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Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kvantkemi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
Vise andre og tillknytning
2008 (engelsk)Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 47, nr 9, s. 3540-3548Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The structural effect on the metal-to-ligand charge transfer (MLCT) excited-state lifetime has been investigated in bis-tridentate Ru(II)-polypyridyl complexes based on the terpyridine-like ligands [6-(2,2'-bipyridyl)](2-pyridyl)methane (1) and 2-[6-(2,2'-bipyridyl)]-2-(2-pyridyl)propane (2). A homoleptic ([Ru(2)(2)](2+)) and a heteroleptic complex ([Ru(ttpy)(2)](2+)) based on the new ligand 2 have been prepared and their photophysical and structural properties studied experimentally and theoretically and compared to the results for the previously reported [Ru(1)(2)](2+). The excited-state lifetime of the homoleptic Ru-II complex with the isopropylene-bridged ligand 2 was found to be 50 times shorter than that of the corresponding homoleptic Ru-II complex of ligand 1, containing a methylene bridge. A comparison of the ground-state geometries of the two homoleptic complexes shows that steric interactions involving the isopropylene bridges make the coordination to the central Ru-II ion less octahedral in [Ru(2)(2)](2+) than in [Ru(1)(2))(2+). Calculations indicate that the structural differences in these complexes influence their ligand field splittings as well as the relative stabilities of the triplet metal-to-ligand charge transfer ((MLCT)-M-3) and metal-centered ((MC)-M-3) excited states. The large difference in measured excited-state lifetimes for the two homoleptic Ru-II complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (MLCT)-M-3 states to short-lived (MC)-M-3 states.

sted, utgiver, år, opplag, sider
ACS , 2008. Vol. 47, nr 9, s. 3540-3548
HSV kategori
Forskningsprogram
Analytisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-95085DOI: 10.1021/ic7019457ISI: 000255380500018PubMedID: 18402440OAI: oai:DiVA.org:uu-95085DiVA, id: diva2:169161
Tilgjengelig fra: 2006-11-09 Laget: 2006-11-09 Sist oppdatert: 2017-12-14bibliografisk kontrollert
Inngår i avhandling
1. Tuning of the Excited State Properties of Ruthenium(II)-Polypyridyl Complexes
Åpne denne publikasjonen i ny fane eller vindu >>Tuning of the Excited State Properties of Ruthenium(II)-Polypyridyl Complexes
2006 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Processes where a molecule absorbs visible light and then converts the solar energy into chemical energy are important in many biological systems, such as photosynthesis and also in many technical applications e.g. photovoltaics. This thesis describes a part of a multidisciplinary project, aiming at a functional mimic of the natural photosynthesis, with the overall goal of production of a renewable fuel from sun and water. More specific, the thesis is focused on design and photophysical characterization of new photosensitizers, i.e. light absorbers that should be capable of transferring electrons to an acceptor and be suitable building blocks for supramolecular rod-like donor-photosensitizer-acceptor arrays.

The excited state lifetime, the excited state energy and the geometry are important properties for a photosensitizer. The work presented here describes a new strategy to obtain longer excited state lifetimes of the geometrically favorable Ru(II)-bistridentate type complexes, without a concomitant substantial decrease in excited state energy. The basic idea is that a more octahedral coordination around the Ru will lead to longer excited state lifetimes. In the first generation of new photosensitizers a 50-fold increase of the excited state lifetime was observed, going from 0.25 ns for the model complex to 15 ns for the best photosensitizer. The second generation goes another step forward, to an excited state lifetime of 810 ns. Furthermore, the third generation of new photosensitizers show excited state lifetimes in the 0.45 - 5.5 microsecond region at room temperature, a significant improvement. In addition, the third generation of photosensitizers are suitable for further symmetric attachment of electron donor and acceptor motifs, and it is shown that the favorable properties are maintained upon the attachment of anchoring groups. The reactivity of the excited state towards light-induced reactions is proved and the photostability is sufficient so the new design strategy has proven successful.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis, 2006. s. 79
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 237
Emneord
Physical chemistry, Artificial photosynthesis, Ruthenium(II), Bistridentate complexes, Excited state lifetime, Linear donor-photosenstizer-acceptor arrays, Temperature dependence, Excited state decay, Fysikalisk kemi
Identifikatorer
urn:nbn:se:uu:diva-7230 (URN)91-554-6707-5 (ISBN)
Disputas
2006-12-01, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30
Opponent
Veileder
Tilgjengelig fra: 2006-11-09 Laget: 2006-11-09 Sist oppdatert: 2011-06-10bibliografisk kontrollert

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