title: Two tetranuclear Mn-complexes as biomimetic models of the oxygen evolving complex in Photosystem II. A synthesis, characterisation and reactivity study.
abstract: In this work we report the preparation of two metallamacrocyclic tetranuclear manganese(II) complexes, [L1(4)Mn4](ClO4)4 and [L2(4)Mn4](ClO4)4 where L1 and L2 are the anions of the heptadentate ligands 2-((2-(bis(pyridin-2-ylmethyl)amino)ethyl)(methyl)amino)acetic acid and 2-(benzyl(2-(bis(pyridin-2-ylmethyl)amino)ethyl)amino)acetic acid), respectively. The complexes have been fully characterized by ESI-MS, elemental analysis, single-crystal X-ray diffraction, magnetic susceptibility, and EPR spectroscopy. Electrochemical reactions as well as reactions with different chemical redox reagents have been performed and a reversible two electron oxidation per manganese ion has been identified. The reaction of [L1(4)Mn4](ClO4)4 with oxone or cerium(IV) results in the evolution of oxygen which makes this system interesting for future studies in the search for a functional mimic of the oxygen evolving complex in Photosystem II.
authors.affiliation: Dept. of Photochemistry and Molecular Science, P.O. Box 523, S-75120, Uppsala, Sweden.
authors.forename: Gustav
authors.initials: G
authors.lastname: Berggren
authors.forename: Anders
authors.initials: A
authors.lastname: Thapper
authors.forename: Ping
authors.initials: P
authors.lastname: Huang
authors.forename: Philipp
authors.initials: P
authors.lastname: Kurz
authors.forename: Lars
authors.initials: L
authors.lastname: Eriksson
authors.forename: Stenbjörn
authors.initials: S
authors.lastname: Styring
authors.forename: Magnus F
authors.initials: MF
authors.lastname: Anderlund
mesh_terms: D032701:Biomimetics; D002384:Catalysis; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D008024:Ligands; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D008954:Models, Biological; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry*
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D045332:Photosystem II Protein Complex; D008345:Manganese; D010100:Oxygen