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Synthesis and characterisation of low valent Mn-complexes as models for Mn-catalases
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
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2010 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 45, 11035-11044 p.Article in journal (Refereed) Published
Abstract [en]

In this work we report the synthesis of two novel manganese complexes, [L1(3)Mn(6)(II)](ClO4)(6) (1 center dot(ClO4)(6)) and [L2Mn(2)(II)(mu-OAc)(mu-Cl)](ClO4)(2) (2 center dot(ClO4)(2)), where L1(2-) is the 2,2'-(1,3-phenylenebis(methylene))bis-((2-(bis(pyridin-2-ylmethyl)amino)ethyl)azanediyl)diacetic acid anion and L2 is N1,N1'-(1,3-phenylenebis(methylene))bis(N2,N2'-bis(pyridin-2-ylmethyl)ethane-1,2-diamine). The ligands Na(2)L1 and L2 are built on the same backbone, L2 only contains nitrogen donors, while two carboxylate arms have been introduced in Na(2)L1. The two complexes have been characterized by single-crystal X-ray diffraction, magnetic susceptibility, EPR spectroscopy, and electrochemistry. X-Ray crystallography revealed that 1 is a manganese(II) hexamer and 2 is a manganese(II) dimer featuring an unprecedented mono-mu-acetato, mono-mu-chlorido bridging motif. The ability of the complexes to catalyse H2O2 disproportionation, thereby acting as models for manganese catalases, has been investigated and compared to the activity of two other related manganese complexes. The introduction of carboxylate donors in the ligands, leading to increased denticity, resulted in a drop in H2O2 disproportionation activity.

Place, publisher, year, edition, pages
2010. Vol. 39, no 45, 11035-11044 p.
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-108525DOI: 10.1039/c0dt00165aISI: 000284066100028OAI: oai:DiVA.org:uu-108525DiVA: diva2:236182
Available from: 2009-09-21 Created: 2009-09-21 Last updated: 2016-04-22
In thesis
1. Mimicking Nature – Synthesis and Characterisation of Manganese Complexes of Relevance to Artificial Photosynthesis
Open this publication in new window or tab >>Mimicking Nature – Synthesis and Characterisation of Manganese Complexes of Relevance to Artificial Photosynthesis
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of efficient catalyst for water oxidation is of paramount importance to artificial photosynthesis, but before this can be achieved a deeper understanding of this reaction is essential. In nature this reaction occurs in a tetranuclear Mn-cluster which serves as the work-horse of oxygenic photosynthesis. This thesis summarises my efforts at developing molecular systems capable of mimicking this complex employing a biomimetic approach.

Three different approaches towards this goal are described here-in. The first section describes a screening study, in which a number of manganese complexes were tested to see whether or not they were capable of catalysing the formation of dioxygen when treated with different oxidants (Papers I). For those reactions in which dioxygen formation was observed the reactions were repeated in labelled water and the incorporation of labelled O-atoms was studied by mass spectrometry. This allowed us to determine to what extent water was the source of the evolved dioxygen (Papers II-III).

In Chapter three a reported catalyst and a derivative thereof is studied in depth. The influence of changes to the ligand on the oxygen–oxygen bond forming reaction could unfortunately not be reliably addressed, because of the instability of the complexes under “catalytic” conditions. Nevertheless, the study allowed us to revise the “carboxylate shift”-mechanism suggested in the literature (Papers IV-V).

Chapter four describes the continuation of my work on ligands featuring the carboxylate ligand motif first introduced in Chapter three. In this study ligands containing multiple binding pockets were designed and synthesised (Paper VI).

A better understanding of the mechanism in the natural water oxidising enzyme will facilitate the design of biomimetic complexes, this is discussed in Chapter five. In this work model complexes (Paper VII) are used to study the mechanism by which natures own water oxidising catalyst performs this reaction.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 101 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 674
Keyword
Manganese, biomimetic, artificial photosynthesis, water splitting, homogeneous catalysis
National Category
Other Basic Medicine
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-108526 (URN)978-91-554-7614-4 (ISBN)
Public defence
2009-11-06, Polhemsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
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Supervisors
Available from: 2009-10-15 Created: 2009-09-21 Last updated: 2009-10-15Bibliographically approved

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Berggren, GustavHuang, PingStyring, StenbjörnThapper, Anders

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