General synthesis of Di-μ-oxo dimanganese complexes as functional models for the oxygen evolving complex of photosystem II

Hongyu Chen, Ranitendranath Tagore, Siddhartha Das, Christopher Incarvito, J. W. Faller, Robert H. Crabtree, Gary W. Brudvig

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Abstract

A series of complexes with the formula [MnIII/IV 2(μ-O)2(L)2(X)2]3+ have been prepared in situ from MnIILCl2 precursors by a general preparative method (L = terpy, Cl-terpy, Br-terpy, Ph-terpy, tolyl-terpy, mesityl-terpy, tBu3-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 MnII(dpya) Cl2, MnII(Ph-terpy)-Cl2, Mn II(mesityl-terpy)Cl2, and an organic-soluble di-μ-oxo di-aqua dimanganese complex, [MnIII/IV2(μ-O) 2(mesityl-terpy)2(OH2)2](NO 3)3, were obtained and characterized by X-ray crystallography. Solutions of the in situ-formed di-μ-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 MnIILCl2 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-μ-oxo dimanganese complexes generated by using a ligand library.

Original languageEnglish
Pages (from-to)7661-7670
Number of pages10
JournalInorganic Chemistry
Volume44
Issue number21
DOIs
Publication statusPublished - Oct 17 2005

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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