title: General synthesis of di-mu-oxo dimanganese complexes as functional models for the oxygen evolving complex of photosystem II.
abstract: A series of complexes with the formula [Mn(III/IV)2(mu-O)2(L)2(X)2]3+ have been prepared in situ from Mn(II)LCl2 precursors by a general preparative method (L = terpy, Cl-terpy, Br-terpy, Ph-terpy, tolyl-terpy, mesityl-terpy, t Bu3-terpy, EtO-terpy, py-phen, dpya, Me2N-terpy, or HO-terpy, and X = a labile ligand such as water, chloride, or sulfate). The parent complex, where L = terpy and X = water, is a functional model for the oxygen-evolving complex of photosystem II (Limburg, et al. J. Am. Chem. Soc. 2001, 123, 423-430). Crystals of Mn(II)(dpya)Cl2, Mn(II)(Ph-terpy)Cl2, Mn(II)(mesityl-terpy)Cl2, and an organic-soluble di-mu-oxo di-aqua dimanganese complex, [Mn(III/)(IV)2(mu-O)2(mesityl-terpy)2(OH2)2](NO3)3, were obtained and characterized by X-ray crystallography. Solutions of the in situ-formed di-mu-oxo dimanganese complexes were characterized by electrospray mass spectrometry, EPR spectroscopy, and UV-visible spectroscopy, and the rates of catalytic oxygen-evolving activity were assayed. The use of Mn(II)LCl2 precursors leads to higher product purity of the Mn dimers while achieving the 1:1 ligand to Mn stoichiometry appropriate for catalytic activity assay. These methods can be used to screen the catalytic activity of other di-mu-oxo dimanganese complexes generated by using a ligand library.
authors.affiliation: Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Chen
authors.forename: Ranitendranath
authors.initials: R
authors.lastname: Tagore
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Das
authors.forename: Christopher
authors.initials: C
authors.lastname: Incarvito
authors.forename: J W
authors.initials: JW
authors.lastname: Faller
authors.forename: Robert H
authors.initials: RH
authors.lastname: Crabtree
authors.forename: Gary W
authors.initials: GW
authors.lastname: Brudvig
mesh_terms: D018360:Crystallography, X-Ray; D008954:Models, Biological; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010100:Oxygen / Q000032:analysis*; D045332:Photosystem II Protein Complex / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D045332:Photosystem II Protein Complex; D010100:Oxygen