Conjugated fluorenes prepared from azomethines connections--II: The effect of alternating fluorenones and fluorenes on the spectroscopic and electrochemical properties

The Journal of Physical Chemistry. B
Stéphane DufresneW G Skene

Abstract

The photophysics and electrochemistry of fluorene and fluorenone azomethine derivatives were examined in order to understand the deactivation pathways responsible for the quenched fluorescence of these compounds, which should otherwise be fluorescent. Steady-state fluorescence showed that the fluorene singlet excited state is quenched both by fluorenone (1) and a model aliphatic azomethine compound (14) with k(q) approximately 10(10) M(-1) s(-1). The quencher concentration required to deactivate 95% of the excited singlets formed was 8.4 mM for fluorenone and 34 mM for 14. Intramolecular photoinduced electron transfer (PET) from fluorene to both 1 and 14 was found as the principle deactivation mode of the fluorene's excited state. The high degree of conjugation of the azomethines promotes intersystem crossing to the triplet manifold by narrowing the singlet-triplet energy gap, which is also in part responsible for the reduced fluorescence observed for the fluorenone azomethine derivatives 5-11. Fluorescence quenching by PET was corroborated from the electrochemical and spectroscopic data by applying the Rehm-Weller equation. Meanwhile, the inherent fluorene fluorescence can be restored by protonating the azomethine, resulting f...Continue Reading

References

Mar 28, 1996·Chemical Reviews·Neil G. Connelly, William E. Geiger
Jan 5, 2006·Chemistry : a European Journal·Nicolas GiusepponeJean-Marie Lehn
Jan 21, 2006·The Journal of Chemical Physics·Chunyan ChiGerhard Wegner
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Feb 10, 2009·Journal of the American Chemical Society·Timothy T StecklerJohn R Reynolds

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Citations

May 20, 2011·The Journal of Physical Chemistry. a·Leandro A EstradaDouglas C Neckers
Mar 2, 2011·Chemical Communications : Chem Comm·Snigdha PandaSanjio S Zade
Aug 31, 2013·Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy·Agnieszka IwanLukasz Skorka
Aug 4, 2018·Molecules : a Journal of Synthetic Chemistry and Natural Product Chemistry·Fan YangJie Li
May 23, 2012·The Journal of Organic Chemistry·Yanmei DongW G Skene

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