Simulating Frequency-Domain Electron Paramagnetic Resonance: Bridging the Gap between Experiment and Magnetic Parameters for High-Spin Transition-Metal Ion Complexes

Joscha Nehrkorn; Joshua Telser; Karsten Holldack; Stefan Stoll; Alexander Schnegg

doi:10.1021/acs.jpcb.5b04156

Simulating Frequency-Domain Electron Paramagnetic Resonance: Bridging the Gap between Experiment and Magnetic Parameters for High-Spin Transition-Metal Ion Complexes

J Phys Chem B. 2015 Oct 29;119(43):13816-24. doi: 10.1021/acs.jpcb.5b04156. Epub 2015 Jul 24.

Authors

Joscha Nehrkorn¹, Joshua Telser², Karsten Holldack³, Stefan Stoll⁴, Alexander Schnegg¹

Affiliations

¹ Berlin Joint EPR Lab, Institute for Nanospectroscopy, Helmholtz-Zentrum Berlin für Materialien und Energie , Kekuléstraße 5, 12489 Berlin, Germany.
² Department of Biological, Chemical and Physical Sciences, Roosevelt University , 430 South Michigan Avenue, Chicago, Illinois 60605, United States.
³ Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie , Albert-Einstein-Straße 15, 12489 Berlin, Germany.
⁴ Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195, United States.

PMID: 26154490
DOI: 10.1021/acs.jpcb.5b04156

Abstract

We present a comparison of experimental and simulated frequency- and field-domain electron paramagnetic resonance (EPR) spectra of integer and half-integer high-spin transition-metal ion complexes. For the simulation of EPR spectra a new tool within the EPR simulation software EasySpin is introduced, which allows for field- and frequency-domain EPR simulations with the same theoretical model and the same set of spin Hamiltonian parameters. The utility of this approach is demonstrated on the integer-spin complexes NiBr2(PPh3)2 and [Tp2Mn]SbF6 (both S = 1) and the half-integer-spin Fe(III) porphyrins, hemin (Fe(PPIX)Cl) and Fe(TPP)Cl (both S = 5/2). We demonstrate that the combination of field- and frequency-domain EPR techniques allows the determination of spin Hamiltonian parameters, in particular large zero-field splittings, with high accuracy.