TABLE 2.

Manganese and iron K-edge energies and relative amounts of M(II) and (III) ions

K-edge energies reflect the 50% level of XANES spectra (Figs. 2 and 5), the error was ∼0.15 eV. Oxidation state references are octahedral metal species, namely Mn(II) O₆ in hexaquo-Mn(II) in a 3 mm solution of MnCl₂, Mn(III)O₄N₂ in a powder sample of a synthetic Mn₂ complex (115), Fe(II)N₄O₂ in the non-heme iron site of bacterial photosynthetic reaction center protein (98), and Fe(III)N₅O in the heme of oxidized bovine hemoglobin in 15 mm solution. Indices xi specify the mean x-ray exposure in min. Metal (M) site amounts were calculated using linear relations between K-edge energies and oxidation states (Figs. 2B and 4; for CtR2_MnFe^ox neglecting a minor Mn(IV) contribution). CtR2_MnFe^x-ray denotes a state reached after ∼130 min of XPR.