Spectroscopic and structural investigations of the ferrous and ferric high-spin state of a “picket—fence” porphyrinato acetato iron complex. A refined model for the P460 center of hydroxylamine oxidoreductase

Abstract

Mössbauer investigations were performed in the ferrous and ferric form of the ‘picket-fence’ porphyrinato acetato iron complex |Fe(CH₃CO₂) (TP_pivP)|^1−,0 at temperatures varying from 1.5–200K and in fields of 0–6.2T. The ferrous complex has an unusually large quadrupole splitting, ΔE_Q=+4.25mms⁻¹. The quadrupole splitting in the ferric species, ΔE_Q=+1.1mms⁻¹, is as normally found in ferric high-spin iron porphyrins. Spin-Hamiltonian analysis of the magnetic spectra yields zero-field parameters D=−0.9mms⁻¹, E/D=0.33 and magnetic hyperfine parameters A_x,y=−17T, A_z=−13.3T in the ferrous high-spin (S=2) complex, and D=7.5cm⁻¹, E/D≈0 and A_x,y,z=20T in the ferric high-spin (S=5/2) species.