Shielding of Electron Acceptors Coordinated to Rhenium(I) by Carboxylato Groups. Intraligand and Charge‐Transfer Excited‐State Properties of fac‐(‘Anthraquinone‐2‐carboxylato')(2,2′‐bipyridine)tricarbonylrhenium (fac‐[ReI(aq‐2‐CO2)(2,2′‐bipy)(CO)3]) |
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Authors: | GustavoT Ruiz MariaP Juliarena ReynaldoO Lezna Ezequiel Wolcan MarioR Feliz Guillermo Ferraudi |
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Abstract: | The photophysical and photochemical properties of (OC‐6‐33)‐(2,2′‐bipyridine‐κN1,κN1′)tricarbonyl(9,10‐dihydro‐9,10‐dioxoanthracene‐2‐carboxylato‐κO)rhenium (fac‐ReI(aq‐2‐CO2)(2,2′‐bipy)(CO)3]) were investigated and compared to those of the free ligand 9,10‐dihydro‐9,10‐dioxoanthracene‐2‐carboxylate (=anthraquinone‐2‐carboxylate) and other carboxylato complexes containing the (2,2′‐bipyridine)tricarbonylrhenium (Re(2,2′‐bipy)(CO)3]) moiety. Flash and steady‐state irradiations of the anthraquinone‐derived ligand (λexc 337 or 351 nm) and of its complex reveal that the photophysics of the latter is dominated by processes initiated in the Re‐to‐(2,2′‐bipyridine) charge‐transfer excited state and 2,2′‐bipyridine‐ and (anthraquinone‐2‐carboxylato)‐centered intraligand excited states. In the reductive quenching by N,N‐diethylethanamine (TEA) or 2,2′,2″‐nitrilotrisethanol] TEOA, the reactive states are the 2,2′‐bipyridine‐centered and/or the charge‐transfer excited states. The species with a reduced anthraquinone moiety is formed by the following intramolecular electron transfer, after the redox quenching of the excited state: ReI(aq?2?CO2)(2,2′‐bipy.)(CO)3]??ReI(aq?2?CO2.)(2,2′‐bipy)(CO)3]? The photophysics, particularly the absence of a ReI‐to‐anthraquinone charge‐transfer excited state photochemistry, is discussed in terms of the electrochemical and photochemical results. |
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