• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.215-224
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• 1989

Electrochemical reductions of $trans-[Co(en)_2X_2](ClO_4)_n$ (where X is cyanide, nitrite, ammonia, and isothiocyanate) were investigated by cyclic voltammetry and polarography at mercury and glassy carbon electrode. $trans-[Co(en)_2(CN)_2]ClO_4$ was reduced to Co(II) complex followed by adsorption to the mercury electrode. Cyanide ion was not released from the reduced Co(II) complex but the cyanide and (en) were released after the reduction to metallic cobalt. The other complexes except $trans-[Co(en)_2(CN)_2]ClO_4$ were reduced to cobalt(II) complexes followed by release of monodendate ligand, and (en) was released at the reduction step to metallic cobalt. $trans-[Co(en)_2(NO_2)_2]ClO_4$ was reduced to cobalt(Ⅱ) complex, and $NO_2^-$ ion was released followed by electroreduction through ECE mechanism at pH 2. On glassy carbon electrode, all complexes of Co(III) were reduced to Co(II) complexes with irreversible one-electron diffusion controlled reaction in which (en) was not released at this step. Increasing absorption wave number of complexes caused to negative shift of peak potential.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3707-3710
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• 2010

A chromo/fluorogenic $NO_2S_2$-macrocycle L functionalized with nitrobenzofurazan unit as a dual-signaling probe was synthesized and structurally characterized by single crystal X-ray analysis. In a cation-induced color change experiment, L exhibited excellent $Hg^{2+}$ ion selectivity by showing the color change from orange-red to yellow. However, this hypochromic shift by $Hg^{2+}$ was observed for the weaker coordinating anion system such as ${NO_3}^-$ and ${ClO_4}^-$ ions. The observed anion effect is due to the strong coordination of anions inhibits the bond formation between $Hg^{2+}$ and the macrocyclic tert-N atom, which is sensitive to induce the color change. In the fluorometric experiment, L showed chelate-enhanced fluorescence change effect only with $Hg^{2+}$ ion, together with a change from yellow to green emission. The sensing ability for $Hg^{2+}$ with the proposed chemosensor L is due to the stable complexation with 1:1 stoichiometry (metal-to-ligand).

• Journal of the Korean Chemical Society
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• v.31 no.6
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• pp.503-508
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• 1987

The protonation constants of 3,4 : 9,10-dibenzo-1,12-diaza-5,8-dioxacyclotetradecane $(NenOenH_4)$ and stability constants of its transition metal complexes have been determined by the potentiometric titration in 1 : 1 dioxane-water mixture with 0.1 ionic strength at $25^{\circ}C.$ For a given anion system, the stabilitv constants of the complexes are in the order of $Mn^{2+}<\;Co^{2+}\;< Ni^{2+}\;<\;Cu^{2+}\;>\;Zn^{2+}$, which accords with the Williams-Irving series.

• Bulletin of the Korean Chemical Society
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• v.13 no.5
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• pp.498-503
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• 1992

The protonation of RuH(NO)(Cyttp) resulted in the formation of $[RuH_2(NO)(Cyttp)]^+$ which is characterized as a classical cis-dihydried complex. This complex is fluxional and the intramolecular process involving a molecular hydrogen complex is proposed. This mechanism was further supported by the reactivity of this complex toward neutral 2-electron ligands. On the other hand, it failed to detect the existence of $[RuH_2(NO)(etp)]^+$ probably due to instability of the complex but the crystal structure of $[Ru(PMe_3)(NO)(etp)]^+$ formed by the protonation of RuH(NO)(etp) followed by the addition of $PMe_3$ was determined to have a trigonal bipyramidal structure with a linear NO in the equatorial plane and a facial etp ligand. The crystals are monoclinic, space group P21/n, with unit cell dimensions a = 14.130(2), b = 21.026 (3), c = 14.760 (1) ${\AA}$, ${\beta}$ = 97.88 $(l)^{\circ}$ V = 4344 ${\AA}^3$, Z = 4, R = 0.046 and $R_w$ = 0.056 for the 4779 intensities with $F_o^2 > 3{\sigma}(F_0^2)$ and the 440 variables.

• Journal of the Korean Chemical Society
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• v.38 no.2
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• pp.101-107
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• 1994

Some molybdenum(III) and (IV) complexes have been prepared from the reaction of $MoCl_4$·2MeCN with N, P, O-donating ligands and characterized by elemental analysis, infrared and UV-Visible spectroscopy. 3,5-Lutidine, 1,2-phenylenediamine, 8-hydroxyquinoline, 9,10-phenanthrenequinone, triphenylphosphine and 1,2-bis(diphenylphosphino)ethane were chosen as coordinating ligands. Stretching frequencies $\upsilon$ (Mo-Cl) of Mo(IV) appear at higher frequencies than those of Mo(III) complexes due to the increasing oxidation number of metal. $MoCl_4(L)_2$ exhibit one Mo-Cl stretching frequency, whereas Mo$Cl_4$(L^L) exhibit four Mo-Cl stretching frequencies. The number of Mo-Cl stretching frequency suggestes the former complexes have trans($D_{4h}$) and the latter complexes have cis($C_{2v}$) symmetry. Stretching frequency ${\nu}g(C{\equiv}N)$ of acetonitrile in Mo(III) complexes are shifted to about 30 $cm^{-1}$ higher frequency compared with that of a free ligand (2260 $cm^{-1}$). These spectral data indicates that Mo(III) complexes are in the octahedral geometries with the coordinated acetonitrile. Finally each molybdenum(III) and (IV) complexes showed the following formulation; $[MoCl_4(L)_2]$,[Mo$Cl_4$(L^L)], $[MoCl_3(L)_2MeCN]$ and [Mo$Cl_3$(L^L)MeCN].

• Journal of Life Science
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• v.20 no.6
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• pp.853-860
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• 2010

The DevSR two-component system is a major regulatory system involved in redox sensing in Mycobacterium smegmatis. The DevSR system consists of the DevS histidine kinase and its cognate DevR response regulator. When exposed to hypoxic conditions, the DevS histidine kinase is activated to phosphorylate the DevR response regulator, leading to the transcriptional activation of the DevR regulation. The ligand-binding state of the heme embedded in the N-terminal GAF domain of DevS determines the kinase activity of DevS. In this study, we demonstrated that the redox-responsive cysteine (C547) in the C-terminal kinase domain is involved in the redox-dependent control of DevS kinase activity. The formation of an intersubunit disulfide bond between the C547 residues in the presence of $O_2$ led to inactivation of DevS kinase activity. The reduction of the oxidized DevS with reductants such as $\beta$-mercaptoethanol and dithiothreitol resulted in the restoration of DevS kinase activity. It was demonstrated in vivo by complementation test that the substitution of C547 to alanine partially impaired the sensory function of DevS in M. smegmatis.

• Nuclear Medicine and Molecular Imaging
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• v.41 no.4
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• pp.326-334
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• 2007

Purpose: The estrogen receptor (ER), which is over-expressed in ER-positive breast tumors, has been imaged by positron emission tomography (PET) using $[^{18}F]$ labeled estrogen ligands, especially $[^{18}F]FES$. However, $[^{18}F]$ has relatively short-lived half-life ($t_{1/2}$ =1.8 h) and the labeling yield of radio-fluorination is usually low compared with $^{64}Cu\;(t_{1/2}=12.7\;h)$. 1,4,7,10-tetraazacyclododecane (cyclen) is used to form stable metal complexes with copper, indium, gallium, and gadolinium. With these in mind, we prepared cyclen-based Cu complexes which mimic estradiol in aspect of two hydroxyl groups. Materials and Methods: 1.7-Protected cyclen, 1.7-bis (benzyloxycarbonyl)-cyclen was synthesized according to the reported procedure. After introducing two 4-benzyloxybenzyl groups at 4,10-positions, the benzyloxycarbonyl and benzyl groups were removed at the same time by hydrogenation on Pd/C to give 1,7-bis(4-hydroxybenzyl)-1,4,7,10-tetraazacyclododecane (1). Results: The prepared ligand 1 was fully characterized by $^1H,\;^{13}C$ NMR, and mass spectrometer. The synthesized ligand was reacted with copper chloride and copper perchlorate to give copper complexes $[Cu(1)]^{2+}2(CIO_4^-)\;and\;[Cu(1)Cl]^+Cl^-$ which were confirmed by high-resolution mass (FAB). Conclusion: We successfully synthesized a cyclen derivative of which two phenol groups are located on trans position of N-atoms. And, two Cu(ll) complexes of +2 and +1 overall charge, were prepared as a potential PET tracers for ER imaging.

• BMB Reports
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• v.29 no.3
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• pp.230-235
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• 1996

The interaction of ${\alpha}-ketoglutarate$ dehydrogenase complex (${\alpha}-KGDC$) with a hydrophobic fluorescent probe [1,1'-bi(4-aniline)naphthalene-5,5'-disulfonic acid] (bis-ANS) was studied. The punfied ${\alpha}-KGDC$ was potently inhibited by bis-ANS with an apparent half maximal inhibitory concentration ($IC_{50}$) of 9.8 ${\mu}m$ at pH 8.0. The catalytic activities of both the E1o and E2o subunits were predominantly inhibited while that of the E3 component was hardly affected. The binding of bis-ANS to the enzyme caused a marked enhancement and blue shift from 523 nm to 482 nm in the fluorescence emission spectrum. The dissociation constant ($K_d$) and the number of binding sites (n) were calculated to be 0.87 mM and 158, respectively. Allosteric regulators such as purine nucleotides and divalent cations further increased the fluorescence intensity of the $bis-ANS-{\alpha}-KGDC$ binary complex. These data suggest that the binding of these allosteric regulators to ${\alpha}-KGDC$ may cause the conformational changes in the enzyme and that bis-ANS could be used as a valuable probe to study the interaction of the multi-enzyme complex and its allosteric regulators.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3617-3622
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• 2010

The reaction of stoichiometric amount of $FeCl_2{\cdot}4H_2O$, (2-pyridylmethyl, 3-pyridylmethyl)amine (2,3-pyma) and sodium azide/sodium thiocyanate in methanol under aerobic conditions affords the dinuclear Fe(III) complexes, [(2,3-pyma) $(N_3)_2Fe({\mu}-OCH_3)_2Fe(N_3)_2$(2,3-pyma)]${\cdot}CH_3OH$ (1) and [(2,3-pyma)$(NCS)_2Fe({\mu}-OCH_3)_2Fe(NCS)_2$(2,3-pyma)] (2) in good yield. Two bis-methoxy-bridged diiron(III) complexes are isolated and characterized. The coordination geometries around iron(III) ions in 1 and 2 are the same tetragonally distorted octahedron. The iron(III) ions are coordinated by two nitrogens of a 2,3-pyma, two nitrogens of two azide/thiocyanate ions, and two oxygens of two methoxy groups. Both compounds are isomorphous. The structures of 1 and 2 display the C-$H{\cdots}\pi$ and/or $\pi-\pi$ stacking interactions as well as hydrogen bonding interactions, respectively. Compounds 1 and 2 show significant antiferromagnetic couplings through the bridged methoxy groups between the iron(III) ions in the temperature range from 5 to 300 K ($H=-2JS_1{\cdot}S_2$, J=-19.1 and $-13.9\;cm^{-1}$ for 1 and 2).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.199-204
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• 2022

A new three-dimensional Gd-MOF, [Gd(p-XBP4)₄(H₂O)]·W(CN)₈; (1; p-XBP4 = N,N'-p-phenylenedimethylenbis (pyridin-4-one)) has been synthesized by slow-evaporation and its crystal structure was characterized by single-crystal X-ray diffraction (SCXRD) analysis. For each Gd^III ion, there are seven coordination sites, which are occupied by six oxygen atoms of six p-XBP4 ligands and one oxygen atom from the water molecule. The [W(CN)₈]^3- anion exists for charge balance with cationic framework. The Gd^II ions are interconnected by the p-XBP4 ligand to form the three-dimensional structure. Considering the magnetic property of lanthanide ions, magnetic studies of Gd-MOF were investigated by direct-current (DC) magnetic susceptibilities measurements.