Porphyrin and Ligand Protons as Internal Labels for Determination of Ligand Orientation in ESEEMS of Low-Spin d5 Complexes in Glassy Media: ESEEM Studies of the Orientation of the g Tensor with Respect to the Planes of Axial Ligands and Porphyrin Nitrogens of Low-Spin Ferriheme Systems

摘要: The proton sum frequency peak(s), I(ν+), in the ESEEM spectra of low-spin ferriheme complexes provide single-crystal-like information concerning orientation g tensor samples frozen glassy media. In this work we have investigated two model heme complexes, [OEPFe(imidazole)2]+ and [OEPFe(4-(dimethylamino)pyridine)2]+ (OEP = octaethylporphyrinate). Both experimental intensities shifts from twice 1H Larmor observed signals were measured at various points across EPR spectrum compared to expected spectra, simulated using known crystal structure data, isotropic hyperfine coupling constants, strain. each case z magnetic axis direction was defined as perpendicular mean plane porphyrinate, it found that gzz is largest value both cases. in-plane directions could also be determined orientations gxx gyy differ, depending on orientati...