title: Ab Initio modeling of the effect of oxidation coupled with HnO deprotonation on carboxylate ligands in Mn/Ca clusters.
abstract: Oxidation of some manganese complexes containing both carboxylate and water/hydroxo ligands does not result in changes to the carboxylate stretching frequencies. The water oxidizing complex of photosystem II is one motivating example. On the basis of electronic structure theory calculations, we here suggest that the deprotonation of water or hydroxo ligands minimizes changes in the vibrational frequencies of coligating carboxylates, rendering the carboxylate modes "invisible" in FTIR difference spectroscopy. This deprotonation of water/hydroxo ligands was also found to balance the redox potentials of the Mn(II)/Mn(III) and Mn(III)/Mn(IV) couples, allowing the possibility for successive manganese oxidations at a relatively constant redox potential.
authors.affiliation: Research School of Chemistry, Australian National University , ACT 0200, Australia.
authors.forename: Wooi Yee
authors.initials: WY
authors.lastname: Chuah
authors.forename: Rob
authors.initials: R
authors.lastname: Stranger
authors.forename: Ron J
authors.initials: RJ
authors.lastname: Pace
authors.forename: Elmars
authors.initials: E
authors.lastname: Krausz
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Frankcombe
mesh_terms: D002118:Calcium / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism; D011522:Protons; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry
chemical_list: D002264:Carboxylic Acids; D008024:Ligands; D045332:Photosystem II Protein Complex; D011522:Protons; D014867:Water; D008345:Manganese; D002118:Calcium