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光致异构化是分子光物理与光化学反应的核心, 其量子产率与激发态动力学演化路径相关. 改变分子激发态演化路径以实现对光化学反应的精准操控是物理学家、化学家长期以来追求的梦想. 本文采用飞秒泵浦-受激亏蚀-探测(pump-dump-probe)光谱技术, 研究了受激亏蚀光脉冲对1, 1'-二乙基-2, 2'-碘化菁(1, 1'-diethyl-2, 2'-cyanine iodide, 1122C)分子光异构化动力学的影响. 在泵浦-探测(pump-probe)实验中, 1122C分子被泵浦光激发之后, 处于激发态的分子以5.6 ps的时间常数沿扭转反应坐标发生结构变化, 从反式(trans-)构型转变为顺式(cis-)构型. 为了对该反应进行人为调控, 本文在传统泵浦-探测光谱的基础上, 引入第3束波长为1030 nm的飞秒受激亏蚀光. 受激亏蚀光脉冲成功使部分处于激发态的反式构型分子通过受激跃迁直接返回基态, 绕过了原本通向顺式产物的异构化通道. 通过比较顺式产物吸收信号的变化, 计算得出受激亏蚀光作用下顺式构型的产率降低了约12.1%. 本文研究实现了利用飞秒激光对超快光化学反应路径的主动干预, 展示了飞秒多脉冲光谱技术在调控分子激发态演化路径、优化光异构化反应产率的潜力. 该研究为将来对复杂光化学反应精准操控提供了理论和技术支持.
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关键词:
- 飞秒瞬态吸收光谱 /
- 光异构化 /
- 激发态动力学 /
- 泵浦-受激亏蚀-探测
Photoisomerization is a prototypical photophysical and photochemical reaction, and the reaction quantum yield depends on its excited-state dynamic. Changing the evolution path of molecular excited states to achieve precise control over photochemical reactions has long been a dream pursued by physicists and chemists. To investigate the effect of femtosecond laser pulse on the ultrafast reaction, the ultrafast photoisomerization of 1, 1'-diethyl-2, 2'-cyanine iodide (1122C) in methanol is studied using pump-dump-probe spectroscopy. A third femtosecond pulse (Dump) at 1030 nm, which is delayed by 1 ps relative to the initial pump pulse, is introduced into the traditional pump-probe experiment. The recovery of ground state bleaching (GSB) and decrease of the cis product are observed in the pump-dump-probe experiment. It indicates that the dump pulse successfully promotes the initial transform: skipping the trans-cis isomerization pathway in the excited state and returning to the ground state directly through stimulated emission. It is found that the cis yield is reduced by approximately 12.1% under irradiation of the dump pulse. Our research shows that the quantum yields of a typic ultrafast photoisomerization reaction is successfully regulated by using femtosecond laser pulse, demonstrating the potential of femtosecond multi-pulse spectroscopy in modifying excited-state evolution pathways and optimizing photochemical reaction yields. This study provides theoretical and technical support for precisely controlling complex photochemical reactions in the future.
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Keywords:
- femtosecond transient absorption spectroscopy /
- photoisomerization /
- excited state dynamics /
- pump-dump-probe
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图 1 1122C分子光致异构化示意图
Fig. 1. Schematic diagram of the photo-isomerization process for 1122C.
图 2 泵浦-探测和泵浦-受激亏蚀-探测实验光路图
Fig. 2. Diagram of pump-probe and pump-dump-probe experiments.
图 3 1122C分子甲醇溶液的稳态吸收光谱图(蓝色箭头表示瞬态实验的激发波长450 nm)
Fig. 3. Steady-state absorption spectrum of 1122C in methanol (the blue arrow indicates the 450 nm is selected as the excitation wavelength for the following transient experiment).
图 4 1122C分子甲醇溶液的Pump-Probe实验结果 (a)二维瞬态吸收光谱图(激发波长为450 nm); (b)不同延迟时刻下的瞬态吸收光谱; (c)几个具有代表性的不同探测波长的动力学轨迹; (d)探测波长为550 nm的动力学轨迹以及拟合结果
Fig. 4. (a) Two-dimensional Pump-Probe transient absorption spectrum of 1122C in methanol (pump = 450 nm); (b) time-resolved transient absorption in the different delay times; (c) representative transient absorption kinetic trace for various probe wavelengths; (d) the kinetic curve and fitted results at 550 nm.
图 5 1122C分子激发态波包演化动力学示意图.
Fig. 5. Schematic wavepacket motion in the 1122C photoismerization reaction.
图 6 1122C分子甲醇溶液的泵浦-受激亏蚀-探测实验结果 (a) 二维瞬态吸收光谱图(激发波长为450 nm, 受激亏蚀延迟为1 ps, 受激亏蚀波长为1030 nm); (b), (c) 2 ps和78 ps延迟时刻下受激亏蚀光作用前后的瞬态吸收光谱图(PP为泵浦-探测, PDP为泵浦-受激亏蚀-探测); (d), (e) 探测波长为525 nm和550 nm的DP, PP和PDP动力学曲线(DP为受激亏蚀-探测); (f) 1122C分子在受激亏蚀光作用下波包运动示意图
Fig. 6. Pump-dump-probe transient absorption of 1122C in methanol: (a) Two-dimensional spectrum (pump: 450 nm, dump: 1030 nm, and dump at 1 ps delay time); (b), (c) transient absorption spectra at the 2 ps and 78 ps delay times in the presence (PDP) and absence (PP) of a dump pulse; (d), (e) selected DP, PP and PDP kinetic traces at 525 nm and 550 nm; (f) schematic wavepacket motion of 1122C in the pump-dump-probe experiment.
图 7 泵浦-探测和泵浦-受激亏蚀-探测吸收谱在545 nm的动力学轨迹以及拟合曲线
Fig. 7. Kinetic traces and fitting curves at 545 nm of pump-probe and pump-dump-probe spectra.
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[1] Takeuchi S, Ruhman S, Tsuneda T, Chiba M, Taketsugu T, Tahara T 2008 Science 322 1073
Google Scholar
[2] Kukura P, McCamant D W, Yoon Sangwoon, Wandschneider D B, Mathies R A 2005 Science 310 1006
Google Scholar
[3] Ernst O P, Lodowski D T, Elstner M, Hegemann P, Brown L S, Kandori H 2014 Chem. Rev. 114 126
Google Scholar
[4] Kuramochi H, Takeuchi S, Yonezawa K, Kamikubo H, Kataoka M, Tahara T 2017 Nat. Chem. 9 660
Google Scholar
[5] Quick M, Dobryakov A L, Gerecke M, et al. 2014 J. Phys. Chem. B 118 8756
Google Scholar
[6] Nguyen D T, Freitag M, Gutheil C, et al. 2020 Angew. Chem. Int. Ed. 59 13651
Google Scholar
[7] Roy P, Sardjan A S, Danowski W, Browne W R, Feringa B L, Meech S R 2024 J. Chem. Phys. 161 074504
Google Scholar
[8] Shi Y N, Zhao X Y, Wang C, et al. 2020 Chem. Asian J. 15 1478
Google Scholar
[9] Dietzek B, Brüggemann B, Pascher T, Yartsev A 2006 Phys. Rev. Lett. 97 258301
Google Scholar
[10] Dietzek B, Tarnovsky A N, Yartsev A 2009 Chem. Phys. 357 54
Google Scholar
[11] Rentsch S K 1982 Chem. Phys. 69 81
Google Scholar
[12] Dietz F, Rentsch S K 1985 Chem. Phys. 96 145
Google Scholar
[13] Dietzek B, Yartsev A, Tarnovsky A N 2007 J. Phys. Chem. B 111 4520
Google Scholar
[14] Dietzek B, Brüggemann B, Pascher T, Yartsev A 2007 J. Am. Chem. Soc. 129 13014
Google Scholar
[15] Dietzek B, Pascher T, Yartsev A 2007 J. Phys. Chem. B 111 6034
[16] Wei Z, Nakamura T, Takeuchi S, Tahara T 2011 J. Am. Chem. Soc. 133 8205
Google Scholar
[17] Ma F, Yartsev A 2016 RSC Adv. 6 45210
Google Scholar
[18] Levitus M, Ranjit S 2011 Q. Rev. Biophys. 44 123
Google Scholar
[19] Sun W, Guo S, Hu C, et al. 2016 Chem. Rev. 116 7768
Google Scholar
[20] Shapovalov S A 2022 Colorants 1 165
Google Scholar
[21] Dietzek B, Christensson N, Pascher T, Pullerits T, Yartsev A 2007 J. Phys. Chem. B 111 5396
Google Scholar
[22] Muramatsu S, Tokizane T, Inokuchi Y 2022 J. Phys. Chem. A 126 8127
Google Scholar
[23] Hart S M, Banal J L, Bathe M, Schlau-Cohen G S 2020 J. Phys. Chem. Lett. 11 5000
Google Scholar
[24] Guo C, Aydin M, Zhu H, Akins D L 2002 J. Phys. Chem. B 106 5447
Google Scholar
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