Hole Tunneling and Hopping in a Ru(bpy)(3)(2+)-Phenothiazine Dyad with a Bridge Derived from oligo-p-Phenylene
2011 | journal article. A publication with affiliation to the University of Göttingen.
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- Authors
- Walther, Mathieu E.; Wenger, Oliver S.
- Abstract
- A molecular dyad was synthesized in which a Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) photosensitizer and a phenothiazine redox partner are bridged by a sequence of tetramethoxybenzene, p-dimethoxybenzene, and p-xylene units. Hole transfer from the oxidized metal complex to the phenothiazine was triggered using a flash-quench technique and investigated by transient absorption spectroscopy. Optical spectroscopic and electrochemical experiments performed on a suitable reference molecule in addition to the above-mentioned dyad lead to the conclusion that hole transfer from Ru(bpy)(3)(3+) to phenothiazine proceeds through a sequence of hopping and tunneling steps: Initial hole hopping from Ru(bpy)(3)(3+) to the easily oxidizable tetramethoxybenzene unit is followed by tunneling through the barrier imposed by the p-dimethoxybenzene and p-xylene spacers. The overall charge transfer proceeds with a time constant of 41 ns, which compares favorably to a time constant of 1835 ns associated with equidistant hole tunneling between the same donor acceptor couple bridged by three identical p-xylene units. The combined hopping/tunneling sequence thus leads to an acceleration of hole transfer by roughly a factor of 50 when compared to a pure tunneling mechanism.
- Issue Date
- 2011
- Status
- published
- Publisher
- Amer Chemical Soc
- Journal
- Inorganic Chemistry
- ISSN
- 0020-1669
- Sponsor
- Deutsche Forschungsgemeinschaft [WE4815/1, INST186/872-1]