Raman spectra and normal coordinate analyses of low-frequency vibrations of oxo-bridged manganese complexes

Agnes Cua, John S. Vrettos, Julio C. De Paula, Gary W. Brudvig, David F. Bocian

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The active sites of certain metalloenzymes involved in oxygen metabolism, such as manganese catalase and the oxygen-evolving complex of photosystem II, contain μ-oxo-bridged Mn clusters with ligands that include H2O and μ1,3-carboxylato bridges provided by protein side chains. In order to understand better the vibrational spectra of such clusters, the low-frequency resonance Raman spectra of a series of structurally characterized Mn-oxo model complexes were examined. The series includes complexes of the type [Mn2(O) (OAc)2(bpy)2(L)2] and [Mn2(O)2(OAc)(bpy)2(L)2], where bpy = 2,2′-bipyridine, OAc=acetate and L=H2O or Cl-. Complexes containing the isotopomers OAc-d3 and D2O, as well as those containing both isotopomers, were also examined. Normal coordinate analyses (NCA) were performed on the various complexes using the GF matrix method. Selected vibrational modes in the 200-600 cm-1 region were assigned based on the spectra and NCA, which identify vibrational modes arising from the metal-ligand bonds. These results will be useful in interpreting the vibrational spectra obtained from metalloproteins containing Mn-oxo complexes in their active sites.

Original languageEnglish
Pages (from-to)439-451
Number of pages13
JournalJournal of Biological Inorganic Chemistry
Volume8
Issue number4
Publication statusPublished - Apr 1 2003

Keywords

  • Low-frequency vibrations
  • Manganese
  • Normal coordinate analysis
  • Photosystem II
  • Raman spectroscopy

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

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