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Title: Variation of Excited-State Dynamics in Trifluoromethyl Functionalized C60 Fullerenes

We report on electronically excited-state dynamics of three different trifluoromethyl C60 fullerenes (TMFs, C60(CF3)n: C60/4-1, C60/6-2, and C60/10-1, featuring four, six, and ten trifluoromethyl groups, respectively) using steady-state and time-resolved optical spectroscopy as well as ultrafast pump/probe transient absorption spectroscopy. C60/4-1 and C60/6-2 dissolved in toluene solvent show near-unity S1--T1 intersystem crossing quantum yield (..phi..ISC), ca. 1 ns S1-state lifetimes, and microsecond-timescale T1-state lifetimes, which are typical of the fullerene class. On the other hand, C60/10-1 exhibits a dominant sub-nanosecond nonradiative S1--S0 relaxation mechanism and negligible ..phi..ISC, therefore decreasing the average excited-state lifetime (..tau..avg) by about 5 orders of magnitude compared to that of C60/4-1 and C60/6-2 (..tau..avg approx. 17 us and 54 us for C60/4-1 and C60/6-2, respectively, whereas ..tau..avg approx. 100 ps for C60/10-1). These excited-state characteristics of C60/4-1 and C60/6-2 are preserved in polymer matrix, suggesting that fullerene/polymer interactions do not modulate intrinsic photophysics of trifluoromethyl-substituted fullerenes. The contrasting excited- state study results of C60/4-1 and C60/6-2 to that of C60/10-1 infer that intrinsic optical properties and excited-state dynamics can be affected by the substitution on the fullerene.
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Resource Type:
Journal Article
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Journal Name: Physical Chemistry Chemical Physics; Journal Volume: 18; Journal Issue: 33
Research Org:
NREL (National Renewable Energy Laboratory (NREL), Golden, CO (United States))
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY fullerenes; transient absorption spectroscopy; excited-state dynamics