• Journal of the Korean Chemical Society
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• v.47 no.6
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• pp.569-577
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• 2003

Ligands, Br-PEMP, Cl-PEMP and $CH_3O-PEMP$ having Br, Cl and $CH_3O$ substituents at 5-position of the $N_2O$ tridentate ligand, 2-[(2-pyridine-2-ethylamio)-methyl]-phenol (H-PEMP) containing pyridine and phenol were synthesized. Another ligand, Naph-PEMP having pyridine and 2-hydroxy-1-naphthalene was also synthesized. The ligands were characterized using elemental analysis, UV-visible, IR, $^1H\;NMR\;and\;^{13}C$ NMR spectroscopy and mass analysis. The potentiometric titration study in aqueous solution revealed that the proton dissociation of the ligands occurred in three steps and the order of overall proton dissociation constants (log${\beta}$) was $CH_3O-PEMP$ > Naph-PEMP > H-PEMP > Cl-PEMP > Br-PEMP. The order of stability constants (logML and log$ML_2$) of their transition metal complexes was Co(II) < Ni(II) < Cu(II) > Zn(II). The order in their stability constants values of each transition metal complex agreed well with that in overall proton dissociation constant value of the ligands.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.541-550
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• 2010

A new $N_4O_3$ heptadentate ligand, N,N'-Bis(2-hydroxybenzyl)-1,3-bis[(2-aminoethyl)amino]-2-propanol(H-BAP 4HCl)was synthesized. The hydrochloric acid salts of Br-BAP 4HCl, Cl-BAP 4HCl, $CH_3O$-BAP 4HCl and $CH_3$-BAP 4HCl containing Br-, Cl-, H-, $CH_3O-$ and $CH_{3^-}$ groups at the para-site of the phenol group of the H-BAP were synthesized. The structures of the ligands were confirmed by C. H. N. atomic analysis and $^1H$ NMR, $^{13}C$ NMR, UV-visible and mass spectra. The elemental stepwise protonation constants(${logK_n}^H$) of the synthesized $N_4O_3$ ligands showed six steps of the proton dissociation. The orders of the overall dissociation constants($log{\beta}_p$) of the ligands were Br-BAP < Cl-BAP < H-BAP < $CH_3O$-BAP < $CH_3$-BAP. The orders agreed well with that of Hammett substituent constants($\sigma_p$). The calculated stability constants($logK_{ML}$) between the ligands and transition metal ions agreed well with the order of the overall proton dissociation constants of the ligands but they showed a reverse order in Hammestt substituent constants($\sigma_p$). The order of the stability constants between the transition metal ions with the ligands were Co(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II).

• Analytical Science and Technology
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• v.19 no.2
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• pp.131-141
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• 2006

Hydrobromic acid salt of a $N_2O_2$ tetradentate ligand, N,N'-bis(2-hydroxybenzyl)-ethylene-diamine ($H-BHE{\cdot}2HBr$) was synthesized. $Br-BHE{\cdot}2HBr$, $Cl-BHE{\cdot}2HBr$, $CH_3-BHE{\cdot}2HBr$ and $CH_3O-BHE{\cdot}2HBr$ having Br, Cl, $CH_3$ and $CH_3O$ substituents at 5-position of the phenol group of $H-BHE{\cdot}2HBr$ were also synthesized. $Nap-BHE{\cdot}2HBr$ having naphthalen-2-ol instead of the phenol group was also synthesized. The potentiometry study in aqueous solution revealed that the proton dissociations of the synthesized ligands occurred in four steps and the order of the calculated overall proton dissociation constants (${\log}{\beta}_p$) of each ligand was Br-BHE < Cl-BHE < H-BHE < Nap-BHE < $CH_3$-BHE < $CH_3O$-BHE. The order showed a similar trend to that of Hammett substituent constants(${\sigma}_P$). The order of the stability constants (${\log}K_{ML}$) was CO(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II). The order in their stability constants (${\log}K_{ML}$) of each transition metal complex agreed well with that of the overall proton dissociation constants (${\log}{\beta}_p$).

• Analytical Science and Technology
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• v.13 no.5
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• pp.558-564
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• 2000

Mononuclear schiff base ligand N,N'-bissalicylidene-1,2-phenylenediamine(BSPD) and binuclear schiff base ligands N,N',N',N'''-tetrasalicylidene-3,3',4,4'-tetraaminodiphenyl-methane (TSTM), N,N',N'',N'''-tetrasalicylidene-3,3'-diaminobenzidine (TSDB) have been synthesized. Proton dissociation constants of the ligands were determined by potentiometric method. The synthesized ligands and complexes formed with Cu(II) ion. These complexes were investigated by cyclic voltammetry and differential pulse voltammetry. The results revealed two step diffusion controlled redox process. The mononuclear complex Cu(II)-BSPD and binuclear complexes $Cu(II)_2$-TSDB and $Cu(II)_2$-TSTM were used in the oxidation reaction of ascorbic acid. The reaction rates were in the order of $Cu(II)_2$-TSTM>$Cu(II)_2$-TSDB>Cu(II)-BSPD, indicating that the binuclear $Cu(II)_2$-TSTM complex had the fastest values.

• Analytical Science and Technology
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• v.9 no.4
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• pp.345-354
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• 1996

Algal(II) Multidentate N, O-Schiff base ligands, such as bis(salicylaldehyde) ethylenediimine(SED), bis(salicylaldehyde) propylenediimine(SPD), bis(salicylaldehyde) diethylenetriimine(SDT), bis (salicylaldehyde) triethylenetetraimine(STT) and bis(salicyl-aldehyde)tetraethylenepentaimine(STP) were prepared. Stepwise proton dissociation constants of the Schiff base were measured potentiometrically in ethanol and a mixture of 70% dioxane and 30% $H_2O$. The stability constants of copper(II)-Schiff base complexes were in the order of Cu(II)-SPD${\leq}$Cu(II)-SED~STT${\leq}$Cu(II)-STP. Oxidation-reduction process of the Cu(II)-Schiff base complexes was involved with one-electron reaction.

• Journal of the Korean Chemical Society
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• v.44 no.5
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• pp.403-409
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• 2000

The formation and dissociation rates of $Zn^{2+}$ Complexes with l,4,7,10-tetraaza-13,16-diox-acyclooctadecane-N,N',N",N'"-tetraacetic acid (1), 1,4,7,10-tetraaza-13,16- dioxacyclooctadecane-N,N',N",N'"-tetramethylacetic acid (2), and 1,4,7,10-tetraaza-13,16- dioxacyclooctadecane-N,N',N",N'"-tetrapropionic acid(3) have been measured by stopped-flow and conventional spectrophotometry. Observations were made at 25.0$\pm$0.1 $^{\circ}C$ and at an ionic strength of 0.10 M NaClO$_4$. The formation reactions of $Zn^{2+}$ ion with 1 and 2 took place by the rapid formation of an intermediate complex (ZnH$_3L^+$) in which the $Zn^{2+}$ ion is incompletely coor-dinated. This might then lead to be a final product in the rate-determining step.ln the pH range 4.76-5.76, the diprotonated (H2L2-) form is the kinetically active species despite of its low concentration. The stability con-stants (log$K_{(ZnH$_3$3$L^+$)}$) and specific water-assisted rate constants (koH) of intermediate complexes have been deter-mined from the kinetic data. The dissociation reactions of $Zn^{2+}$ complexes of 1,2, and 3 were investigated with $Cu^{2+}$ ions as a scavenger in acetate buffer. All complexes exhibit acid-independent and acid-catalyzed con-tributions. The effect of buffer and $Cu^{2+}$ concentration on the dissociation rate has also been investigated. The ligand effect on t dissociation rate of $Zn^{2+}$ complexes is discussed in terms of the side-pendant armsand the chelate ring sizes of the ligands.

• Applied Biological Chemistry
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• v.48 no.2
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• pp.115-119
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• 2005

The catalytic hydrolysis reactivities of dinuclear nickel (II) complex, ${\mu}-aquapentaaqua[{\mu}-3,6-bis(6'-methyl-2'-pyridyl)pyridazine]chlorodinickel\;(II)$ trichloride trihydrate (APNT) for bis(p-nitrophenyl) phosphate (BNPP) as a DNA model compound were investigated. The dissociation constants of APNT were $pKa_1=7.9$ and $pKa_2=9.6$, respectively. The hydrolysis rate constant of BNPP compound by APNT was showed the rate enhancement of about 370,000 times in the case of none catalyst at pH 7.0 and $50^{\circ}C$. Based on the findings, we proposed the catalytic cycle for the hydrolysis of BNPP by APNT complex. The metal ions of dinuclear nickel (II) complex significantly enhance the transfer rate of phosphoryl group in the catalytic process and the water molecules as nucleophile and proton transfer agent act in different steps.