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.


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.