S-1 optical excitation in solution, was studied with femtosecond broadband transient absorption and stimulated Raman spectroscopy, an'/> Photoisomerization pathways and Raman activity of 1,1 '-difluorostilbene
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Photoisomerization pathways and Raman activity of 1,1 '-difluorostilbene

机译：1,1'-dfluorostilbene的光血机化途径和拉曼活动

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The photoisomerization of 1,1'-difluorostilbene, following S-0 -> S-1 optical excitation in solution, was studied with femtosecond broadband transient absorption and stimulated Raman spectroscopy, and by quantum-chemical calculations. In n-hexane, trans-to-cis (t -> c) isomerization starts with Franck-Condon relaxation (tau(1t) = 0.07 ps) followed by nearly barrierless torsion around the ethylenic bond (tau(2t) approximate to 0.3 ps) to a perpendicular conformation P. About 50% of the excited molecules are trapped in P, while others reach the S-1(cis) conformation adiabatically. For the opposite cis-to-trans (c -> t) path, the dynamics in n-hexane (tau(1c) = 0.04 ps, tau(2c) = 0.7 ps) suggest a 5 kJ/mol barrier between the relaxed S-1(cis) and P states. The subsequent P decay with tau(3) = 0.4 ps is followed by much slower ground-state recovery (tau(4) approximate to 3 ps), indicating an intermediate state X. The t -> P and c -> P torsion depend on solvent viscosity and polarity, whereas the P -> X -> S-0 relaxation and residual torsion is viscosity-independent but still polarity-dependent. Photoisomerization yields are derived from the transient absorption data and compared to those from actinometric measurements. Low-frequency oscillations in the transient signal are assigned to nuclei motions. Transient and stationary stimulated Raman spectra are compared to calculations. Early Franck-Condon Raman spectra differ from those of the quasistationary trans or cis S-1 state. The photoisomerization behavior of stilbene and vinyl-substituted derivatives is compared and the general features are discussed. Published by AIP Publishing.
机译：通过飞秒宽带瞬态吸收和刺激的拉曼光谱研究了溶液中S-0 - > S-1光学激发之后的1,1'-二氟硬化酶的光致作用，并通过量子化学计算。在正己烷中，反式到顺式（T - > C）异构化开始于弗兰克 - 康登松弛（TAU（1T）= 0.07 PS），随后围绕烯键（TAU（2T近barrierless扭转）近似到0.3 ps的）垂直构象P.捕获约50％的激发分子被捕获，而其他物质可见地达到S-1（CIS）构象。对于相对的顺式 - 反式（C - > T）路径，N-己烷（TAU（1C）= 0.04 PS，TAU（2C）= 0.7 PS）的动态表明了缓解的S之间的5kJ / mol屏障-1（CIS）和P状态。随后的P衰减与Tau（3）= 0.4 ps之后是较慢的地面恢复（tau（4）近似为3 ps），表示中间状态x。t - > p和c - > p扭转依赖在溶剂粘度和极性上，而P - > X - > S-0弛豫和残余扭转是粘度无关的但仍然依赖性。光血变产率来自瞬态吸收数据，并与来自传感测量测量的相比。瞬态信号中的低频振荡被分配给核动作。将瞬态和静止的刺激拉曼光谱与计算进行比较。早期的Franck-Condon拉曼光谱与Quasistationary Trans或CIS S-1状态不同。比较芪和乙烯基取代衍生物的光硅酸硅酸酯化行为，并讨论了一般特征。通过AIP发布发布。

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