Blending Through-Space and Through-Bond 蟺鈥撓€-Coupling in [2,2鈥瞉-Paracyclophane-oligophenylenevinylene Molecular Wires

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• 作者：Mateusz Wielopolski ; Agust铆n Molina-Ontoria ; Christina Schubert ; Johannes T. Margraf ; Evangelos Krokos ; Johannes Kirschner ; Andreas Gouloumis ; Timothy Clark ; Dirk M. Guldi ; Nazario Mart铆n
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：July 17, 2013
• 年：2013
• 卷：135
• 期：28
• 页码：10372-10381
• 全文大小：566K
• 年卷期：v.135,no.28(July 17, 2013)
• ISSN：1520-5126

文摘

A series of ZnP-pCp-oPPV-C₆₀ conjugates covalently connected through [2,2鈥瞉-paracyclophane-oligophenylenevinylene (pCp-oPPV) bridges containing one, two, and three [2,2鈥瞉-paracyclophanes (pCps) has been prepared in multistep synthetic procedures involving Horner鈥揥adsworth鈥揈mmons olefination reactions and/or Heck type Pd-catalyzed reactions. Molecular modeling suggests that charge transfer is effectively mediated by the pCp-oPPVs through a predominant hole-transfer mechanism. Photophysical investigation supports molecular modeling and reveals two major trends. On one hand, C₆₀ excitation of 1, 2, and 3 leads exclusively to charge transfer between pCp and C₆₀ to afford a ZnP-(pCp-oPPV)^鈥?-C₆₀^{鈥⑩€?/sup> radical ion pair state without giving rise to a subsequent charge shift to yield the ZnP鈥?-pCp-oPPV-C₆₀鈥⑩€?/sup> radical ion pair state. On the other hand, ZnP excitation of 1, 2, and 3 results in a rather slow charge transfer between ZnP and C₆₀, after which the ZnP鈥?-pCp-oPPV-C₆₀鈥⑩€?/sup> radical ion pair state evolves. In temperature-dependent ZnP fluorescence experiments, which were performed in the temperature range from 273 to 338 K, two domains are discernible: low and high temperature behaviors. In the low temperature range (i.e., below 30 掳C) the rate constants do not change, suggesting that a superexchange mechanism is the modus operandi. In the high temperature range (i.e., >30 掳C) the rate constants increase. Moreover, we find rather strong distance dependence for 1 and 2 and weak distance dependence for 2 and 3. A damping factor of 0.145 脜鈥? is derived for the former pair and 0.012 脜鈥? for the latter.}