On the effect of ion pairing of Keggin type polyanions with quaternary ammonium cations on redox potentials in organic solvents

Bo Chen, Ronny Neumann

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Abstract

The electrochemical properties of Keggin type polyoxometalates Qn[XW12O40] (X = P, Si, B; Q = n-tetraoctylammonium and n-trioctylmethylammonium) in organic solvents were investigated in order to understand the interrelation between the redox potentials, solvents and ion pairing. A logarithmic correlation between the dielectric constant of the solvent (ϵ ranged from 4.8 to 46.6) and the reduction potential of the [PW12O4]3-/[PW12O4]4- couple was found. This reduction potential increased significantly when the surface charge of the polyoxometalate went from 3- to 5-. The investigation of the ion pairing properties by diffusion NMR revealed the presence of intimate ion pairs in less polar solvents (e.g. dichloromethane) and less compact ion pairs in more polar solvents (e.g. DMSO). Using a V atom within the polyoxometalate an NMR experiment showed that a n-trioctylmethyl ammonium cation bonded to the polyoxometalate anion more intimately than a n-tetraoctyl ammonium cation.

Original languageEnglish
Pages (from-to)22487-22493
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume18
Issue number32
DOIs
Publication statusPublished - 2016

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Ammonium Compounds
Organic solvents
Cations
Ions
cations
ions
Nuclear magnetic resonance
Methylene Chloride
Surface charge
Dimethyl Sulfoxide
Electrochemical properties
nuclear magnetic resonance
Polysilicon
Anions
Permittivity
Atoms
Oxidation-Reduction
polyanions
permittivity
anions

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

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title = "On the effect of ion pairing of Keggin type polyanions with quaternary ammonium cations on redox potentials in organic solvents",
abstract = "The electrochemical properties of Keggin type polyoxometalates Qn[XW12O40] (X = P, Si, B; Q = n-tetraoctylammonium and n-trioctylmethylammonium) in organic solvents were investigated in order to understand the interrelation between the redox potentials, solvents and ion pairing. A logarithmic correlation between the dielectric constant of the solvent (ϵ ranged from 4.8 to 46.6) and the reduction potential of the [PW12O4]3-/[PW12O4]4- couple was found. This reduction potential increased significantly when the surface charge of the polyoxometalate went from 3- to 5-. The investigation of the ion pairing properties by diffusion NMR revealed the presence of intimate ion pairs in less polar solvents (e.g. dichloromethane) and less compact ion pairs in more polar solvents (e.g. DMSO). Using a V atom within the polyoxometalate an NMR experiment showed that a n-trioctylmethyl ammonium cation bonded to the polyoxometalate anion more intimately than a n-tetraoctyl ammonium cation.",
author = "Bo Chen and Ronny Neumann",
year = "2016",
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language = "English",
volume = "18",
pages = "22487--22493",
journal = "Physical Chemistry Chemical Physics",
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TY - JOUR

T1 - On the effect of ion pairing of Keggin type polyanions with quaternary ammonium cations on redox potentials in organic solvents

AU - Chen, Bo

AU - Neumann, Ronny

PY - 2016

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N2 - The electrochemical properties of Keggin type polyoxometalates Qn[XW12O40] (X = P, Si, B; Q = n-tetraoctylammonium and n-trioctylmethylammonium) in organic solvents were investigated in order to understand the interrelation between the redox potentials, solvents and ion pairing. A logarithmic correlation between the dielectric constant of the solvent (ϵ ranged from 4.8 to 46.6) and the reduction potential of the [PW12O4]3-/[PW12O4]4- couple was found. This reduction potential increased significantly when the surface charge of the polyoxometalate went from 3- to 5-. The investigation of the ion pairing properties by diffusion NMR revealed the presence of intimate ion pairs in less polar solvents (e.g. dichloromethane) and less compact ion pairs in more polar solvents (e.g. DMSO). Using a V atom within the polyoxometalate an NMR experiment showed that a n-trioctylmethyl ammonium cation bonded to the polyoxometalate anion more intimately than a n-tetraoctyl ammonium cation.

AB - The electrochemical properties of Keggin type polyoxometalates Qn[XW12O40] (X = P, Si, B; Q = n-tetraoctylammonium and n-trioctylmethylammonium) in organic solvents were investigated in order to understand the interrelation between the redox potentials, solvents and ion pairing. A logarithmic correlation between the dielectric constant of the solvent (ϵ ranged from 4.8 to 46.6) and the reduction potential of the [PW12O4]3-/[PW12O4]4- couple was found. This reduction potential increased significantly when the surface charge of the polyoxometalate went from 3- to 5-. The investigation of the ion pairing properties by diffusion NMR revealed the presence of intimate ion pairs in less polar solvents (e.g. dichloromethane) and less compact ion pairs in more polar solvents (e.g. DMSO). Using a V atom within the polyoxometalate an NMR experiment showed that a n-trioctylmethyl ammonium cation bonded to the polyoxometalate anion more intimately than a n-tetraoctyl ammonium cation.

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