Probing the intrachain and interchain effects on the fluorescence behavior of pentiptycene-derived oligo(p-phenyleneethynylene)s

Jye Shane Yang, Jyu Lun Yan, Chung Yu Hwang, Shih Yi Chiou, Kang Ling Liau, Hui Hsu Gavin Tsai, Gene Hsiang Lee, Shie Ming Peng

Research output: Contribution to journalArticlepeer-review

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The synthesis, crystal structure, and fluorescence behavior of acetylene-bridged pentiptycene dimer (2), trimer (3), and tetramer (4) are reported. For comparison, a phenylene-pentiptycene-phenylene three-ring system (5) is also investigated. As a result of the unique intrachain pentiptycene-pentiptycene interactions in 3 and 4, their twisted conformers are populated in polar solvents and at low temperatures, and the phenomenon of nonequilibration of excited rotational conformers is observed. Twisting of the π-conjugated backbones leads to blue-shifted absorption and fluorescence spectra and increased fluorescence quantum yields and lifetimes. The fluorescence spectra of 2-4 undergo small red shifts but large intensity variations in the 0-1 vs 0-0 bands on going from,solutions to thin solid films, which can be accounted for by the reabsorption effect. However, the reduction in fluorescence quantum yields for 2-4 in films vs solutions is mainly attributed to efficient interchain exciton migration to nonfluorescent energy traps. In contrast, the behavior of nonequilibration of excited rotamers is not observed for 5 in solutions. Compound 5 forms J-type aggregates through terminal phenylene π-stackings in the solid state, resulting in a new absorption band at 377 nm and large red shifts of the structured fluorescence spectra.

Original languageEnglish
Pages (from-to)14109-14119
Number of pages11
JournalJournal of the American Chemical Society
Issue number43
StatePublished - 1 Nov 2006


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