title: Two-Photon-Induced versus One-Photon-Induced Isomerization Dynamics of a Bistable Azobenzene Derivative in Solution.
abstract: 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.
authors: Department of Chemistry, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors: J
authors: J
authors: Moreno
authors: Department of Chemistry, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors: M
authors: M
authors: Gerecke
authors: Department of Chemistry, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors: A L
authors: AL
authors: Dobryakov
authors: Department of Chemistry, Lomonosov Moscow State University , 119991 Moscow, Russia.
authors: I N
authors: IN
authors: Ioffe
authors: Firefly Project , 117593 Moscow, Russia.
authors: A A
authors: AA
authors: Granovsky
authors: Department of Chemistry, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors: D
authors: D
authors: Bléger
authors: Department of Chemistry, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors: S
authors: S
authors: Hecht
authors: Department of Chemistry, Humboldt-Universität zu Berlin , Brook-Taylor-Strasse 2, 12489 Berlin, Germany.
authors: S A
authors: SA
authors: Kovalenko