科研之友
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摘要
All-trans retinal is the chromophore of microbial rhodopsins initiating energy conversion and cellular signalling by subpicosecond photoinduced switching. Here, we provide detailed UV-Vis transient absorption experiments to disentangle the complex photochemistry of this polyene, which is governed by its terminal aldehyde group. After photoexcitation to the S-2(B-1(u)+) state, the system exhibits polarity-dependent branching, populating separate S-1((1)A(g)(-)) and intramolecular charge transfer (ICT) species. In all solvents, population of a singlet n pi* state from S-1 is observed which represents the precursor of the T-1 triplet state. While triplet formation dominates in nonpolar solvents (67% quantum yield), it is dramatically reduced in polar solvents (4%). The channel closes completely upon replacing the aldehyde by a carboxyl group, due to an energetic up-shift of (1)n pi*. In that case, internal conversion via the ICT species becomes the main pathway, with preferential formation of the initially excited isomer.
- 出版日期2016-6-14
