Insights into the Effect of the Ketylimine Group on the Fluorescence Deactivation of Oligofluorenes

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• 作者：Stphane Dufresne ; Ivan Ulliel Roche ; Thomas Skalski ; W. G. Skene
• 刊名：Journal of Physical Chemistry C
• 出版年：2010
• 出版时间：August 5, 2010
• 年：2010
• 卷：114
• 期：30
• 页码：13106-13112
• 全文大小：326K
• 年卷期：v.114,no.30(August 5, 2010)
• ISSN：1932-7455

文摘

A series of oligofluorenes containing arylketylimines in the 9-position ranging between 1 and 3 fluorene segments was prepared. The conjugated ketylimines were prepared using dehydration and Lewis acid protocols from the corresponding oligofluorenones. These heteroconjugated oligomers were prepared for examining the effect of the ketylimine moiety on the photophysical properties relative to their ketone counterparts. Both the ketylimine and fluorenone containing oligofluorenes exhibited reduced fluorescence relative to their corresponding all-fluorene analogues. Temperature-dependent emission measurements and steady-state fluorescence quenching confirmed that fluorescence deactivation of the ketylimines occurred predominately by intramolecular photoinduced electron transfer (PET). This is in contrast to their oligofluorenone counterparts that dissipated their singlet excited state energy via both intersystem crossing and nonradiative internal conversion. The measured diffusion controlled fluorescence quenching rate constants (3 × 10¹⁰ M⁻¹ s⁻¹) combined with the calculated exergonic energetics ranging from −10 to −116 kJ/mol derived from the Rehm−Weller equation for the oligofluorenyl ketylimines corroborate that the ketylimines’ fluorescence deactivation occurs by intramolecular PET.