Issue 9, 2010

Chemical stability and application of a fluorophilic tetraalkylphosphonium salt in fluorous membrane anion-selective electrodes

Abstract

The highly fluorophilic phosphonium salt (Rf8(CH2)2)(Rf6(CH2)2)3P+I, 1, was used to provide cationic sites for anion-selective electrodes based on fluorous sensing membranes. The electrodes exhibited the theoretically expected “Nernstian” response slopes, and their selectivities for different anions were determined. For environmental analysis, the selective detection of perfluorooctanesulfonate and perfluorooctanoate is of particular interest. While previously reported electrodes based on a fluorophilic methyltriarylphosphonium salt suffered from OH interference to the extent that OH selectivities could not be determined, and general base catalysis caused decomposition of the phosphonium sites in the presence of weakly basic anions, electrode membranes based on 1 are much more robust. A loss of sensor response is only observed when the fluorous membranes doped with 1 are exposed to 0.1 M hydroxide solutions for 24 h. NMR and mass spectrometry show that the fluorophilic tetraalkylphosphonium cation of 1 decomposes under these extreme conditions to give two trialkylphosphine oxides and perfluoroalkylethanes. Interestingly, this decomposition is much slower than the base catalyzed exchange of the hydrogens in α position to the phosphonium center, which in the presence of D2O results in the quantitative formation of the octadeuterated tetraalkylphosphonium cation. While formation of a pentacoordinated transition state in the decomposition of 1 is likely, no pentavalent complexes of the phosphonium ion with OH could be observed by NMR spectroscopy.

Graphical abstract: Chemical stability and application of a fluorophilic tetraalkylphosphonium salt in fluorous membrane anion-selective electrodes

Article information

Article type
Paper
Submitted
21 Nov 2009
Accepted
07 Apr 2010
First published
05 May 2010

New J. Chem., 2010,34, 1867-1874

Chemical stability and application of a fluorophilic tetraalkylphosphonium salt in fluorous membrane anion-selective electrodes

L. D. Chen, D. Mandal, J. A. Gladysz and P. Bühlmann, New J. Chem., 2010, 34, 1867 DOI: 10.1039/B9NJ00696F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements