Issue 45, 2020

EXAFS investigations of temperature-dependent structure in cobalt-59 molecular NMR thermometers

Abstract

Cobalt-59 nuclei are known for extremely thermally sensitive chemical shifts (δ), which in the long term could yield novel magnetic resonance thermometers for bioimaging applications. In this manuscript, we apply extended X-ray absorption fine structure (EXAFS) spectroscopy for the first time to probe the exact variations in physical structure that produce the exceptional thermal sensitivity of the 59Co NMR chemical shift. We apply this spectroscopic technique to five Co(III) complexes: [Co(NH3)6]Cl3 (1), [Co(en)3]Cl3 (2) (en = ethylenediamine), [Co(tn)3]Cl3 (3) (tn = trimethylenediamine), [Co(tame)2]Cl3 (4) (tame = 1,1,1-tris(aminomethyl)ethane), and [Co(diNOsar)]Cl3 (5) (diNOsar = dinitrosarcophagine). The solution-phase EXAFS data reveal increasing Co–N bond distances for these aqueous complexes over a ∼50 °C temperature window, expanding by Δr(Co–N) = 0.0256(6) Å, 0.0020(5) Å, 0.0084(5) Å, 0.0006(5) Å, and 0.0075(6) Å for 1–5, respectively. Computational analyses of the structural changes reveal that increased connectivity between the donor atoms encourages complex structural variations. These results imply that rich temperature-dependent structural variations define 59Co NMR thermometry in macrocyclic complexes.

Graphical abstract: EXAFS investigations of temperature-dependent structure in cobalt-59 molecular NMR thermometers

Supplementary files

Article information

Article type
Paper
Submitted
16 abr 2020
Accepted
24 mai 2020
First published
26 mai 2020

Dalton Trans., 2020,49, 16380-16385

Author version available

EXAFS investigations of temperature-dependent structure in cobalt-59 molecular NMR thermometers

T. M. Ozvat, G. E. Sterbinsky, A. J. Campanella, A. K. Rappé and J. M. Zadrozny, Dalton Trans., 2020, 49, 16380 DOI: 10.1039/D0DT01391A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements