ic7b03050_si_001.pdf (1.53 MB)
Is π‑Stacking Prone To Accelerate Singlet–Singlet Energy Transfers?
journal contribution
posted on 2018-03-23, 19:19 authored by Di Gao, Shawkat M. Aly, Paul-Ludovic Karsenti, Pierre D. Harveyπ-Stacking
is the most common structural feature that dictates the optical and
electronic properties of chromophores in the solid state. Herein,
a unidirectional singlet–singlet energy-transfer dyad has been
designed to test the effect of π-stacking of zinc(II) porphyrin, [Zn2], as a slipped dimer
acceptor using a BODIPY unit, [bod], as the donor, bridged
by the linker C6H4CCC6H4. The rate of singlet energy transfer, kET(S1), at 298 K (kET(S1) = 4.5 × 1010 s–1) extracted through the change in fluorescence lifetime, τF, of [bod] in the presence (27.1 ps) and the
absence of [Zn2] (4.61 ns) from Streak camera measurements, and the rise time of
the acceptor signal in femtosecond transient absorption spectra (22.0
ps), is faster than most literature cases where no π-stacking
effect exists (i.e., monoporphyrin units). At 77 K, the τF of [bod] increases to 45.3 ps, indicating that kET(S1) decreases by 2-fold (2.2 ×
1010 s–1), a value similar to most values
reported in the literature, thus suggesting that the higher value
at 298 K is thermally promoted at a higher temperature.