• Bulletin of the Korean Chemical Society
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• 제30권5호
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• pp.1143-1146
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• 2009

[$Mn_{12}O_{12}(azo-L)_{16}(H_2O)_4$] (1), a new Mn12 single molecule magnet containing a photochromic azobenzene ligand, has been successfully synthesized by substitution of acetate ligand of Mn12 with 6-[4-{4-hexyloxyphenyl( azo)}-phenoxy]hexanoic-1-acid. The reversible photoisomerization of the azobenzene group was confirmed by UV-visible absorption spectroscopy. The temperature and field dependence of dc susceptibility and the temperature and the frequency dependence of ac susceptibility were measured for the cis and the trans isomer of 1. The magnetization value of the cis isomer in dc measurement is higher than that of the trans isomer. The cis isomer of 1 has a slower relaxation because cis-trans photoisomerization of the azobenzene group in peripheral ligands induces changes in its structure and dipole moment.

• Bulletin of the Korean Chemical Society
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• 제20권4호
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• pp.436-440
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• 1999

The highly resolved absorption spectra of mer-[Cr(dpt)(Gly-Gly)]ClO4·H2O [dpt = di(3-aminopropyl)amine, H2Gly-Gly = glycylglycine] have been measured between 13000 cm-1 and 50000 cm-1 temperatures down to 2 K. The vibrational intervals were extracted by recording emission and far-infrared spectra. The characteristic infrared bands in meridional isomer were discussed. The four-teen electronic origins due to spin-allowed and spin-forbidden transitions were assigned. With the use of this electronic transitions, a ligand field optimization based on the exact known ligand geometry have been performed to determine more detailed bonding properties of Gly-Gly and dpt ligands. It is confirmed that the peptide nitrogen of the Gly-Gly has a weak π-donor property toward chrornium(Ⅲ) ion.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권4호
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• pp.23-30
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• 2011

Risk based pollution level of Pb and Cd in metal contaminated soils depending on physicochemical properties of soil in a target site was assessed using biotic ligand model. Heavy metal activity in soil solution defined as exposure activity (EA) was assumed to be toxic to Vibrio fischeri and soil organisms. Predicted effective activity (PEA) determined by biotic ligand model was compared to EA value to calculate risk quotient. Field contaminated soils (n = 10) were collected from a formes area and their risk based pollution levels were assessed in the present study using the calculated risk quotient. Concentrations of Pb determined by aqua regia were 295, 258, and 268 mg/kg in B, H and J points and concentrations of Cd were 4.73 and 6.36 mg/kg in G and I points, respectively. These points exceeded the current soil conservation standards. However, risk based pollution levels of the ten points were not able to be calculated because concentrations of Pb and Cd in soil solution were smaller than detection limits or one (i.e., non toxic). It was because heavy metal activity in soil solution was dominant toxicological form to organisms, not a total heavy metal concentration in soil. In addition, heavy metal toxicity was decreased by competition effect of major cations and formation of complex with dissolved organic carbon in soil solution. Therefore, it is essential to consider site-specific factors affecting bioavailability and toxicity for estimating reliable risk of Pb and Cd.

• 대한화학회지
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• 제44권3호
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• pp.194-199
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• 2000

The chemical behavior for Mo(0) and W(0) complexes, [M(CO)$_2$(PPh$_3$)$_4$] (M=Mo and W),has been investigated by UV-vis spectroscopic, magnetic, and electrochemical methods. Three absorption bands are observed in the UV-spectra. The crystal-field-splitti ng energy, spin-pairing energy, and bond strengths were deduced from the spectra. The metal d electrons in both complexes seemed to be delocalized in low-spin state.Metal ligand correlation appeared to strongly depend on bond strengths and diamagnetic properties. In electrochemical processes, both complexes exhibit an irreversible reduction wave.

• 대한화학회지
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• 제40권10호
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• pp.649-655
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• 1996

유기 리간드 tetramethylenesulfoxide(TMSO)을 Pd(II)와 Pt(II)의 착물들에 대한 거동을 UV-vis 분광학적, 자기적, 그리고 전기화학적 방법에 의해 조사하였다. 이들 착물들의 스펙트라에서 두 개의 에너지 흡수 띠가 관찰되었다. 결정장 갈라짐 에너지와 스핀 짝지움 에너지 그리고 결합 세기는 착물들의 스펙트라로부터 얻었다. 착물들의 전자적 성질은 비편재화이고, 낮은 스핀 상태임을 알았다. 리간드와 금속들은 강한 결합세기 였다. 이들 착물들은 반자기성 이었다. 착물들의 산화${\cdot}$환원 반응과정은 비수용매 속에서 순환${\cdot}$전압 전류법에 의해 조사하였다. 착물들의 산화${\cdot}$환원 과정은 일전자 일단계 반응이었으며, 확산과 반응 지배적 이었다.

• Bulletin of the Korean Chemical Society
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• 제24권3호
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• pp.269-273
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• 2003

The synthesis and properties of 2,13-bis(3'-pyridylmethyl) $(L^3)$, 2,13-bis(4'-pyridylmethyl) $(L^4)$, and 2,13-bis(phenylmethyl) $(L^5)$ derivatives of 5,16-dimethyl-2,6,13,17-tetraazatrcyclo$[16.4.0.^{1.18}0^{7.12}]$docosane are reported. The 3- or 4-pyridylmethyl groups of $[ML^3](ClO_4)_2\;or\;[ML^4](ClO_4)_2$ (M = Ni(Ⅱ) or Cu(Ⅱ)) are not involved in coordination, and the coordination geometry (square-planar) and ligand field strength of the complexes are quite similar to those of $[ML^5](ClO_4)_2$, bearing two phenylmethyl pendant arms. However, the complex formation reactions of $L^3\;and\;L^4$ are strongly influenced by the pyridyl groups, which can interact with a proton or metal ion outside the macrocyclic ring. The macrocycle $L^5$ exhibits a high copper(Ⅱ) ion selectivity against nickel(Ⅱ) ion; the ligand readily reacts with copper(Ⅱ) ion to form $[CuL^5]^{2+}$ but does not react with hydrated nickel(Ⅱ) ion in methanol solutions. On the other hand, $L^3\;and\;L^4$ form their copper(Ⅱ) and nickel(Ⅱ) complexes under a similar condition, without showing any considerable metal ion selectivity. The ligands $L^3\;and\;L^4$ react with copper(Ⅱ) ion more rapidly than does $L^5$ at pH 6.4. At pH 5.0, however, the reaction rate of the former macrocycles is slower than that of the latter. The effects of the 3- or 4-pyridylmethyl pendant arms on the complex formation reaction of $L^3\;and\;L^4$ are discussed.

• The Korean Journal of Ceramics
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• 제5권2호
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• pp.165-170
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• 1999

The strain sensing properties of th system xNiO-(1-x) CaO with various compositions (x=0.001-0.05) are evaluated and the origin of the phenomena is guessed. We have found out that the high temperature electrical conductivity of the xNiO-(1-x)CaO increases by applying the compressive stress at $1000^{\circ}C$. When the applied load is removed, the electrical conductivity rapidly decreases and returns to the original value, but a small hysteresis of the stress-conductivity curve is observed. After the loading test, the lattice parameter of the specimen is found lengthened. The correlation between the lengthening of the lattice parameter and the increases in the electrical conductivity by loading is discussed. The amount of the "expanded type" Ni(II)O6 clusters in the xNiO-(1-x)CaO grains is supposed to be increased by the applied stress, which would be the origin of the strain dependent electric conduction in the xNiO-(1-x)CaO system.aO system.

• 한국미생물·생명공학회지
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• 제49권1호
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• pp.65-74
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• 2021

Serine proteases are the most versatile proteolytic enzymes with tremendous applications in various industrial processes. This study was designed to investigate the biochemical properties, critical residues, and the catalytic potential of alkaline serine protease using in-silico approaches. The primary sequence was analyzed using ProtParam, SignalP, and Phyre2 tools to investigate biochemical properties, signal peptide, and secondary structure, respectively. The three-dimensional structure of the enzyme was modeled using the MODELLER program present in Discovery Studio followed by Molecular Dynamics simulation using GROMACS 5.0.7 package with CHARMM36m force field. The proteolytic potential was measured by performing docking with casein- and keratin-enriched residues, while the effect of the inhibitor was studied using phenylmethylsulfonyl fluoride, (PMSF) applying GOLDv5.2.2. Molecular weight, instability index, aliphatic index, and isoelectric point for serine protease were 39.53 kDa, 27.79, 82.20 and 8.91, respectively. The best model was selected based on the lowest MOLPDF score (1382.82) and DOPE score (-29984.07). The analysis using ProSA-web revealed a Z-score of -9.7, whereas 88.86% of the residues occupied the most favored region in the Ramachandran plot. Ser327, Asp138, Asn261, and Thr326 were found as critical residues involved in ligand binding and execution of biocatalysis. Our findings suggest that bioengineering of these critical residues may enhance the catalytic potential of this enzyme.

• 대한화학회지
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• 제34권2호
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• pp.143-158
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• 1990

본 연구에서는 동공의 크기가 다른 5종의 crown ether과 9종의 crownand계와 1종의 cryptand계 거대고리 리간드를 포함하는 우라늄(Ⅵ), 토륨(Ⅳ) 및 네오디뮴(Ⅲ), 사마륨(Ⅲ), 홀뮴(Ⅲ) 등의 희토류 금속착물을 합성 후, 고체착물의 조성식을 결정하고 적외선 스펙트럼에 의하여 구조를 확인한 다음 핵자기공명 분광법에 의하여 착물용액의 조성비와 분자내의 착물형성 site를 결정하고 착물들의 용매화 현상과 리간드 교환반응성을 핵자기공명 분광법으로 고찰하였다. crown ether 거대고리 리간드들은 실험에 사용한 모든 금속이온과 안정한 착물을 형성하므로 OCH2 메틸렌 양성자들은 모두 낮은 자기장 방향으로 화학적 이동을 나타냈으며 같은 금속이온에 대한 화학적 이동값은 12C4＜15C5＜18C6의 순으로 증가하였고 같은 리간드에 대한 희토류 착물의 화학적 이동값은 원자번호 크기에 반비례하였다. crownand 22는 우라늄(Ⅵ)과 산소 및 질소원자를 배위하는 안정한 착물을 형성하지만 희토류 금속과는 착물을 형성하지 않았다. 반면에 희토류 금속(Ⅲ)이온은 cryptand 221리간드와 모든 산소 및 질소원자를 배위자로 하는 안정한 착물을 형성할 수 있었다. 나머지 질소와 산소원자를 포함한 crownand 계열 거대고리 리간드는 우라늄(Ⅵ)과 역시 모든 산소 및 질소가 배위하는 착물을 형성하지만 희토류 금속(Ⅲ)과는 착물을 형성하지 않음을 확인할 수 가 있었다. 우라늄(Ⅵ)과 희토류(Ⅲ)금속이온은 모든 거대고리 리간드와 1:1착물을 각각 형성하며 토륨(Ⅳ)이온은 12C4와 1:2 나머지 리간드와는 1:1착물을 각각 형성함을 알 수 있었다. 이들 거대고리 리간드 착물들의 안정성은 착물의 양성자 이동결과에 잘 일치하였다. 그리고 18C6와 물을 리간드로 하는 희토류 금속(Ⅲ) 착물은 아세틸아세톤 용매내에서 리간드 교환반응이 일어나지만 우라늄(Ⅵ)착물의 경우에는 교환반응이 일어나지 않았다.

• 한국결정성장학회지
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• 제17권1호
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• pp.35-40
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• 2007

스컬(skull)용융법에 의해 성장시킨 코발트($Co^{2+}$)가 도핑(doping)된 $25{\sim}50wt%$의 서로 다른 $Y_2O_3$ 함량을 가진 이트리아 안정화 큐빅지르코니아(YSZ) 단결정을 $N_2$ 분위기 $1000^{\circ}C$에서 5시간 동안 열처리하였다. 적갈색의 단결정들은 각각 보라색 또는 청색으로 변화되었으며, Co가 첨가(doping) 된 처리 전 후의 YSZ들은 직경 6.5, 두께 2 mm의 웨이퍼 또는 직경 10 mm의 라운드브릴리언트 컷(round brilliant cut)으로 연하 하였으며, 광학적 또는 구조적 특성은 UV-VIS 분광광도계와 XRD(X-ray diffraction)로 측정하였으며, $Co^{2+}\;(^4A_2(^4F)\to{^4P})$ 및 $Co^{3+}$에 의한 흡수, 에너지 간격(energy gap) 및 격자 매개 변수(lattice parameter)변화가 분석되었다.