Electronic structure analysis of iron(III)-porphyrin complexes by X-ray absorption spectra at the C, N and Fe K-edges

Anal Sci. 2005 Mar;21(3):309-14. doi: 10.2116/analsci.21.309.

Abstract

X-ray absorption near edge structure (XANES) measurements at the C, N, and Fe K absorption edges were performed for iron(III)-tetraphenylporphyrin (FeTPP), iron(III)-tetrakis(p-carboxyphenyl)porphyrin (FeTCPP), and iron(III)-tetrakis(p-sulfonatophenyl)porphyrin (FeTSPP). The spectral shapes differ in the Fe K XANES, but not in C and N K XANES among FeTPP, FeTCPP, and FeTSPP. Crosschecks of XANES data for C, N, and Fe K absorption edges in combination with discrete variational (DV)-Xalpha molecular orbital (MO) calculations indicate that each p-electron-withdrawing group on four meso-phenyl substitutes in an Fe(III)-porphyrin complex brings about a unique electron state through the complex because of the electron-withdrawal strength, itself. Consequently, they affect the positive charge of the center Fe(III) ion.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Absorptiometry, Photon / methods*
  • Carbon / chemistry*
  • Electrons
  • Iron / chemistry*
  • Metalloporphyrins / chemistry*
  • Molecular Structure
  • Nitrogen / chemistry*

Substances

  • Metalloporphyrins
  • iron(III)-tetrakis(p-carboxyphenyl)porphyrin
  • iron(III)-tetrakis(p-sulfonatophenyl)porphyrin
  • iron(III)-tetraphenylporphyrin
  • Carbon
  • Iron
  • Nitrogen