• Title/Summary/Keyword: 리간드 효과

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Thermodynamic Parameters of Complexation of Lanthanides by L-proline (Lanthanides-L-proline 착물의 형성에 관한 열역학적 연구)

  • Choi Im-Yeon;Kim Young-Inn;Choi Sung-Nak;Hyun Myung-Ho
    • Journal of the Korean Chemical Society
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    • v.37 no.1
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    • pp.105-111
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    • 1993
  • The stability constants for lanthanides complexes with optically active L-proline (1 : 1) were determined in aqueous solution in the ionic medium of 0.1 M $NaClO_4$ at 25$^{\circ}C$ using a pH titration method. The results show called "gadolinium break" between lighter and heavier lanthanides. The linear relation between the stability constant (log$\beta$1) and the pKa values of ligands indicates that L-proline acts as a bidentate ligand in the complexation. The thermodynamic parameters (${\Delta}H$ and ${\Delta}S$) were also determined using an enthalpy titration method at the same condition. The positive endothermic enthalpy change and positive entropy change clearly indicate that the driving force for the complexation is an entropy effect. The comparison of the thermodynamic parameters of L-proline complexes with anthranilate complexes supports the conclusion that the heterocyclic nitrogen atom and carboxylate of L-proline are involved in the chleate formation. The enthalpy values for L-proline are more positive than the ones for anthranilate complex. The difference in enthalpy change for the complex formation between L-proline complex and anthranilate complex is explained in terms of the basicity of the nitrogen donor atom in the ligand. The relatively large entropy change may be described by the extra dehydration related to the rigidity of L-proline ring.

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Complex Formation of Substituted Benzo-1,4,7,10,13-pentaoxacyclopentadecane (B15C5) with Nd(Ⅲ) (Nd(Ⅲ)과 치환된 Benzo-1,4,7,10,13-pentaoxacyclopentadecane (B15C5)와의 착물 형성에 관한 연구)

  • Kim, Hae-Joong;Kim, Jeong;Kim, Si-Joong
    • Journal of the Korean Chemical Society
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    • v.39 no.6
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    • pp.440-445
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    • 1995
  • The chemical compositions and stability constants, thermodynamic parameters for the neodymium(Ⅲ) complexes of substituted benzo-1,4,7,10,13-pentaoxacyclopentadecane(B15C5) have been determined by spectrophotometry and conductometry in methanol solution at various temperatures. As substituents, CH3, Br, CHO, NO2, and 3,4-(NO2)2 were used. In methanol solution the ratios of neodymium(Ⅲ) to the ligands in the complexes are 1 : 1. The stability constants were increased in order of B15C5-3,4-(NO2)2 < B15C5-NO2 < B15C5-CHO < B15C5-Br < B15C5 < B15C5-CH3. This observation can be explained in terms of the substituent effect. The order of stability constants was dimethylsulfoxide < acetone < acetonitrile in solution and the magnitudes were found to be inversely proportional to the solvents donicities. These results could be understood in terms of solvent basicity, ligand basicity, solvation of the cation, and entropy changes of complex formation.

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Preparation and Characteristics of Poly(phenylene ether)s in Various Reaction Conditions (다양한 반응조건에 따른 폴리페닐렌에테르의 중합 특성)

  • Park, Jong-Hyun;Kim, Nam-Cheol;Kim, Yong-Tae;Nam, Sung-Woo;Kim, Young-Jun;Kim, Ji-Heung
    • Polymer(Korea)
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    • v.35 no.3
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    • pp.244-248
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    • 2011
  • Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was synthesized by oxidative polymerization using various Cu(I)-amine catalyst system. The effects of catalyst/monomer ratio, different amine ligand, and the content of 2,4,6-trimethylphenol (TMP) additive on the polymer yield and molecular weight were investigated by using gel permeation chromatography. The catalytic activity of various Cu-amine systems on the 2,S-dimethylphenol (DMP) polymerization was monitored and compared each other through oxygen-uptake experiment. In addition, the effect of catalyst removal using aqueous EDTA on the thermal stability of the prepared polymer was elucidated by thermogravimetric analysis.

비피리딘계 배위자를 활용한 발광착체

  • Jeong, Hee-Sun;Kyu, Cho-Woong;Kim, Dong-Ho;Yang, Kwang-Woon;Chung, Min-Chul
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.152-152
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    • 2010
  • 본 연구에서는 인광 효과가 큰 heavy metal 인 이핵 Iridium 착체가 합성된 구조적, 광학적 및 전기적 특성을 배경으로 하였다. 가교제로는 카본 conjugated 된 리간드 bipyridine계 배위자를 사용하여 단핵 및 이핵 Platinum 착물 화합물을 합성 하였다. 합성 되어진 이핵 Platinum 착물 화합물의 화학적 구조를 결정하기 위해 $^1H(^{13}C)$-NMR, UV-vis, Spectro Photometer, MALDI TOF-MS 등을 사용하였으며, 광 물리적, 전기화학적 측정을 Spectrofluoromete, Cyclic Voltammetry를 통해 관찰 하였다.

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Optical Resolution of Dansyl Amino acids by Xylenyl-L-proline Copper (Ⅱ) Complex (Xylenyl-L-proline 구리 (Ⅱ) 착물을 이용한 단실아미노산의 광학분리)

  • Lee, Seon Haeng;O, Dae Seop;Park, Bun Ja
    • Journal of the Korean Chemical Society
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    • v.34 no.1
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    • pp.76-84
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    • 1990
  • Optical isomers of dansyl amino acids were separated by a chiral mobile phase addition method. Two metha and para isomers of xylenyl-L-proline were prepared and used as the ligands of copper(Ⅱ) chelate to resolve the dansyl amino acids. Their elution behaviors were similar to those obtained from the addition of copper (Ⅱ) benzyl-L-proline chelate. The matrix effect of the mobile phase such as pH, concentration of buffer and compositions of organic solvent acetonitrile affected the optical resolution. The separation mechanism could be explained by a cis-trans effect of the ligand exchange reaction and hydrophobic interaction between the ternary complex and the stationary phase.

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Spectroscopic Studies on U(VI) Complex with 2,6-Dihydroxybenzoic acid as a Model Ligand of Humic Acid (분광학을 이용한 흄산의 모델 리간드인 2,6-Dihydroxybenzoic acid와 우라늄(VI)의 착물형성 반응에 관한 연구)

  • Cha, Wan-Sik;Cho, Hye-Ryun;Jung, Euo-Chang
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.9 no.4
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    • pp.207-217
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    • 2011
  • In this study the complex formation reactions between uranium(VI) and 2,6-dihydroxybenzoate (DHB) as a model ligand of humic acid were investigated by using UV-Vis spectrophotometry and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The analysis of the spectrophotometric data, i.e., absorbance changes at the characteristic charge-transfer bands of the U(VI)-DHB complex, indicates that both 1:1 and 1:2 (U(VI):DHB) complexes occur as a result of dual equilibria and their distribution varies in a pH-dependent manner. The stepwise stability constants determined (log $K_1$ and log $K_2$) are $12.4{\pm}0.1$ and $11.4{\pm}0.1$. Further, the TRLFS study shows that DHB plays a role as a fluorescence quencher of U(VI) species. The presence of both a dynamic and static quenching process was identified for all U(VI) species examined, i.e., ${UO_2}^{2+}$, $(UO_2)_2{(OH)_2}^{2+}$, and $(UO_2)_3{(OH)_5}^+$. The fluorescence intensity and lifetimes of each species were measured from the time-resolved spectra at various ligand concentrations, and then analyzed based on Stern-Volmer equations. The static quenching constants (log $K_s$) obtained are $4.2{\pm}0.1$, $4.3{\pm}0.1$, and $4.34{\pm}0.08$ for ${UO_2}^{2+}$, $(UO_2)_2{(OH)_2}^{2+}$, and $(UO_2)_3{(OH)_5}^+$, respectively. The results of Stern-Volmer analysis suggest that both mono- and bi-dentate U(VI)-DHB complexes serve as groundstate complexes inducing static quenching.

Antihypertensive activity of KR-31081, an orally active nonpeptide AT1 receptor antagonist (안지오텐신 수용체 리간드 KR-31081의 생체 내 활성에 관한 연구)

  • Lee, Sung-Hou
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.11
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    • pp.3473-3479
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    • 2009
  • The pharmacological profile of KR-31081, a newly synthesized AT1 receptor antagonist, was evaluated in pithed rats, conscious renal hypertensive rats (RHRs) and conscious furosemide-treated beagle dogs. In pithed rats, KR-31081 (i.v.) induced a non-parallel right shift in the dose-pressor response curve to angiotensin II (ID50: 0.05 mg/kg) with a dose-dependent reduction in the maximum responses; this antagonistic effect was about 40 times more potent than losartan (ID50: 1.74 mg/kg) which showed competitive antagonism. KR-31081 did not alter the responses induced by other agonists such as norepinephrine and vasopressin. In RHRs, orally given KR-31081 produced a dose-dependent and long-lasting (>24 h) antihypertensive effect with a higher potency to losartan (ED20: 0.30 and 3.36 mg/kg, respectively). In furosemide-treated dogs, orally given KR-31081 produced a dose-dependent and long-lasting (>8h) antihypertensive effect with a rapid onset of action (time to Emax: 1-1.5 h) and 20-fold greater potency than losartan (ED20: 0.41 and 8.13 mg/kg, respectively). These results suggest that KR-31081 is a potent, orally active AT1 receptor antagonist useful for the research and diagnostic tools as an added exploratory potential.

Synthesis and Characterization of Molybdenum (0) Complexes with Various Alkadienes (몰리브덴늄 (0)-알카디엔화합물의 합성 및 확인)

  • Yun Sock Sung;Choi Yun Dong;Chang In Soon
    • Journal of the Korean Chemical Society
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    • v.34 no.5
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    • pp.430-437
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    • 1990
  • Various tris (${\eta}^4$-diene) molybdenums were easily synthesized by the reaction of various 1,3-dienes and molybdenum metal vapors by using metal atom reactor. The methyl substituent effect of the tris (${\eta}^4$-diene) molybdenum produced were discussed. And some alkadiene-molybdenum complexes which were easily decomposed in the air at room temperature were also formed.(C$_6$H$_{10}$)$_2$(CO)$_3$Mo were synthesized and its molybdenum-diene bond type were discussed.

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Optical Resolution of DABS-Amino Acids with Mobile Chiral Chelate Addition (키랄킬레이트 이동상첨가법에 의한 답실아미노산의 광학이성질체 분리)

  • Lee, Seon Haeng;O, Dae Seop;Byeon, Seong Gu
    • Journal of the Korean Chemical Society
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    • v.34 no.4
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    • pp.345-351
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    • 1990
  • Optical isomers of DABS-amino acids have been separated in a reversed phae high performance liquid chromatography by adding Cu (Ⅱ)-L-Proline chelate to the mobile phase. The retention behaviors for the DABS-amino acids are discussed in terms of pH of the mobile phase and the concentrations of acetonitrile, Cu (Ⅱ) complex, and buffer. The selectivity of the optical isomers of DABS-amino acids increases with the pH of the mobile, and the concentration of the chelate, but decreases with concentration of the oganic modifier. The concentration of buffer does not affect the optical separation selectivity. A separation mechanism is illustrated by cis and trans formation based on the steric effect of the ligand exchange reaction between DABS-amino acids and the copper chelate.

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Spectrophotometric Determination of Vanadium(IV) with 2-Hydroxybenzaldehyde-5-Nitro-pyridylhydrazone in the Presence of Sodium Dodecyl Sulfate (Sodium dodecyl sulfate에서 2-Hydroxybenzaldehyde-5-Nitro-pyridylhydrazone을 이용한 바나듐(IV)의 분광광도법 정량)

  • Park, Chan-Il;Jung, Young-Chul;Cha, Ki-Won
    • Analytical Science and Technology
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    • v.13 no.1
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    • pp.22-26
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    • 2000
  • 2-Hydroxybenzaldehyde-5-Nitro-pyridylhydrazone (2HB-5NPH) was synthesized and its application in the spectrophotometric determination of vanadium ion(IV) was studied in the presence of surfactant. The optimum conditions of pH, solvent effect, concentration of ligand and surfactant were evaluated. The procedure was applied to determination of vanadium (IV) in mixture sample and real sample with satisfactory results (recovery ${\geq}$ 97% ; relative standard deviation ${\leq}$ 3.0% in the concentration range of $0{\sim}1.5{\mu}g/mL$ ; detection limit, $0.02{\mu}g/mL$ in solution).

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