Abstract
Understanding how the ligand shell controls low-frequency electron paramagnetic resonance (EPR) spectroscopic properties of metal ions is essential if they are to be used in EPR-based bioimaging schemes. In this work, we probe how specific variations in the ligand structure impact L-band (ca. 1.3 GHz) EPR spectroscopic linewidths in the trichloride salts of five Cr(iii) complexes: [Cr(RR-dphen)3]3+(RR-dphen = (1R,2R)-(+)-diphenylethylenediamine,1), [Cr(en)3]3+(en = ethylenediamine,2), [Cr(me-en)3]3+(me-en = 1,2-diaminopropane,3), [Cr(tn)3]3+(tn = 1,3-diaminopropane,4) [Cr(trans-chxn)3]3+(trans-chxn =trans-(±)-1,2-diaminocyclohexane,5). Spectral broadening varies in a nonintuitive manner across the series, showing the sharpest peaks for1and broadest for5. Molecular dynamics simulations provide evidence that the broadening is correlated to rigidity in the inner coordination sphere and reflected in ligand-dependent distribution of Cr-N bond distances that can be found in frozen solution.
| Original language | English |
|---|---|
| Pages (from-to) | 5342-5350 |
| Number of pages | 9 |
| Journal | Dalton Transactions |
| Volume | 50 |
| Issue number | 15 |
| DOIs | |
| State | Published - Apr 21 2021 |
| Externally published | Yes |
Funding
We thank Prof. M. Reynolds, C. Allison, and M. Roach for use of their mass spectrometer. This research was performed with the support of Colorado State University (CSU) and the NIH (R21-EB027293) (A. J. C., J. M. Z.). Part of the work described in this publication was performed at Pacific Northwest National Laboratory (PNNL), which is operated by Battelle for the United States Department of Energy (DOE) under Contract DE-AC05-76RL01830. M.-T. N., J. Z. and V.-A. G. acknowledge support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231 and PNNL’s Research Computing.