Steric Influence on the Excited-State Lifetimes of Ruthenium Complexes with Bipyridyl−Alkanylene−Pyridyl Ligands
| Autor: | Olof Johansson, Hans Christian Becker, Henriette Wolpher, Lars Eriksson, Jonas Bergquist, Torben Rasmussen, Leif Hammarström, Björn Åkermark, Petter Persson, Maria Abrahamsson, Maria J. Lundqvist, Per-Ola Norrby |
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| Rok vydání: | 2008 |
| Předmět: |
Models
Molecular Steric effects Photochemistry Pyridines Molecular Conformation chemistry.chemical_element Oxidation reduction Crystallography X-Ray Ligands Ruthenium Molecular conformation Inorganic Chemistry Propane 2 2'-Dipyridyl chemistry Chemical physics Excited state Organometallic Compounds Quantum Theory Spectrophotometry Ultraviolet Physical and Theoretical Chemistry Methane Oxidation-Reduction |
| Zdroj: | Inorganic Chemistry. 47:3540-3548 |
| ISSN: | 1520-510X 0020-1669 |
| DOI: | 10.1021/ic7019457 |
| Popis: | 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 ( (3)MLCT) and metal-centered ( (3)MC) 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 (3)MLCT states to short-lived (3)MC states. |
| Databáze: | OpenAIRE |
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