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Tuning the electronic properties of Fe2(μ-arenedithiolate) (CO)6-n(PMe3)n (n = 0, 2) complexes related to the [FeFe] hydrogenase active site
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
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2008 (English)In: Comptes rendus. Chimie, ISSN 1631-0748, Vol. 11, no 8, 875-889 p.Article in journal (Refereed) Published
Abstract [en]

Complexes [Fe-2(mu-S2Ar)(CO)(6)] (S2Ar) = benzene-1,2-dithiolate (1a) toluene-3,4-dithiolate (2a), 3,6-dichloro-1,2-benzenedithiolate (3a), quinoxaline-2,3-dithiolate (7a) have been prepared to investigate the electronic effect that different bridging arenedithiolate ligands have on the appended Fe-2(CO)(6) sites. Dinuclear complexes [Fe-2(mu-S2Ar)(CO)(4)(PMe3)(2)] (1-3,7)b and mononuclear complexes [Fe(S2Ar)(CO)(2)(PMe3)(2)] (1-3,7)c were synthesized from their parent hexacarbonyl complexes (1-3,7)a. IR spectroscopic, crystallographic and electrochemical analyses show that an increase of the electron-withdrawing character (where quinoxaline-2,3-dithiolate > ; 3,6-dichloro-1,2-benzenedithiolate > , 1,2-benzenedithiolate > ; toluene-3,4-dithiolate) of the bridging ligand leads to a decreased electron density at the iron centers, which yield a milder reduction potential and higher eCO stretching frequencies. This effect is coherent for all of the investigated complexes. Electrocatalytic proton reduction by complex 3a (with trifluoromethanesulfonic acid) was evidenced by cyclic voltammetry. As a result of the milder reduction potential of 3a itself, proton reduction that is promoted by 3a proceeds at a potential that is milder than that for the 1a-catalyzed process.

Place, publisher, year, edition, pages
2008. Vol. 11, no 8, 875-889 p.
Keyword [en]
bioinorganic chemistry, electrochemistry, IR spectroscopy, hydrogen production
National Category
Chemical Sciences
URN: urn:nbn:se:uu:diva-98035DOI: 10.1016/j.crci.2008.04.001ISI: 000258393100009OAI: oai:DiVA.org:uu-98035DiVA: diva2:173198
Available from: 2009-02-12 Created: 2009-02-12 Last updated: 2015-06-01Bibliographically approved
In thesis
1. Synthetic [FeFe] Hydrogenase Active Site Model Complexes
Open this publication in new window or tab >>Synthetic [FeFe] Hydrogenase Active Site Model Complexes
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

[FeFe]-Hydrogenases (H2ases) are metalloenzymes that can catalyze the reversible reduction of protons to molecular hydrogen as part of the metabolism of certain cyanobacteria and green algae. Due to the low availability of the enzyme, synthetic complexes that mimic the natural active site in structure, function and activity are highly sought after. In this thesis, a number of [FeFe]-H2ases active site model complexes were synthesized to answer open questions of the active site and to develop unprecedented bio-inspired proton reduction catalysts.

The first part describes the synthesis and the protonation properties of a [Fe2(μ-adt)(CO)4(PMe3)2] (adt = azadithiolate) complex which contains two basic sites that are similar to those found in the enzyme active site. Unusual kinetic factors give rise to four discrete protonation states. The twofold protonated state is the first model complex that simultaneously carries a proton at the azadithiolate nitrogen and a bridging hydride at the Fe-Fe bond.

In the second part, a model complex with an unprecedented amine ligand was synthesized and studied. In analogy to the enzyme active site, the labile amine ligand is expelled after electrochemical reduction.

The third part describes a series of model complexes with electronically different aromatic dithiolate ligands. It is demonstrated in one case that the tuning of the ligand by electron-withdrawing substituents results in proton reduction catalysis at an overpotential that is lower than that required by the non-substituted parent compound.

The design and the synthetic work towards a new ruthenium-diiron dyad for light-driven hydrogen production are presented in the fourth part.

In the final part, differently isotope-labelled mixed valent Fe(I)-Fe(II) model complexes were synthesized, in particular the unprecedented 15N labelled analogue, with the aim to provide EPR-spectroscopic references that will allow the elucidation of the nature of the central atom in the dithiolate bridge of the [FeFe] hydrogenase active site.

Place, publisher, year, edition, pages
Uppsala: Universitetsbiblioteket, 2009. 88 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 599
hydrogenase mimic, proton reduction, bioinorganic chemistry, diiron hexacarbonyl complexes, artifical photosynthesis, hydrogen
National Category
Organic Chemistry
urn:nbn:se:uu:diva-9548 (URN)978-91-554-7404-1 (ISBN)
Public defence
2009-03-06, Å4001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Available from: 2009-02-12 Created: 2009-02-12 Last updated: 2010-03-04Bibliographically approved

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Lomoth, Reiner
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