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Ruthenium(II) Polypyridyl Complexes in Supramolecular Systems relevant to Artificial Photosynthesis
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes the synthesis and properties of ruthenium complexes relevant to artificial photosynthesis. The work includes preparation of RuIIpolypyridine complexes as well as multi component systems where RuII(bpy)3 or RuII(tpy)2 type complexes are used as photosesnsitizers.

In the first part, the synthesis and characterisation of bipyridyl(pyridyl)methane type ligands and the corresponding ruthenium(II) bistridentate polypyridyl complexes is described. The bipyridyl-pyridyl methane type ligands were designed to increase the excited state lifetime of ruthenium(II) bisterpyridine-type complexes by altering the ligand field as compared to normal terpyridine ligands.

In the second part photoinduced electron transfer and formation of charge separated states in donor-photosensitizer dyads or donor-photosensitizer-acceptor triads is studied. The first covalently linked donor-photosensitizer-acceptor triad with tyrosine as electron donor was prepared, and long lived light induced charge separation was observed. RuIIterpyridine complexes linked to carotenoid or tyrosine were also prepared, for studies of light induced charge separation on a TiO2 surface. Tryptofan was covalently linked to Ru(bpy)3 and proton coupled electron transfer from tryptophan to photogenerated ruthenium(III) was demonstrated. A pH-dependent study of the electron transfer rate gave insight into the mechanism of proton coupled electron transfer in amino acids.

Finally, the last part of the thesis presents the preparation and properties of the first complex containing a photosensitizer covalently linked to a Fe-hydrogenase active site model.

Place, publisher, year, edition, pages
Stockholm: Institutionen för organisk kemi , 2005. , 54 p.
Keyword [en]
Ruthenium complexes
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-417ISBN: 91-7155-031-3 (print)OAI: oai:DiVA.org:su-417DiVA: diva2:193626
Public defence
2005-04-18, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 14:00
Opponent
Supervisors
Available from: 2005-03-23 Created: 2005-03-23 Last updated: 2014-02-24Bibliographically approved
List of papers
1. A tridentate ligand for preparation of bisterpyridine-like ruthenium(II) complexes with an increased excited state lifetime
Open this publication in new window or tab >>A tridentate ligand for preparation of bisterpyridine-like ruthenium(II) complexes with an increased excited state lifetime
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2004 In: Inorganic Chemistry Communications, ISSN 1387-7003, Vol. 7, no 3, 337-340 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-23636 (URN)
Note
Part of urn:nbn:se:su:diva-417Available from: 2005-03-23 Created: 2005-03-23Bibliographically approved
2. A New Strategy for Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes. Synthesis, Photophysical and Electrochemical characterisation of Six Mononuclear Ruthenium(II) Bisterpyridine Type Complexes
Open this publication in new window or tab >>A New Strategy for Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes. Synthesis, Photophysical and Electrochemical characterisation of Six Mononuclear Ruthenium(II) Bisterpyridine Type Complexes
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2005 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, no 9, 3215-3225 p.Article in journal (Refereed) Published
Abstract [en]

The synthesis and characterization of six ruthenium(II) bistridentate polypyridyl complexes is described. These were designed on the basis of a new approach to increase the excited-state lifetime of ruthenium(II) bisterpyridine-type complexes. By the use of a bipyridylpyridyl methane ligand in place of terpyridine, the coordination environment of the metal ion becomes nearly octahedral and the rate of deactivation via ligand-field (i.e., metal-centered) states was reduced as shown by temperature-dependent emission lifetime studies. Still, the possibility to make quasi-linear donor−ruthenium−acceptor triads is maintained in the complexes. The most promising complex shows an excited-state lifetime of τ = 15 ns in alcohol solutions at room temperature, which should be compared to a lifetime of τ = 0.25 ns for [Ru(tpy)2]2+. The X-ray structure of the new complex indeed shows a more octahedral geometry than that of [Ru(tpy)2]2+. Most importantly, the high excited-state energy was retained, and thus, so was the potential high reactivity of the excited complex, which has not been the case with previously published strategies based on bistridentate complexes.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:su:diva-23637 (URN)10.1021/ic048247a (DOI)000228813400036 ()
Available from: 2005-03-23 Created: 2005-03-23 Last updated: 2017-12-13Bibliographically approved
3. Ruthenium complexes of a bipyridyl(pyridyl)methane ligand: Effect of substituents at the methylene group on structure and photophysics
Open this publication in new window or tab >>Ruthenium complexes of a bipyridyl(pyridyl)methane ligand: Effect of substituents at the methylene group on structure and photophysics
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Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-23638 (URN)
Note
Part of urn:nbn:se:su:diva-417Available from: 2005-03-23 Created: 2005-03-23 Last updated: 2010-01-13Bibliographically approved
4. Intramolecular charge separation in a hydrogen bonded tyrosine-ruthenium(II)-naphtalene diimide triad
Open this publication in new window or tab >>Intramolecular charge separation in a hydrogen bonded tyrosine-ruthenium(II)-naphtalene diimide triad
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2004 In: Chemical Communications, ISSN 1359-7345, no 2, 194-195 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-23639 (URN)
Note
Part of urn:nbn:se:su:diva-417Available from: 2005-03-23 Created: 2005-03-23Bibliographically approved
5. A New Strategy for Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes. Synthesis, Photophysical and Electrochemical characterisation of Six Mononuclear Ruthenium(II) Bisterpyridine Type Complexes
Open this publication in new window or tab >>A New Strategy for Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes. Synthesis, Photophysical and Electrochemical characterisation of Six Mononuclear Ruthenium(II) Bisterpyridine Type Complexes
Show others...
2005 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, no 9, 3215-3225 p.Article in journal (Refereed) Published
Abstract [en]

The synthesis and characterization of six ruthenium(II) bistridentate polypyridyl complexes is described. These were designed on the basis of a new approach to increase the excited-state lifetime of ruthenium(II) bisterpyridine-type complexes. By the use of a bipyridylpyridyl methane ligand in place of terpyridine, the coordination environment of the metal ion becomes nearly octahedral and the rate of deactivation via ligand-field (i.e., metal-centered) states was reduced as shown by temperature-dependent emission lifetime studies. Still, the possibility to make quasi-linear donor−ruthenium−acceptor triads is maintained in the complexes. The most promising complex shows an excited-state lifetime of τ = 15 ns in alcohol solutions at room temperature, which should be compared to a lifetime of τ = 0.25 ns for [Ru(tpy)2]2+. The X-ray structure of the new complex indeed shows a more octahedral geometry than that of [Ru(tpy)2]2+. Most importantly, the high excited-state energy was retained, and thus, so was the potential high reactivity of the excited complex, which has not been the case with previously published strategies based on bistridentate complexes.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:su:diva-23637 (URN)10.1021/ic048247a (DOI)000228813400036 ()
Available from: 2005-03-23 Created: 2005-03-23 Last updated: 2017-12-13Bibliographically approved
6. Electron transfer studies of terpyridine based ruthenium(II)-donor dyads attached to nanostructured TiO2
Open this publication in new window or tab >>Electron transfer studies of terpyridine based ruthenium(II)-donor dyads attached to nanostructured TiO2
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Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-23640 (URN)
Note
Part of urn:nbn:se:su:diva-417Available from: 2005-03-23 Created: 2005-03-23 Last updated: 2010-01-13Bibliographically approved
7. Switching the redox mechanism: Models for proton coupled electron transfer from tyrosine and tryptophan
Open this publication in new window or tab >>Switching the redox mechanism: Models for proton coupled electron transfer from tyrosine and tryptophan
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2005 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, no 11, 3855-3863 p.Article in journal (Refereed) Published
Abstract [en]

The coupling of electron and proton transfer is an important controlling factor in radical proteins, such as photosystem II, ribinucleotide reductase, cytochrome oxidases, and DNA photolyase. This was investigated in model complexes in which a tyrosine or tryptophan residue was oxidized by a laser-flash generated trisbipyridine-Ru-III moiety in an intramolecular, proton-coupled electron transfer (PCET) reaction. The PCET was found to proceed in a competition between a stepwise reaction, in which electron transfer is followed by deprotonation of the amino acid radical (ETPT), and a concerted reaction, in which both the electron and proton are transferred in a single reaction step (CEP). Moreover, we found that we could analyze the kinetic data for PCET by Marcus' theory for electron transfer. By altering the solution pH, the strength of the Ru-III oxidant, or the identity of the amino acid, we could induce a switch between the two mechanisms and obtain quantitative data for the parameters that control which one will dominate. The characteristic pH-dependence of the CEP rate (M. Sjodin et al. J. Am. Chem. Soc. 2000, 122, 3932) reflects the pH-dependence of the driving force caused by proton release to the bulk. For the pH-independent ETPT on the other hand, the driving force of the rate-determining ET step is pH-independent and smaller. On the other hand, temperature-dependent data showed that the reorganization energy was higher for CEP, while the pre-exponential factors showed no significant difference between the mechanisms. Thus, the opposing effect of the differences in driving force and reorganization energy determines which of the mechanisms will dominate. Our results show that a concerted mechanism is in general quite likely and provides a low-barrier reaction pathway for weakly exoergonic reactions. In addition, the kinetic isotope effect was much higher for CEP (k(H)/k(D) > 10) than for ETPT (k(H)/k(D) = 2), consistent with significant changes along the proton reaction coordinate in the rate-determining step of CEP.

Keyword
ATOM TRANSFER-REACTIONS, PHOTOSYSTEM-II, RADICAL ENZYMES, OXIDATION, PROTEINS, COMPLEX, REDUCTION, CHEMISTRY, CATALYSIS, PHENOXYL
National Category
Other Basic Medicine
Identifiers
urn:nbn:se:su:diva-23641 (URN)10.1021/ja044395o (DOI)
Available from: 2005-03-23 Created: 2005-03-23 Last updated: 2017-12-13Bibliographically approved
8. Synthesis and Properties of an Iron Hydrogenase Active Site Model Linked to Ruthenium tris-Bipyridine Photosensitizer
Open this publication in new window or tab >>Synthesis and Properties of an Iron Hydrogenase Active Site Model Linked to Ruthenium tris-Bipyridine Photosensitizer
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2003 In: Inorganic Chemical Communications, Vol. 6, 989-991 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-23642 (URN)
Note
Part of urn:nbn:se:su:diva-417Available from: 2005-03-23 Created: 2005-03-23Bibliographically approved

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