• Journal of Integrative Natural Science
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• v.7 no.3
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• pp.188-192
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• 2014

Determination of cobalt(III) ion with a perfluorinated sulfonated polymer-ethylenediamine (nafion-en) modified glassy carbon electrode is studied. It is based on the chemical reactivity of an immobilized layer, nafion-en, to yield complex $[Co(en)_3]^{3+}$. The reduction peak potential by differential pulse voltammetry (DPV) is observed at $-0.437{\pm}0.047$ V (vs. Ag/AgCl). The linear calibration curve is obtained in cobalt(III) ion concentration range $1.0{\times}10^{-8}{\sim}1.0{\times}10^{-3}M$ ($5.893{\times}10^{-12}{\sim}5.893{\times}10^{-5}g/mL$).

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1581-1585
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• 2012

Two pyridinecarboxamide dicyanidecobalt(III) building blocks and two mononuclear seven-coordinated macrocycle manganese(II) compounds have been rationally selected to assemble cyanide-bridged heterobimetallic complexes, resulting in three cyanide-bridged $Co^{III}-Mn^{II}$ complexes. Single X-ray diffraction analysis show that these complexes $\{[Mn(L^1)][Co(bpb)]\}ClO_4{\cdot}CH_3OH{\cdot}0.5H_2O$ ($\mathbf{1}$), $\{[Mn(L^2)][Co(bpb)]\}ClO_4{\cdot}0.5CH_3OH$ ($\mathbf{2}$) and ${[Mn(L^1)][Co(bpb)]\}ClO_4{\cdot}H_2O$ ($\mathbf{3}$) ($L^1$ = 3,6-diazaoctane-1,8-diamine, $L^2$ = 3,6-dioxaoctano-1,8-diamine; $bpb2^{2-}$ = 1,2-bis(pyridine-2-carboxamido)benzenate, $bpmb2^{2-}$ = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate) all present predictable one-dimensional single chain structures. The molecular structures of these one-dimensional complexes consists of alternating units of $[Mn(L)]^{2+}$ ($L=L^1$ or $L^2$) and $[Co(L^{\prime})(CN)2]^-$ ($L^{\prime}=bpb2^{2-}$, or $bpmb2^{2-}$), forming a cyanide-bridged cationic polymeric chain with free $ClO_4{^-}$ as the balance anion. The coordination geometry of manganese(II) ion in the three one-dimensional complexes is a slightly distorted pentagonal-bipyrimidal with two cyanide nitrogen atoms at the trans positions and $N_5$ or $N_3O_2$ coordinating mode at the equatorial plane from ligand $L^1$ or $L^2$. Investigation over magnetic properties of these complexes reveals that the very weak magnetic coupling between neighboring Mn(II) ions connected by the diamagnetic dicyanidecobalt(III) building block. A best-fit to the magnetic susceptibility of complex ${\mathbf}{1}$ leads to the magnetic coupling constants $J=-0.084(3)cm^{-1}$.

• Journal of the Korean Chemical Society
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• v.28 no.6
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• pp.384-392
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• 1984

Reaction of the Fe(II) complex of a fully saturated tetradentate macrocyclic ligand [Fe([14]aneN$_4)(CH_3CN)_2]^{2+}$, where [14]ane$N_4$ represents 1,4,8,11-tetraazacyclotetradecane, with $O_2$ has been investigated in acetonitrile solutions. [Fe([14]aneN$_4)(CH_3CN)_2]^{2+}$ reacts with oxygen to yield low spin Fe(III) species, [Fe([14]aneN$_4)(CH_3CN)_2]^{3+}$, which undergoes metal ion assisted oxidative dehydrogenation of the macrocyclic ligand to produce low spin Fe(II) complex, [Fe([14]tetraeneN$_4)(CH_3CN)_2]^{2+}$. The macrocyclic ligand in [Fe([14]tetraeneN$_4)(CH_3CN)_2]^{2+}$ is highly unsaturated and its double bonds are conjugated. [Fe([14]dieneN$_4)(CH_3CN)_2]^{2+}$ and [Fe([14]dieneN$_4)(CH_3CN)_2]^{3+}$ are isolated as the intermediates of the reaction. The Fe(II) complexes involved in this oxidative dehydrogenation reaction react with carbon monoxide to give respective carbon monoxide derivatives, [FeL$(CH_3CN)(CO)]^{2+}$ (where L = macrocyclic ligand). The values of $v_{CO}$ of [FeL$(CH_3CN)(CO)]^{2+}$, and the electrochemical oxidation potentials of Fe(II) ${\to}$ Fe(III) and the qualitative stability toward air-oxidation for [FeL(CH$_3CN_2)^{2+}$ increase as the degree of unsaturation of the macrocyclic ligands increase.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.225-231
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• 1989

The heterogeneous rate constants for the electrochemical reduction by $trans-[Co(en)_2X_2](ClO_4)_n$(where X is cyanide, nitrite, ammonia, and isothiocyanate) at mercury and glassy carbon electrode were investigated by cyclic voltammetry, DC polarography, and by using rotating disk electrode. The good linear relationship was obtained between the activation energy of reduction and absorption wave number of complexes on glassy carbon electrode. At mercury electrode, $NO_2^-$ ligated complex showed the large deviation from the linear relationship. The difference in the value of rate constants for $NO_2^-$ ligated complex between mercury and glassy carbon electrode was about three order of magnitude which was much larger than the other complexes. It was suggested that $NO_^-$ ligated complex was reduced by inner-sphere mechanism on mercury electrode from the larger value of activation energy and entropy on mercury than carbon electrode.

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.295-303
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• 1989

Tetradentate Schiff base cobalt(II) complex; Co(SND) and Co(SOPD) were synthesized, and these complexes were allowed to react with dry oxygen to form oxygen adducts cobalt(III) complexes such as $[Co(SND)(Py)]_2O_2$ and $[Co(SOPD)(Py)]_2O_2$ in pyridine. These complexes have been identified by IR specta, T.G.A., magnetic susceptibilities measurements and elemental analysis. It has been found that the oxygen adducts coblat(III) complexes have hexacoordinated octahedral configuration with tetradentate Schiff base cobalt(II), pyridine and oxygen, and the mole ratio of oxygen to cobalt(II) complexes are 1;2. The redox reaction processes of $Co(SND)(Py)_2$ and $Co(SOPD)(Py)_2$ complexes were investigated by cyclic voltammetry with glassy carbon electrode in 0.1M TEAP pyridine. The result of redox reaction processes of Co(III)/Co(II) and Co(II)/Co(I) for $Co(SND)(Py)_2$ and $Co(SOPD)(Py)_2$ complexes are reversible or quasi reversible process but oxygen adducts complexes are irreversible processes. Redox process for oxygen of oxygen adducts complexes was quasi reversible and redox range of potential was $E_{pc}\;=\;-0.96{\sim}-1.03V$ and $E_{pa}\;=\;-0.78{\sim}-0.80V.$

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.273-280
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• 1989

The spectra of the $Co^{II}CyDTA$(CyDTA: cyclohexyldiaminetetraacetic acid) complex have been measured in aqueous solution of pH = 6-13.2. The red shift of the spectrum in the more basic solution was ascribed to the transformation of $CoCyDTA^{2-}$ into $CoCyDTA(OH)^{3-}$. The equilibrium constant, $K_{OH} = [CoCyDTA(OH)^{3-}]/[CoCyDTA^{2-}][OH^-]$ was $75M^{-1}$ at $40^{\circ}C$. The electron transfer reactions of $CoCyDTA^{2-}$ and $CoCyDTA(OH)^{3-}$ with $Fe(CN)_6^{3-}$ have been studied using spectrophotometric technique in the range of pH applied to the determination of equilibrium constant. The pseudo first-order rate constants observed ($k_{obs}$) were not changed upto pH = 10.8, but increased with increasing pH in the range of pH = $10.8{\sim}13.0$. The rate law reduced in the range of pH = 6-13 was $k_{obs} = (k_3[CoCyDTA^{2-}] + k_4[CoCyDTA(OH)^{3-}])/(1+K_1[CoCyDTA^{2-}])$. The rate constants of the reactions (3a) and (3b), $k_3$ and $k_4$ respectively have been determined to be 0.529 and $4.500M^{-1}sec^{-1}$ at $40^{\circ}C$. The activation entropies (147{\pm}1.1JK^{-1} mol^{-1}$ at pH = 10.8) and activation volumes $(6.25cm^3mol^{-1}, pH = 10.8)$ increased with increasing pH, while the activation enthalpy (12.44 ${\pm}$ 0.20 kcal/mole) was independent of pH. Using the pH effect on the rate constants, the activation entropies and the activation volumes, the mechanism of the electron transfer reaction for $Co^{II}-Fe^{III}$ system was discussed.

• Journal of the Korean Chemical Society
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• v.40 no.5
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• pp.302-307
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• 1996

Diethanolamine dithiocarbamate is known to react with dichlorobis(ethylenediamine)cohalt(Ⅲ) chloride to form [Co(dtc)3](dtc=diethanolamine dithiocarbamate) in which two sulfur atoms of the dithiocarbamate are bound to cobalt. The complex is moderately soluble in acetone, but sparingly soluble in carbon disulfide. Kinetics and mechanisms of the reaction of dichlorobis(ethylenediamine)cobalt(Ⅲ) chloride with diethanolamine dithiocarbamate have been studied in aqueous solution. Activation parameters have been calculated from the kinetic data for the reaction and from these results a possible mechanism for the reaction has been proposed.

• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1771-1777
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• 2009

The homogeneous B$F_3$ containing chiral Co(III) salen complexes were anchored non-covalently on the surfaces of mesoporous SBA-16 silica containing aluminum species. The Brönsted and Lewis acidic sites are attributed to the immobilization of fluorine functionalized chiral salen complexes on the supports. The FT-IR, UV, ESCA, and NMR analyses were performed to determine the structure of synthesized chiral salen catalysts. These heterogeneous catalysts could be applied in asymmetric ring opening of terminal epoxides by water and phenol derivatives. They showed very high enantioselectivity and yield more than 98% in the catalytic synthesis of optically active products.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.829-834
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• 2010

Ligand variation was carried out on a cobalt(III) complex of Salen-type ligand comprised of 1,2-cyclohexenediamine and salicylaldehyde bearing a methyl substituent on 3-position and -[$CMe(CH_2CH_2CH_2N^+Bu_3)_2$] on 5-position, which is a highly active catalyst for $CO_2$/propylene oxide copolymerization. Replacement of the methyl substituent with bulky isopropyl group resulted in alteration of the binding mode, consequently lowering turnover frequency significantly. Replacement with an ethyl group preserved binding mode and activity. Replacement of the tributylammonium unit with trihexylammonium or trioctylammonium, or replacement of 1,2-cyclohexenediamino unit with -$NC(Me)_2CH_2N$- decreased activity, even though the binding mode was unaltered.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.511-517
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• 2002

The complex 1 $([Cp*Fe(CO)_2]_2-(\mu-CH=CH-CH=CH))$ which have butadiene as a bridge were synthesized from $Cp*(CO)_2FeK$ and cis-3,4-dichlorocyclobutene. The derivatives of complex 1 where one or two carbonyl groups are replaced by phosphine ligands have been prepared by photochemical substitution. The new derivatives $([Cp*Fe(L)_2]_2-(\mu-CH=CH-CH=CH))$ where L = $(Ph_2PCH_2CH_2PPh_2)$ and $([Cp*Fe(CO)(L)]_2-(\mu-CH=CH-CH=CH))$ where L : $PPh_3$ have been characterized from $^^1H-$, $^^13C-$,$^^31P-NMR$ and elemental analysis. Obtained complexes have been studied in electrochemical experiment and UV/VIS-near-IR. The mixed-valence radical cation forms of complex 2, 3 species were found to be delocalized as the Class III. Based on the separation of the waves ($\triangle E$ : 0.470 ~ 0.605 V), the efficiency of electronic communication between two metal centers of cation species leading to stabilization relative to neutral species. The phosphine-substitute complexes (2, 3) displays two reversible oxidation waves and oxidation state of metal centers-dependent color change, electrochromism, was observed from yellow to orange and deep blue in methylene chloride.