Reversible Enzymatic Switching of the Oxidation State of a Eu <sup>III/II</sup> Complex Controls Relaxivity
We show that europium trisbipyridyl cryptate exhibits an electrochemically reversible Eu<sup>III/II</sup> redox couple at -360 mV vs the standard hydrogen electrode (SHE) and is susceptible to reduction or oxidation by a range of redox enzymes or biological small molecule redox agents. Modulation of the europium oxidation state can be used to achieve dramatic changes in the <i>T</i><sub>1</sub> relaxation time of bulk water in solutions containing these complexes: in the reduced form, the complex exhibits high relaxivity (3.08 mM<sup>-1</sup> s<sup>-1</sup> at 499.9 MHz) comparable with that of commercial MRI contrast media, while the oxidized form has negligible relaxivity, illustrating the scope for application in imaging reducing environments in biological systems.
Authors
- Kylie A. Vincent (ORCID: https://orcid.org/0000-0001-6444-9382)
- Ester M. Hammond (ORCID: https://orcid.org/0000-0002-2335-3146)
- Saul M. Cooper (ORCID: https://orcid.org/0000-0003-0043-0249)
- Stephen Faulkner (ORCID: https://orcid.org/0000-0003-1878-5857)
- Adam C. Sedgwick (ORCID: https://orcid.org/0000-0002-3132-2913)
- Sophie A. Twigger (ORCID: https://orcid.org/0000-0002-9066-7700)
- Adam C. Berger (ORCID: https://orcid.org/0000-0002-8224-6797)
- Euan T. Sarson (ORCID: https://orcid.org/0009-0008-5023-3570)
Institutions
- University of Oxford (GB)
- Building Research Institute (JP)
Publication Details
- Journal
- Journal of the American Chemical Society
- Published
- 2025-10-16
- DOI
- https://doi.org/10.1021/jacs.5c13447
- Primary Topic
- Lanthanide and Transition Metal Complexes
- Type
- article
- Field-Weighted Citation Impact
- 0.00