Donor-Acceptor-Substituted Tetrakis(phenylethynyl)benzenes as Emissive Molecules during Pulse Radiolysis in Benzene

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• 作者：Shingo Samori ; Sachiko Tojo ; Mamoru Fujitsuka ; Eric L. Spitler ; Michael M. Haley ; and ; Tetsuro Majima
• 刊名：Journal of Organic Chemistry
• 出版年：2007
• 出版时间：April 13, 2007
• 年：2007
• 卷：72
• 期：8
• 页码：2785 - 2793
• 全文大小：463K
• 年卷期：v.72,no.8(April 13, 2007)
• ISSN：1520-6904

文摘

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Emission from charge recombination between radical cations and anions of various tetrakis(phenylethynyl)benzenes (TPEBs) was measured during pulse radiolysis in benzene (Bz). The formation of TPEB in thesinglet excited state (¹TPEB^*) can be attributed to the charge recombination between TPEB^{ges/entities/bull.gif">+} and TPEB^{ges/entities/bull.gif">-},which are initially generated from the radiolytic reaction in Bz. This mechanism is reasonably explainedby the relationship between the annihilation enthalpy change (-ges/gifchars/Delta.gif" BORDER=0 >Hges/entities/deg.gif">) for the charge recombination ofTPEB^{ges/entities/bull.gif">+} and TPEB^{ges/entities/bull.gif">-} and excitation energy of ¹TPEB^*. It was found that the charge recombination betweenTPEB^{ges/entities/bull.gif">+} and TPEB^{ges/entities/bull.gif">-} occurred to give ¹TPEB^* as the emissive species, but not the excimers because ofthe large repulsion between substituents caused by the rotation around C-C single bonds of TPEBs.Since donor-acceptor-substituted TPEBs possess three types of charge-transfer pathways (linear-conjugated, cross-conjugated, and "bent" conjugated pathways between the donor and acceptor substituentsthrough the ethynyl linkage), the emission spectra of ¹TPEBs^* with intramolecular charge transfer (ICT)character depend on the substitution pattern and the various kinds of donor and acceptor groups duringpulse radiolysis in Bz.