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Lookup NU author(s): Professor Andrew Benniston,
Emeritus Professor Anthony Harriman,
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An electroactive luminescent switch has been synthesized that comprises a hydroquinone-functionalized 2,2′:6′,2″-terpyridine ligand coordinated to a ruthenium(II) (4′-phenytethynyl-2,2′:6′, 2″-terpyridine) fragment. The assembly is sufficiently rigid that the hydroquinone-chromophore distance is fixed. Excitation of the complex via the characteristic metal-to-ligand charge-transfer (MLCT) absorption band produces an excited triplet state in which the promoted electron is localized on the terpyridine ligand bearing the acetylenic group. The triplet lifetime in butyronitrile solution at room temperature is 46 ± 3 ns but increases markedly at lower temperature. Oxidation of the hydroquinone to the corresponding benzoquinone switches on an electron-transfer process whereby the MLCT triplet donates an electron to the quinone. This reaction reduces the triplet lifetime to 190 ± 12 ps and essentially extinguishes emission. The rate of electron transfer depends on temperature in line with classical Marcus theory, allowing calculation of the electronic coupling matrix element and the reorganization energy as being 22 cm-1 and 0.84 eV, respectively. The switching behavior can be monitored using luminescence spectroelectrochemistry. The on/off level is set by temperature and increases as the temperature is lowered. © 2005 American Chemical Society.
Author(s): Benniston AC, Chapman GM, Harriman A, Rostron SA
Publication type: Article
Publication status: Published
Journal: Inorganic Chemistry
ISSN (print): 0020-1669
ISSN (electronic): 1520-510X
Publisher: American Chemical Society
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