A low-spin CoII/Nitroxide complex for distance measurements at Q-band frequencies
Date
11/04/2022Grant ID
RPG-2018-397
BB/T017740/1
BB/R013780/1
Keywords
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Show full item recordAbstract
Pulse dipolar electron paramagnetic resonance spectroscopy (PDS) is continuously furthering the understanding of chemical and biological assemblies through distance measurements in the nanometer range. New paramagnets and pulse sequences can provide structural insights not accessible through other techniques. In the pursuit of alternative spin centers for PDS, we synthesized a low-spin CoII complex bearing a nitroxide (NO) moiety, where both the CoII and NO have an electron spin S of 1/2. We measured CoII-NO distances with the well-established double electron–electron resonance (DEER aka PELDOR) experiment, as well as with the five- and six-pulse relaxation-induced dipolar modulation enhancement (RIDME) spectroscopies at Q-band frequencies (34 GHz). We first identified challenges related to the stability of the complex in solution via DEER and X-ray crystallography and showed that even in cases where complex disproportionation is unavoidable, CoII-NO PDS measurements are feasible and give good signal-to-noise (SNR) ratios. Specifically, DEER and five-pulse RIDME exhibited an SNR of ~100, and while the six-pulse RIDME exhibited compromised SNR, it helped us minimize unwanted signals from the RIDME traces. Last, we demonstrated RIDME at a 10 μM sample concentration. Our results demonstrate paramagnetic CoII to be a feasible spin center in medium magnetic fields with opportunities for PDS studies involving CoII ions.
Citation
Giannoulis , A , Cordes , D B , Slawin , A M Z & Bode , B E 2022 , ' A low-spin Co II /Nitroxide complex for distance measurements at Q-band frequencies ' , Magnetochemistry , vol. 8 , no. 4 , 43 . https://doi.org/10.3390/magnetochemistry8040043
Publication
Magnetochemistry
Status
Peer reviewed
ISSN
2312-7481Type
Journal article
Rights
Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Description
Funding: AG was supported by the EPSRC funded Centre for Doctoral Training in ‘integrated magnetic resonance’, iMR-CDT (EP/J500045/1) the time the research was conducted. BEB is supported by the Leverhulme Trust (RPG-2018–397) and equipment funding from BBSRC (BB/R013780/1 and BB/T017740/1).Collections
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