Excited-State Processes in First-Generation Phenyl-Cored Thiophene Dendrimers

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• 作者：Allison C. Kanarr ; Benjamin L. Rupert ; Scott Hammond ; Jao van de Lagemaat ; Justin C. Johnson ; Andrew J. Ferguson
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：March 31, 2011
• 年：2011
• 卷：115
• 期：12
• 页码：2515-2522
• 全文大小：1045K
• 年卷期：v.115,no.12(March 31, 2011)
• ISSN：1520-5215

文摘

First generation dendrimers with three oligothiophene arms (meta-arranged, 3G1-nS) and four arms (ortho- and para-arranged, 4G1-nS) connected to a central phenyl core were investigated spectroscopically in solution. In all dendrimers, on an ultrafast time scale (<10 ps), two 鈥渃ooling鈥?processes convert the initially generated, 鈥渉ot鈥?exciton into the geometrically relaxed, 鈥渃old鈥?exciton. A decrease in the triplet yield, particularly evident for the 4-arm dendrimers; intersystem crossing rate; and nonradiative triplet decay time with increasing number of bridging thiophene units n all meet with expectations from prior studies on linear oligothiophenes. A relatively fast internal conversion process (>0.6 ns<sup>鈭?sup>) is observed in both dendrimer series, possibly due to increased twisting about the phenyl core that reduces the triplet yields considerably with respect to oligothiophenes. An anomalous shifting of the triplet鈭抰riplet absorption spectra characterizes the 4G1-nS dendrimers as unique from the 3G1-nS series in terms of the hindrance of torsional motion and confinement of excited states enforced by the arrangement of dendrons.