Extensive inhibition by ion pairing in a bimolecular, outer-sphere electron transfer reaction, reduction of a cobalt clathrochelate by ferrocene in methylene chloride

Pfeiffer, J.; Kirchner, Karl; Wherland, Scot

doi:10.1016/s0020-1693(00)00362-5

Cited by 7 publications

(3 citation statements)

References 15 publications

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“…Beyond the phase transition temperature, the rate of the reaction increases with an increase in the concentration of DPPC, which is ascribed to the release of the cobalt(III) complex from the interior to the exterior surface of the DPPC membrane. As a consequence, the intervesicular hydrophobic interaction between vesicles surface and hydrophobic part of the surfactant cis-[Co (dmp) 2 3 . The linearity of the isokinetic plots of these complexes corroborates that the existence of a common mechanism exists with respect to the change of initial concentration of complexes.…”

Section: Discussionmentioning

confidence: 99%

“…[2] The alteration of the outer-sphere environment of metal complex caused by the variation of concentration of the counter ions [3] has an influence on electron transfer reactions. Recently, there has been a growing interest in the study of electron transfer reactions in microheterogeneous environment, [4À9] where one or more of the reactants are forced to remain at the surface of micelles, [10,11] or in the cavity of cyclodextrins [12,13] and related compounds, or at the surface of DNA, [14,15] etc.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and mechanism of electron transfer reaction of single and double chain surfactant cobalt(III) complex by Fe²⁺ions in liposome (dipalmitoylphosphotidylcholine) vesicles: effects of phase transition

Nagaraj

Murugan²,

Thangamuniyandi

2015

Phase Transitions

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In this study, we report the kinetics of reduction reactions of single and double chain surfactant cobalt(III) complexes of octahedral geometry, cis-[Co(en) 2 (4AMP)(DA)] (ClO 4 ) 3 and cis-[Co(dmp) 2 (C 12 H 25 NH 2 ) 2 ](ClO 4 ) 3 (en D ethylenediamine, dmp D 1,3-diaminopropane, 4AMP D 4-aminopropane, C 12 H 25 NH 2 D dodecylamine) by Fe 2C ion in dipalmitoylphosphotidylcholine (DPPC) vesicles at different temperatures under pseudo first-order conditions. The kinetics of these reactions is followed by spectrophotometry method. The reactions are found to be second order and the electron transfer is postulated as outer sphere. The remarkable findings in the present investigation are that, below the phase transition temperature of DPPC, the rate decreases with an increase in the concentration of DPPC, while above the phase transition temperature the rate increases with an increase in the concentration of DPPC. The main driving force for this phenomenon is considered to be the intervesicular hydrophobic interaction between vesicles surface and hydrophobic part of the surfactant complexes. Besides, comparing the values of rate constants of these outer-sphere electron transfer reactions in the absence and in the presence of DPPC, the rate constant values in the presence of DPPC are always found to be greater than in the absence of DPPC. This is ascribed to the double hydrophobic fatty acid chain in the DPPC that gives the molecule an overall tubular shape due to the intervesicular hydrophobic interaction between vesicles surface and hydrophobic part of the surfactant complexes more suitable for vesicle aggregation which facilitates lower activation energy, and consequently higher rate is observed in the presence of DPPC. The activation parameters (DS # and DH # ) of the reactions at different temperatures have been calculated which corroborate the kinetics of the reaction.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetics and mechanism of electron transfer reaction of single and double chain surfactant cobalt(III) complex by Fe²⁺ions in liposome (dipalmitoylphosphotidylcholine) vesicles: effects of phase transition

Nagaraj

Murugan²,

Thangamuniyandi

2015

Phase Transitions

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“…The electron transfer based on the outer sphere among first-row metal complexes plays a vital role both in vivo [ 5 ] and in the treatment of molecular-scale devices, such as logic gates and molecular wires [ 7 ]. The alterations of the electron transfer reactions on the outer-sphere environment complex are attributable to the variation of counter ion concentrations [ 8 ]. Gaswick et al have reported that the [Fe(CN) 6 ] 4− can reduce some pentamminecobalt(III) complexes to cobalt(II) via an outer-sphere electron transfer step [ 9 ] and they have also reported that the substituted pentamminecobalt(III) complexes could be reduced by [Fe(CN) 6 ] 4− with the development of an ion pair [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

States of Aggregation and Phase Transformation Behavior of Metallosurfactant Complexes by Hexacyanoferrate(II): Thermodynamic and Kinetic Investigation of ETR in Ionic Liquids and Liposome Vesicles

Nagaraj¹,

Sakthinathan

Chiu

et al. 2022

Biomimetics

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Electronic absorption spectroscopy was used to study the ETR of surfactant–cobalt(III) complexes containing imidazo[4,5-f][1,10]phenanthroline, dipyrido[3,2-d:2′-3′-f]quinoxaline and dipyrido[3,2-a:2′,4′-c](6,7,8,9-tetrahydro)phenazine ligands by using ferrocyanide ions in unilamellar vesicles of dipalmitoylphosphotidylcholine (DPPC) and 1-butyl-3-methylimidazolium bromide ((BMIM)Br), at different temperatures under pseudo-first-order conditions using an excess of the reductant. The reactions were found to be second-order and the electron transfer is postulated as occurring in the outer sphere. The rate constant for the electron transfer reactions was found to increase with increasing concentrations of ionic liquids. Besides these, the effects of surfactant complex ions on liposome vesicles in these same reactions have also been studied on the basis of hydrophobicity. We observed that, below the phase transition temperature, there is an increasing amount of surfactant–cobalt(III) complexes expelled from the interior of the vesicle membrane through hydrophobic effects, while above the phase transition temperature, the surfactant–cobalt(III) complexes are expelled from the interior to the exterior surface of the vesicle. Kinetic data and activation parameters are interpreted in respect of an outer-sphere electron transfer mechanism. By assuming the existence of an outer-sphere mechanism, the results have been clarified based on the presence of hydrophobicity, and the size of the ligand increases from an ip to dpqc ligand and the reactants become oppositely charged. In all these media, the ΔS# values are recognized as negative in their direction in all the concentrations of complexes employed, indicative of a more ordered structure of the transition state. This is compatible with a model in which these complexes and [Fe(CN)6]4− ions bind to the DPPC in the transition state. Thus, the results have been interpreted based on the self-aggregation, hydrophobicity, charge densities of the co-ligand and the reactants with opposite charges.

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The outer-sphere association of p-sulfonatothiacalix[4]arene with some Co(III) complexes: the effect on their redox activity in aqueous solutions

Mustafina

Штырлин

Zakharova

et al. 2007

J Incl Phenom Macrocycl Chem

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Extensive inhibition by ion pairing in a bimolecular, outer-sphere electron transfer reaction, reduction of a cobalt clathrochelate by ferrocene in methylene chloride

Cited by 7 publications

References 15 publications

Kinetics and mechanism of electron transfer reaction of single and double chain surfactant cobalt(III) complex by Fe²⁺ions in liposome (dipalmitoylphosphotidylcholine) vesicles: effects of phase transition

Kinetics and mechanism of electron transfer reaction of single and double chain surfactant cobalt(III) complex by Fe²⁺ions in liposome (dipalmitoylphosphotidylcholine) vesicles: effects of phase transition

States of Aggregation and Phase Transformation Behavior of Metallosurfactant Complexes by Hexacyanoferrate(II): Thermodynamic and Kinetic Investigation of ETR in Ionic Liquids and Liposome Vesicles

The outer-sphere association of p-sulfonatothiacalix[4]arene with some Co(III) complexes: the effect on their redox activity in aqueous solutions

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Extensive inhibition by ion pairing in a bimolecular, outer-sphere electron transfer reaction, reduction of a cobalt clathrochelate by ferrocene in methylene chloride

Cited by 7 publications

References 15 publications

Kinetics and mechanism of electron transfer reaction of single and double chain surfactant cobalt(III) complex by Fe2+ions in liposome (dipalmitoylphosphotidylcholine) vesicles: effects of phase transition

Kinetics and mechanism of electron transfer reaction of single and double chain surfactant cobalt(III) complex by Fe2+ions in liposome (dipalmitoylphosphotidylcholine) vesicles: effects of phase transition

States of Aggregation and Phase Transformation Behavior of Metallosurfactant Complexes by Hexacyanoferrate(II): Thermodynamic and Kinetic Investigation of ETR in Ionic Liquids and Liposome Vesicles

The outer-sphere association of p-sulfonatothiacalix[4]arene with some Co(III) complexes: the effect on their redox activity in aqueous solutions

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Kinetics and mechanism of electron transfer reaction of single and double chain surfactant cobalt(III) complex by Fe²⁺ions in liposome (dipalmitoylphosphotidylcholine) vesicles: effects of phase transition

Kinetics and mechanism of electron transfer reaction of single and double chain surfactant cobalt(III) complex by Fe²⁺ions in liposome (dipalmitoylphosphotidylcholine) vesicles: effects of phase transition