Improving the Efficiency of the Photoinduced Charge-Separation Process in a Rhenium(I)鈥揨inc Porphyrin Dyad by Simple Chemical Functionalization

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• 作者：Teresa Gatti ; Paolo Cavigli ; Ennio Zangrando ; Elisabetta Iengo ; Claudio Chiorboli ; Maria Teresa Indelli
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：March 18, 2013
• 年：2013
• 卷：52
• 期：6
• 页码：3190-3197
• 全文大小：404K
• 年卷期：v.52,no.6(March 18, 2013)
• ISSN：1520-510X

文摘

We demonstrate here that, whereas the rhenium(I)鈥搝inc porphyrin dyad fac-[Re(CO)₃(bpy)(Zn路4鈥睲PyP)](CF₃SO₃) [1; 4鈥睲PyP = 5-(4鈥?pyridyl)-10,15,20-triphenylporphyrin] shows no evidence for photoinduced electron transfer upon excitation in the visible region because the charge-separated state ZnP⁺鈥揜e^{鈥?/sup> is almost isoenergetic with the singlet excited state of the zinc porphyrin (螖G = 鈭?.05 eV), the introduction of electron-withdrawing ethyl ester groups on the bpy ligand significantly improves the thermodynamics of the process (螖G = 鈭?.42 eV). As a consequence, in the new dyad fac-[Re(CO)₃(4,4鈥?DEC-bpy)(Zn路4鈥睲PyP)](CF₃SO₃) (4; 4,4鈥?DEC-bpy = 4,4鈥?diethoxycarbonyl-2,2鈥?bipyridine), an efficient and ultrafast intramolecular electron-transfer process occurs from the excited zinc porphyrin to the rhenium unit upon excitation with visible light. Conversely, the introduction of electron-donor tert-butyl groups on the meso-phenyl moieties of the zinc porphyrin has a negligible effect on the photophysics of the system. For dyad 4, the time constants for the charge-separation and charge-recombination processes in solvents of different polarity (PrCN, DCM, and toluene) were measured by an ultrafast time-resolved absorption technique (位_exc = 560 nm).}