title: Characterization of synthetic oxomanganese complexes and the inorganic core of the O2-evolving complex in photosystem II: evaluation of the DFT/B3LYP level of theory.
abstract: The capabilities and limitations of the Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional are investigated as applied to studies of mixed-valent multinuclear oxomanganese complexes. Benchmark calculations involve the analysis of structural, electronic and magnetic properties of di-, tri- and tetra-nuclear Mn complexes, previously characterized both chemically and spectroscopically, including the di-mu-oxo bridged dimers [Mn(III)Mn(IV)(mu-O)(2)(H(2)O)(2)(terpy)(2)](3+) (terpy=2,2':6,2''-terpyridine) and [Mn(III)Mn(IV)(mu-O)(2)(phen)(4)](3+) (phen=1,10-phenanthroline), the Mn trimer [Mn(3)O(4)(bpy)(4)(H(2)O)(2)](4+) (bpy=2,2'-bipyridine), and the tetramer [Mn(4)O(4)L(6)](+) with L=Ph(2)PO(2)(-). Furthermore, the density functional theory (DFT) B3LYP level is applied to analyze the hydrated Mn(3)O(4)CaMn cluster completely ligated by water, OH(-), Cl(-), carboxylate and imidazole ligands, analogous to the '3+1 Mn tetramer' of the oxygen-evolving complex of photosystem II. It is found that DFT/B3LYP predicts structural and electronic properties of oxomanganese complexes in pre-selected spin-electronic states in very good agreement with X-ray and magnetic experimental data, even when applied in conjunction with rather modest basis sets. However, it is conjectured that the energetics of low-lying spin-states is beyond the capabilities of the DFT/B3LYP level, constituting a limitation to mechanistic studies of multinuclear oxomanganese complexes where until now the performance of DFT/B3LYP has raised little concern.
authors.affiliation: Department of Chemistry, Yale University, 225 Prospect Street, P.O. Box 208107, New Haven, CT 06520-8107, USA.
authors.forename: Eduardo M
authors.initials: EM
authors.lastname: Sproviero
authors.forename: Jose A
authors.initials: JA
authors.lastname: Gascon
authors.forename: James P
authors.initials: JP
authors.lastname: McEvoy
authors.forename: Gary W
authors.initials: GW
authors.lastname: Brudvig
authors.forename: Victor S
authors.initials: VS
authors.lastname: Batista
mesh_terms: D032701:Biomimetics; D004578:Electron Spin Resonance Spectroscopy; D005069:Evaluation Studies as Topic; D006878:Hydroxides / Q000737:chemistry; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D006878:Hydroxides; D008024:Ligands; D009942:Organometallic Compounds; D045332:Photosystem II Protein Complex; D014867:Water; D008345:Manganese; C031356:hydroxide ion; D010100:Oxygen