et(Ind)$_2$ZrC $l_2$ catalyst of a constant [N]/[E] feed ratio, the appropriate conditions of [Al]/[Zr] mole ratio, polymerization temperature and cocatalyst structure were found to be 3000, 4$0^{\circ}C$, MMAO cocatalyst, respectively. As [N]/[E] feed ratio increased, the incorporation of norbornene to copolymer increased while, the activity of catalyst decreased except for iPr(FluCp)ZrC $l_2$ With consideration of catalyst activity as well as N content, it was found that rac-Et(Ind)$_2$ZrC $l_2$/MMAO system exhibited relatively high activity and controllable $T_{g}$. Monomer reactivity ratio was determined by Kelen-Tudos method..

• Korean Journal of Materials Research
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• v.20 no.4
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• pp.187-193
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• 2010

Chromium nitride (CrN) samples with two different layer structures (multilayer and single layer) were coated on bipolar plates of polymer electrolyte membrane fuel cells (PEMFC) using the reactive sputtering method. The effects with respect to layer structure on corrosion resistance and overall cell performance were investigated. A continuous and thin chromium nitride layer ($Cr_{0.48}\;N_{0.52}$) was formed on the surface of the SUS 316L when the nitrogen flow rate was 10 sccm. The electrochemical stability of the coated layers was examined using the potentiodynamic and potentiostatic methods in the simulated corrosive circumstances of the PEMFC under $80^{\circ}C$. Interfacial contact resistance (ICR) between the CrN coated sample and the gas diffusion layer was measured by using Wang's method. A single cell performance test was also conducted. The test results showed that CrN coated SUS316L with multilayer structure had excellent corrosion resistance compared to single layer structures and single cell performance results with $25\;cm^2$ in effective area also showed the same tendency. The difference of the electrochemical properties between the single and multilayer samples was attributed to the Cr interlayer layer, which improved the corrosion resistance. Because the coating layer was damaged by pinholes, the Cr layer prevented the penetration of corrosive media into the substrate. Therefore, the CrN with a multilayer structure is an effective coating method to increase the corrosion resistance and to decrease the ICR for metallic bipolar plates in PEMFC.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1905-1910
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• 2008

The reaction of 3,14-dimethyl-2,6,13,17-tetraazatetracyclo[16.4.0$0^{1.18}.0^{7.12}$]docosane ($L^1$) with formaldehyde in warm methanol yielded 3,14-dimethyl-2,6,13,17-tetraazatetracyclo[16.4.$1^{2.6}.0^{1.18}.0^{7.12}$]tricosane ($L^7$) containing one 1,3-diazacyclohexane subunit. In methanol, $L^7$ readily reacts with $Cu^{2+}$ ion to form [$CuL^7(H_2O)$]$^{2+}$ which is extremely inert against methanolysis. In the solution containing $Ni^{2+}$ ion, however, $L^7$ reacts with methanol to yield [$NiL^3$]$^{2+}$ ($L^3$ = 2-(methoxymethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.$0^{1.18}.0^{7.12}$]- docosane), in which one N-$CH_2OCH_3$ pendant arm is appended. The copper(II) complex [$CuL^7(H_2O)$]- $(ClO_4)_2{\cdot}3H_2O\;(I{\cdot}3H_2O)$ has a severely distorted trigonal bipyramidal coordination geometry with a 4-5- 6-5 chelate ring sequence. The crystal structure of [$NiL^3$]$(PF_6)_2{\cdot}2H_2O$ (IIb) shows that the N-$CH_2OCH_3$ pendant arm is not coordinated to the metal ion in the solid state. In various solvents (S), however, the nickel(II) complex exists as a mixture of [$NiL^3$(S)]$^{2+}$, in which the N-$CH_2OCH_3$ group as well as S is coordinated to the metal ion, and [$NiL^3$]^{2+}.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1175-1179
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• 1998

The aerobic reaction of 2-(acetylpyridine)-S-methyldithiocarbazate (acpy-mdtcH) and 2-(acetylpyridine)-N-phenylthiosemicarbazate(acpy-phTscH) with manganese(Ⅱ) acetate affords Mn(acpy-mdtc)2 and Mn(acpyphTsc)2, respectively. The spectroscopic data and X-ray structure of Mn(acpy-mdtc)2 are reported. Crystal data for Mn(acpy-mdtc)2; C18H20N6S4Mn, mol wt 503.58, monoclinic crystal system(P21/c) a=12.240(5) Å, b= 10.918(l) Å, c=17.651(3) Å, β=105.93(2), and V=2268(l) Å3, Z=4, 5071 data collected with 0°< 2θ < 52.64°, 2995 data with I > 3σ(I), R= 0.046, Rw= 0.065. The ligands act as tridentate NNS donors. The two Mn-S distances are not equal, and respectively 2.512(2) Å and 2.541(2) Å. The average Mn-N (azomethine) length, 2.242(5) Å, is slightly shorter than the average Mn-N (pyridyl) length, 2.262(5) Å. The coordination environment about MN(Ⅱ) center deviates considerably from octahedral geometry. The manganese(Ⅱ)-manganese(Ⅰ) and manganese(Ⅰ)-manganese(0) reduction potentials of Mn(acpy-mdtc)2 are ∼-l.71 and ∼-l.98 V while those of Mn(acpy-phTsc)2 are ∼-l.87 and ∼-2.11 V vs. Ag/Ag+ in dimethyl sulfoxide, respectively.