Vibrational coherence and quantum yield of retinal-chromophore-inspired molecular switches
Vibrational coherence and quantum yield of retinal-chromophore-inspired molecular switches
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DOI：
10.1039/c9fd00062c
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发表时间：
2020-01-01
影响因子：
3.4
通讯作者：
Leonard, Jeremie
中科院分区：
文献类型：
--
作者：
Gueye, Moussa;Paolino, Marco;Leonard, Jeremie
紫外 - 可见瞬态吸收（TA）光谱用于对一组基于相同的类视黄醛、茚满亚基吡咯啉鎓（IP）分子框架的六种生色团的超快C═C双键光异构化动力学以及每种异构体的量子产率进行系统研究。所有化合物都经历亚皮秒级的光异构化，并且可归类于两种光异构化情形。情形I对应于那些通过锥形交叉点显示出振动相干反应运动特征且具有不同程度振动相干性的化合物。对于其他化合物观察到性质不同的TA特征，因此推测它们遵循情形II，即介于情形I和热平衡的完全随机光反应之间的一种中间状态。值得注意的是，观察到光异构化情形与基态平衡几何结构的平面性计算偏差相关，这反映了光激发后将会释放的扭转应变。最平面的化合物——即那些C═C双键预扭转小于10度的化合物——遵循情形II，而遵循情形I的化合物具有更大的预扭转。预扭转程度最大（>15度）的化合物在S₀光产物中显示出由反应诱导的低频振动波包的明显振荡特征，并被归属于反应坐标的扭转模式，从而模拟了视紫红质蛋白的振动相干光异构化动力学。重要的是，对所有光异构化量子产率的系统比较并未揭示出与诸如激发态寿命、振动相干性、吸收波长或预扭转程度等可观测性质的任何相关性。
UV-Vis transient absorption (TA) spectroscopy is used to carry out a systematic investigation of the ultrafast C?C double photoisomerization dynamics and quantum yield of each isomer of a set of six chromophores based on the same retinal-inspired, indanylidene pyrrolinium (IP) molecular framework. All compounds undergo a sub-picosecond photoisomerization, and can be categorized within two photoisomerization scenarios. Scenario I corresponds to compounds which display the signatures of a vibrationally coherent reactive motion through the conical intersection, with different degrees of vibrational coherence. Qualitatively distinct TA signatures are observed for other compounds which are therefore proposed to obey scenario II, referring to an intermediate regime between scenario I and a thermally-equilibrated, fully stochastic photoreaction. Remarkably, the photoisomerization scenario is observed to correlate with the computed distortion from planarity of the ground state equilibrium geometry, reflecting the torsional strain that would be released after photoexcitation. The most planar compounds - i.e. those having a C?C double bond pre-twist of less than 10 degrees - obey scenario II, while compounds obeying scenario I have larger pre-twists. The most pre-twisted compounds (>15 degrees) show pronounced oscillatory signatures of a reaction-induced, low-frequency vibrational wavepacket observed in the S-0 photoproduct and assigned to the torsion mode of the reaction coordinate, thus mimicking the vibrationally coherent photoisomerization dynamics of the rhodopsin protein. Importantly, the systematic comparison of all photoisomerization quantum yields does however not reveal any correlation with observables such as excited state life time, vibrational coherence, absorption wavelengths or degree of pre-twisting.