溶液中双稳态偶氮苯衍生物的双光子诱导与单光子诱导异构化动力学
Two-Photon-Induced versus One-Photon-Induced Isomerization Dynamics of a Bistable Azobenzene Derivative in Solution.
作者信息
Moreno J, Gerecke M, Dobryakov A L, Ioffe I N, Granovsky A A, Bléger D, Hecht S, Kovalenko S A
机构信息
Department of Chemistry, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
Department of Chemistry, Lomonosov Moscow State University , 119991 Moscow, Russia.
出版信息
J Phys Chem B. 2015 Sep 17;119(37):12281-8. doi: 10.1021/acs.jpcb.5b07008. Epub 2015 Sep 8.
We report on a bistable azobenzene derivative with sufficiently high 2-photon absorption to induce its photochemical isomerization and measurable excited state dynamics. Broadband transient absorption spectra were recorded and compared upon 1-photon (331 nm) and 2-photon (640 nm) excitation of the S0 → S2 transition. The spectra are different at early (t ∼ 1 ps) and late (t ∼ 100 ps) time but show similar photoisomerization behavior on a 10 ps time scale. With 2-photon excitation, strong population transfer S2 → Sn occurs due to resonance absorption of a third pump photon. Subsequent internal conversion Sn → S1 results in a very hot S1 population causing extra-broadening of the transient spectra. The resonance pump absorption is common with nonlinear excitation and should be taken into account when considering photochemical applications. The 2-photon excitation cross-section σ((2)) at 640 nm was measured to be 7 GM for the specific tetra-ortho-fluorinated azobenzene derivative and 1 GM for unsubstituted parent azobenzene. The direct 2-photon induced trans-to-cis isomerization, described herein, provides an unprecedented potential for spatially addressing P-type (bistable) azobenzene photoswitches in 3D.
我们报道了一种具有足够高双光子吸收的双稳态偶氮苯衍生物，能够诱导其光化学异构化并具有可测量的激发态动力学。记录了宽带瞬态吸收光谱，并在单光子（331 nm）和双光子（640 nm）激发S0→S2跃迁时进行了比较。光谱在早期（t ∼ 1 ps）和晚期（t ∼ 100 ps）不同，但在10 ps时间尺度上显示出相似的光异构化行为。通过双光子激发，由于第三个泵浦光子的共振吸收，会发生强烈的S2→Sn的布居转移。随后的内转换Sn→S1导致非常热的S1布居，引起瞬态光谱的额外展宽。共振泵浦吸收在非线性激发中很常见，在考虑光化学应用时应予以考虑。对于特定的四邻位氟化偶氮苯衍生物，在640 nm处测量的双光子激发截面σ((2))为7 GM，对于未取代的母体偶氮苯为1 GM。本文所述的直接双光子诱导的反式到顺式异构化在三维空间中对P型（双稳态）偶氮苯光开关进行空间寻址方面提供了前所未有的潜力。
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