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Issue 25, 2015
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Challenging lanthanide relaxation theory: erbium and thulium complexes that show NMR relaxation rates faster than dysprosium and terbium analogues

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Abstract

Measurements of the proton NMR paramagnetic relaxation rates for several series of isostructural lanthanide(III) complexes have been performed in aqueous solution over the field range 1.0 to 16.5 Tesla. The field dependence has been modeled using Bloch–Redfield–Wangsness theory, allowing values for the electronic relaxation time, Tle and the magnetic susceptibility, μeff, to be estimated. Anomalous relaxation rate profiles were obtained, notably for erbium and thulium complexes of low symmetry 8-coordinate aza-phosphinate complexes. Such behaviour challenges accepted theory and can be interpreted in terms of changes in Tle values that are a function of the transient ligand field induced by solvent collision and vary considerably between Ln3+ ions, along with magnetic susceptibilities that deviate significantly from free-ion values.

Graphical abstract: Challenging lanthanide relaxation theory: erbium and thulium complexes that show NMR relaxation rates faster than dysprosium and terbium analogues

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The article was received on 16 Apr 2015, accepted on 02 Jun 2015 and first published on 02 Jun 2015


Article type: Paper
DOI: 10.1039/C5CP02210J
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Citation: Phys. Chem. Chem. Phys., 2015,17, 16507-16511

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    Challenging lanthanide relaxation theory: erbium and thulium complexes that show NMR relaxation rates faster than dysprosium and terbium analogues

    A. M. Funk, P. Harvey, K. N. A. Finney, M. A. Fox, A. M. Kenwright, N. J. Rogers, P. K. Senanayake and D. Parker, Phys. Chem. Chem. Phys., 2015, 17, 16507
    DOI: 10.1039/C5CP02210J

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