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

Funk, Alexander M.; Harvey, Peter; Finney, Katie-Louise N. A.; Fox, Mark A.; Kenwright, Alan M.; Rogers, Nicola J.; Senanayake, P. Kanthi; Parker, David

Abstract

This journal is © the Owner Societies 2015. 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.

• Journal Article Type: Article
• Acceptance Date: Jun 2, 2015
• Online Publication Date: Jun 2, 2015
• Publication Date: Jun 2, 2015
• Deposit Date: Oct 23, 2019
• Journal: Physical Chemistry Chemical Physics
• Print ISSN: 1463-9076
• Electronic ISSN: 1463-9084
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 17
• Issue: 25
• Pages: 16507-16511
• DOI: https://doi.org/10.1039/c5cp02210j
• Public URL: https://nottingham-repository.worktribe.com/output/2829365
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : The PCCP Owner Societies have an exclusive publication licence for this journal; OPEN ACCESS: The accepted version of this article will be made freely available after a 12 month embargo period; : Single-blind; : Received 16 April 2015; Accepted 2 June 2015; Accepted Manuscript published 2 June 2015; Advance Article published 8 June 2015; Version of Record published 17 June 2015