EXAFS of Poly [μ-hexakis(2-methylimidazolato-N,N')triiron( II)]: Implications for Metalloprotein Studies

Abstract

EXAFS data at the Fe K-edge of the coordination compound poly[mu-hexakis(2-methylimidazolato-N,N3triiron(II)] are presented. Single-scattering analysis of the EXAFS gives good agreement with the crystallographic data for the first two shells of atoms around the iron, but beyond that, multiple-scattering simulations are needed. The EXAFS data do not unambiguously indicate the presence of the methyl substituent, and upon refinement of the multiple-scattering simulation, artificially large spreads between atoms occurring at similar distances are observed. These findings imply that, in the analysis of metalloprotein EXAFS data, it is not possible to probe the difference between pros and tefe coordination of imidazoles, while the potential to obtain information on possible tilting of the imidazole ring relative to the metal-N1 bond is weak.