Excited-State-Selective Ultrafast Relaxation Dynamics and Photoisomerization of trans -4,4′-Azopyridine
Excited-State-Selective Ultrafast Relaxation Dynamics and Photoisomerization of trans -4,4′-Azopyridine
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反式-4,4-偶氮吡啶的激发态选择性超快弛豫动力学和光异构化
DOI：
10.1021/acs.jpclett.2c02523
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Tarnovsky, Alexander N.
中科院分区：
文献类型：
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作者：
Obloy, Laura M.;El-Khoury, Patrick Z.;Tarnovsky, Alexander N.
使用时间分辨率为 30 fs 的飞秒瞬态吸收研究了反式 4,4'-偶氮吡啶在乙醇中的激发态动力学。以三种不同的波长（460 和 290 (275) nm）激发系统，分别访问 S1nπ* 和 S2ππ* 电子态，揭示了 195 cm–1 振动相干性，这表明相同的模式在 nπ* 和 ππ* 弛豫通道中都处于活动状态。 S1 激发后，弛豫通过非旋转路径进行，其中一部分 thenπ* 粒子被困在平面最小值（寿命，2.1 ps）中，而其余粒子在衰变到基态之前进一步移动到第二个浅极小值（寿命，300 fs）。 S2 态的种群导致 30 fs 非旋转弛豫，同时 nπ* 种群的积累和热基态物种的几乎同时形成。观察到 ππ* 与 nπ* 激发时顺式异构体量子产率增加，这与反式偶氮苯相反。
Excited-state dynamics oftrans-4,4′-azopyridine in ethanol is studied using femtosecond transient absorption with 30 fs temporal resolution. Exciting the system at three different wavelengths, 460 and 290 (275) nm, to access the S1nπ* and S2ππ* electronic states, respectively, reveals a 195 cm–1vibrational coherence, which suggests that the same mode is active in bothnπ* andππ* relaxation channels. Following S1-excitation, relaxation proceeds via a nonrotational pathway, where a fraction of thenπ* population is trapped in a planar minimum (lifetime, 2.1 ps), while the remaining population travels further to a second shallow minimum (lifetime, 300 fs) prior to decay into the ground state. Population of the S2state leads to 30 fs nonrotational relaxation with a concurrent buildup ofnπ* population and nearly simultaneous formation of hot ground-state species. An increase in thecis-isomer quantum yield uponππ* versusnπ* excitation is observed, which is opposite totrans-azobenzene.