• Bulletin of the Korean Chemical Society
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• 제34권3호
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• pp.725-730
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• 2013

An investigation of the coordination behavior of sulfur-containing mixed-donor tribenzo-macrocycles $L^1-L^3$ ($L^1$: 20-membered $O_3S_2$, $L^2$: 20-membered $O_2S_3$, and $L^3$: 23-membered $O_4S_2$) with $d^{10}$-metal ($Ag^+$, $Hg^{2+}$, and $Pb^{2+}$) salts is reported. The X-ray structures of five complexes (1-5) with different structural types and stoichiometries, including mono- to dinuclear species have been determined. Reactions of $L^2$ and $L^3$ with the silver(I) salts ($PF_6{^-}$ and $SCN^-$) afforded two dinuclear 2:2 (metal-to-ligand) complexes with different arrangements: a sandwich-type cyclic dinuclear complex $[Ag_2(L^2)_2](PF_6)_2{\cdot}3CH_2Cl_2$ (1) and a linear dinuclear complex $[Ag_2(L^3)_2(SCN)_2]$ (2), in which two monosilver(I) complex units are linked by an Ag-Ag contact. Reactions of $L^1$ and $L^2$ with mercury(II) salts ($SCN^-$ and $Cl^-$) gave a mononuclear 1:1 complexes $[Hg(L^1)(SCN)_2]$ (3) and $[Hg(L^2)Cl_2]$ (4) with anion coordination in both cases. $L^2$ reacts with lead(II) perchlorate to yield a mononuclear sandwich-type complex $[Pb(L^2)_2(ClO_4)_2]$ (5), giving an overall metal coordination geometry of eight with a square antiprism arrangement. From these results, the effects of the donor variation and the anioncoordination ability on the resulting topologies of the soft metal complexes are discussed.

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2771-2775
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• 2011

Poly-ethylenedioxypyrrole (PEDOP) coated thiolated multiwall carbon nanotubes palladium nanoparticles (MWCNTs-Pd) modified glassy carbon electrode (GCE) [PEDOP/MWCNTs-Pd/GCE] for the determination of hydroquinone (HQ) and it’s isomer catechol (CA) were synthesized and compared with bare GCE and thiolated multiwall carbon nanotubes (MWCNTs-SH/GCE). The modification could be made by simple processes on a GCE with MWCNTs-Pd covered by PEDOP in a 0.05 M tetrabutylammonium perchlorate (TBAP)/MeCN solution system. A well-defined peak potential evaluation of the oxidation of hydroquinone to quinone at 0.05 V (vs. Ag/AgCl), and electrochemical reduction back to hydroquinone were found by cyclic voltammetry (CV) in phosphate buffered saline (PBS) at pH 7.4. Peak current values increased linearly with increasing hydroquinone contents. The peak separation between the anodic and cathodic peaks at the PEDOP/MWCNTs-Pd/GCE was ${\Delta}Ep$ = 40 mV for HQ and ${\Delta}Ep$ = 70 mV for CA, resulting in a higher electron transfer rate. Moreover, good reproducibility, excellent storage stability, a wide linear range (0.1 ${\mu}M$ - 5 mM for HQ and 0.01 ${\mu}M$ - 6 mM for CA), and low detection limits ($2.9{\times}10^{-8}$ M for HQ and $2.6{\times}10^{-8}$ M for CA; S/N = 3) were determined using differential pulse voltammetry (DPV) and amperometric responses; this makes it a promising candidate as a sensor for determination of HQ and CA.

• 전기화학회지
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• 제12권1호
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• pp.54-60
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• 2009

The redox characteristics of 2-arylaldehydehydrazono-3-phenyl-5-substituted-2, 3-dihydro-1, 3, 4-thiadiazoles (1a-h) have been investigated in nonaqueous solvents such as 1, 2-dichloroethane (DCE), dichloromethane (DCM), acetonitrile (AN), Tetrahydrofuran (THF), and dimethylsulfoxide (DMSO) at platinum electrode. Through controlled potential electrolysis, the oxidation and reduction products of the investigated compounds had been separated and indentified. The redox mechanism had been suggested and proved. It had been found that all the investigated compounds were oxidized in two irreversible one-electron processes following the well-known pattern of The EC-mechanism; the first electron loss gives the corresponding cation-radical which is followed by proton removal from the ortho-position in the N-phenyl ring forming the radical. The obtained radical undergoes a second electron uptake from the nitrogen in the N = C group forming the unstable intermediate (di-radical cation) which undergoes ring closure forming the corresponding cation. The formed cation was stabilized in solution through its combination with a perchlorate anion from the medium. On the other hand, these compounds are reduced in a single two-electron process or in a successive two one-electron processes following the well known pattern of the EEC-mechanism according to the nature of the substituent; the first one gives the anion-radical followed by a second electron reduction to give the dianion which is basic enough to abstract protons from the media to saturate the (C = O) bond.

• 대한화학회지
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• 제48권2호
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• pp.137-143
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• 2004

5.0${\times}10^{-2}$ M LiClO4 지지전해질에서 2-mercapto-1-methyl-imidazole(MMI)의 분석을 펄스차이폴라로그래피로 조사하였다. MMI의 분석에서 적절한 조건은 다음과 같다; 초기전위: -0.9 volts, 펄스세기: 0.08 mV, 주사속도: 2 mV/sec. 표준검량곡선은 1.0${\times}10^{-7}{\sim}8.0{\times}10^{-5}$ M 범위에서 좋은 직선성을 보였으며, 검출한계는 (2.2${\pm}0.1){\times}0.1^{-9}$ M이었다. 이 방법으로 첨가제의 방해없이 항갑상선 약제중의 MMI를 정량하는데 응용하였다.

• BMB Reports
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• 제31권6호
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• pp.560-564
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• 1998

Echinomycin-7 is an echinomycin derivative, Smethylated sulfonium perchlorate of echinomycin. We studied the in vitro cytotoxicity and in vivo antitumor activity of echinomycin-7 against P388 leukemia cells and compared the results with echinomycin. With respect to the cytotoxic effects, echinomycin-7 had cell line-dependent $IC_{50}$ values while echinomycin had similar values to several tumor cell lines. Also, in vivo antitumor activities were observed in tumor-bearing mice treated with both agents, which showed that echinomycin-7 had a broad therapeutic dose range. We also observed the apoptosis on leukemia cells treated with echinomycin-7 which exihibited the ladder pattern of DNA on electrophoresis. In addition to apoptosis, echinomycin-7 arrested $G_1/S$ phases of the cell cycle at the same time. We then examined the signaling pathway of echinomycin-7-induced apoptosis and showed that ERK of the MAP kinase family was activated and translocated into the nucleus by echinomycin-7 stimulation. This study suggests that echinomycin-7 acts as an antitumor agent through in vitro cytotoxicity and has in vivo antitumor activity against leukemia cells, and that the echinomycin-7- induced apoptosis might involve signal transduction via MAP kinases.

• 분석과학
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• 제8권1호
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• pp.17-23
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• 1995

$5.0{\times}10^{-2}M$ $LiClO_4$ 용액 중에서 펄스차이 폴라그래피로 2-mercapto-1-methyl-imidazole(MMI)의 정량방법을 조사하였다. 분석의 최적 조건은 초기전위 -0.9 volt vs. Ag/AgCl, 펄스높이 80mV, 주사속도 2mV/sec, 중간 크기 수은방울이었다. 검정곡선은 $1.0{\times}10^{-7}M$에서 $8.0{\times}10^{-5}M$ 범위까지 좋은 직선성을 보여 주었으며, 검출한계는 $2.2{\times}10^{-9}M$이었다. 이 방법은 다른 첨가제의 방해 없이 항갑상선 치료제 중의 MMI 정량에 응용할 수 있었다.

• 공업화학
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• 제10권6호
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• pp.822-827
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• 1999

본 연구에서는 에너지 밀도가 큰 초고용량 캐패시터를 제작하기 위한 기초 연구로서 활성탄소섬유의 물성과 유기 전해질의 특성이 초고용량 캐패시터의 전기화학적 특성에 미치는 영향을 조사하였다. 유기성 전해질의 경우는 이온의 크기가 수용성 전해질 보다 훨씬 크기 때문에 탄소전극의 세공크기에 많은 영향을 받으며, 용량을 발현할 수 있는 유효세공의 크기가 커야 한다는 것을 알 수 있었다. 혼합용매를 이용한 전해액의 조성은 큰 비축전용량과 빠른 충전속도, 그리고 낮은 ESR 및 방전전류의 세기에 대한 높은 비축전용량 유지성 등의 우수한 충방전 특성을 나타내는 것을 알 수 있었고, 전해질의 높은 이온전도도가 용량발현 및 자가방전 특성에 큰기여를 하고 있으며, 전해질 이온의 크기는 충전속도에 많은 영향을 미치는 것을 알 수 있었다.

• 공업화학
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• 제10권6호
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• pp.902-906
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• 1999

메틸셀루로스를 호스트고분자로 하고 copper(II) percolate를 산화제로 사용하여 기상상태에서 직접중합방법으로 전도성 복합필름을 합성하였다. 필름으로서 우수한 성형성과 기계강도를 갖고 있는 메틸셀루로즈는 PVA와 키토산과는 달리 피롤에 대하여 높은 친화성을 나타내어서 기상중합시 호스트고분자로 적합하였다. 기상중합법으로 합성된 폴리피롤은 복합재료 내에서 전도성네트워크를 형성하여 전도성 복합필름의 전기전도도는 $10^{-1}-10^{-7}S/cm$를 나타내었다. 피롤이 호스트고분자 내에서의 폴리피롤로 중합이 되는 정도를 UV-vis분광계로 확인하였다. 전도성 복합필름의 전기전도도와 기계강도는 산화제의 농도와 합성시간에 크게 의존하였다. TGA분석결과는 호스트고분자 내에 형성된 폴리피롤은 복합재료의 열적 안정성에 영향을 미치지 않는다. 전자현미경 분석결과 폴리피롤이 복합재료 내에 균일하게 침투하여 분산되어 있음을 나타내었다. DMA를 사용하여 폴리피롤과 호스트고분자와의 상용성을 조사하였으며 dynamic mechanical analysis(DMA) 분석결과 복합재료 내에서 폴리피롤의 함량이 증가되면서 상용성이 점진적으로 저하되었다.

• 분석과학
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• 제8권4호
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• pp.675-682
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• 1995

Thin films of buckminsterfullerene($C_{60}$) formed by solution drop casting on Pt foil electrode surfaces were studied by cyclic voltammetry(CV) in acetonitrile(MeCN) containing quaternary ammonium or alkali-metal salts as supporting electrolyte. The electrochemical behaviors of $C_{60}$ films are found to be strongly dependent on the nature of the supporting electrolytes, especially with tetrabutyl ammonium perchlorate (TBAP, $NBu_4ClO_4$), and tetrabutyl ammonium tetrafluoroborate ($TBABF_4$, $NBu_4BF_4$). Reasonably stable films are formed into which electrons can be injected. The interaction of $C_{60}$ film with the quaternary ammonium cation may produce the fulleride salts $(TBA^+)(C{_{60}}^-)$ and $(TBA^+)_2(C{_{60}}^{2-})$. The bulk electroreduction with a controlled potential to generate the soluble $C{_{60}}^{3-}$ anions(dark red-brown color) is followed by electrooxidative deposition to produce a neutral $C_{60}$ film on the surface. The peak currents($I_{pc}$ and $I_{pa}$) of these thin film were dramatically decreased with repetitive potential scanning. These results could be explained by the adsorption-desorption phenomena and ion pairing interaction of reduced species($C{_{60}}^-$, and $C{_{60}}^{2-}$) onto the electrode surface. The peak current changes and peak potential shifts of the thin $C_{60}$ film in cyclic voltammograms formed from solution were observed by varying scan rates.

• 한국항공우주학회지
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• 제44권7호
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• pp.576-584
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• 2016

본 연구는 다단 하이브리드 로켓의 낮은 비추력 성능을 향상시키는 방법으로 AP 첨가 추진제를 제안하고 있다. 추진제에 첨가된 AP 첨가비율 변화에 따라 다단 하이브리드 로켓의 비추력 성능 변화와 연료과농 연소특성 변화를 살펴보았으며, 이때 AP 첨가비율은 하이브리드 로켓의 연소 특징을 유지하기 위해 최대 15 wt%로 제한하였다. 결과에 의하면, AP 15 wt% 추진제는 AP 0 wt% 추진제와 비교하여 비추력 성능이 약 3% 향상되었다. 또한, 동일한 연소온도를 유지함에도 불구하고, AP 첨가비율을 증가시키면 산화제 유입량, O/F비 변화량, 그리고 연소압력은 감소하며 반경반향 온도 분포가 좋아지는 등 다단 하이브리드 로켓의 성능향상에 긍정적인 효과가 나타났다. 그러나 오직 AP를 추진제에 첨가하는 것만으로 다단 하이브리드 로켓의 비추력 성능을 일반 화학로켓의 수준으로 향상시키는 것이 매우 어려운 일임을 고려할 때, 추가적으로 금속입자 첨가를 통해 비추력 성능을 향상시킬 계획이다.