Nuclear resonant forward scattering using synchrotron radiation applied to study the low-spin ferriheme complex [TPPFe(NH2PzH)2]Cl

Abstract

We have characterised the low-spin ferriheme complex bis(3-aminopyrazole)tetraphenyl-porphyrinatoiron(III) chloride ([TPPFe(NH2PzH)2]Cl) by nuclear resonant forward scattering (NFS) using synchrotron radiation at 4.2K in fields up to 6T. The analysis of the field dependant NFS spectra obtained with the g-tensor determined by previous pulsed EPR measurements [1] (g=(1.87, 2.28, 2.39)) yields the hyperfine parameters η = 0.0; β = 90°; y = 90°; ΔEQ = −2.56 mm/s and A/μngn = (−46.9, 9.5, 17.6) T. This investigation shows that NFS provides higher accuracy in determining hyperfine parameters than conventional Mossbauer spectroscopy, if the delay time is long enough and the effective thickness is relatively high (in the present case t ≈ 150 ns and teff ≈ 10).