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The protonation state and binding mode in a metal coordination complex from the charge measured in solution by electrophoretic NMR
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.ORCID iD: 0000-0002-7552-1076
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.ORCID iD: 0000-0002-0231-3970
2013 (English)In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 5, no 7, 1648-1651 p.Article in journal (Refereed) Published
Abstract [en]

We measured with high accuracy the effective charge of a uranium (VI)-AMP complex by electrophoretic NMR (eNMR). Using the same method, the degree of counterion association is also assessed which leads to a quantitative determination of the nominal charge which then provides the degree of ligand deprotonation in the complex. This demonstrates a new application of eNMR for resolving structural details of supramolecular complexes.

Place, publisher, year, edition, pages
2013. Vol. 5, no 7, 1648-1651 p.
Keyword [en]
Multinuclear Nmr, Stability-Constants, Uranyl Acetate, Ions, Polyelectrolytes, Nucleotides, Uranium, Cells
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-120562DOI: 10.1039/c3ay00023kISI: 000316118500002ScopusID: 2-s2.0-84879538166OAI: diva2:615807
Swedish Research Council

QC 20130412

Available from: 2013-04-12 Created: 2013-04-11 Last updated: 2015-02-12Bibliographically approved
In thesis
1. Characterizing ions in solution by NMR methods
Open this publication in new window or tab >>Characterizing ions in solution by NMR methods
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

NMR experiments performed under the effect of electric fields, either continuous or pulsed, can provide quantitative parameters related to ion association and ion transport in solution.  Electrophoretic NMR (eNMR) is based on a diffusion pulse-sequence with electric fields applied in the form of pulses. Magnetic field gradients enable the measurement of the electrophoretic mobility of charged species, a parameter that can be related to ionic association.

The effective charge of the tetramethylammonium cation ion in water, dimethylsulphoxide (DMSO), acetonitrile, methanol and ethanol was estimated by eNMR and diffusion measurements and compared to the value predicted by the Debye-Hückel-Onsager limiting law. The difference between the predicted and measured effective charge was attributed to ion pairing which was found to be especially significant in ethanol.

The association of a large set of cations to polyethylene oxide (PEO) in methanol, through the ion-dipole interaction, was quantified by eNMR. The trends found were in good agreement with the scarce data from other methods. Significant association was found for cations that have a surface charge density below a critical value. For short PEO chains, the charge per monomer was found to be significantly higher than for longer PEO chains when binding to the same cations. This was attributed to the high entropy cost required to rearrange a long chain in order to optimize the ion-dipole interactions with the cations. Moreover, it was suggested that short PEO chains may exhibit distinct binding modes in the presence of different cations, as supported by diffusion measurements, relaxation measurements and chemical shift data.

The protonation state of a uranium (VI)-adenosine monophosphate (AMP) complex in aqueous solution was measured by eNMR in the alkaline pH range. The question whether or not specific oxygens in the ligand were protonated was resolved by considering the possible association of other species present in the solution to the complex.

The methodology of eNMR was developed through the introduction of a new pulse-sequence which suppresses artifactual flow effects in highly conductive samples.

In another experimental setup, using NMR imaging, a constant current was applied to a lithium ion (Li ion) battery model. Here, 7Li spin-echo imaging was used to probe the spin density in the electrolyte and thus visualize the development of Li+ concentration gradients. The Li+ transport number and salt diffusivity were obtained within an electrochemical transport model. The parameters obtained were in good agreement with data for similar electrolytes. The use of an alternative imaging method based on CTI (Constant Time Imaging) was explored and implemented.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xii, 58 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:29
electrophoretic NMR, diffusion NMR, NMR imaging, ion pairing, ion association, polyethylene oxide, metal-ion complex, Li ion batteries, electrolyte characterization
National Category
Natural Sciences
Research subject
urn:nbn:se:kth:diva-149552 (URN)978-91-7595-208-6 (ISBN)
Public defence
2014-09-12, F3, Lindstedtsvägen 26, KTH, Stockholm, 14:00 (English)
Swedish Research CouncilKnut and Alice Wallenberg Foundation

QC 20140825

Available from: 2014-08-25 Created: 2014-08-22 Last updated: 2014-08-25Bibliographically approved

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