Cis‐stilbene isomerization: Temperature dependence and the role of mechanical friction
Cis‐stilbene isomerization: Temperature dependence and the role of mechanical friction
复制标题
顺式二苯乙烯异构化：温度依赖性和机械摩擦的作用
DOI：
10.1063/1.464672
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发表时间：
1993
影响因子：
4.4
通讯作者：
G. Fleming
中科院分区：
文献类型：
--
作者：
D. Todd;G. Fleming
在很大的温度范围内，测定了顺式二苯乙烯在多种溶剂中的荧光衰减时间。在正构烷烃中的等粘度阿累尼乌斯曲线得到的活化能为386±29 cm−1。我们将这一结果解释为在非极性溶剂中顺式-反式二苯乙烯势垒的上限。在小醇中的等粘度曲线是非线性的，这表明在这种溶剂类型中的复杂行为。当绘制成链长n的函数图时，正构醇和正构烷烃中的激发态衰减时间彼此关联很好。从这个图中我们推断，宏观粘度不能很好地衡量异构化物种在更换溶剂时感受到的摩擦，并且n-≥5的正构烷烃和正构醇之间的势能面没有实质性的变化。在异丙醇中测得的第490,475,453和440 nm发射的衰减时间相差不超过90fs，表明在激发态寿命期间几乎没有或没有光谱演化。一个矮人..。
The fluorescence decay time of cis‐stilbene has been measured in a variety of solvents over a large temperature range. An isoviscosity Arrhenius plot in n‐alkanes yields an activation energy of 386±29 cm−1. We interpret this result as an upper limit for the cis‐stilbene to trans‐stilbene barrier in nonpolar solvents. Isoviscosity plots in small alcohols are nonlinear, indicating complicated behavior in this solvent type. The excited state decay times in n‐alcohols and n‐alkane solvents correlate well with each other when plotted as a function of chain length, n. We infer from this plot that macroscopic viscosity is a poor measure of the friction felt by the isomerizing species when changing solvent, and that the potential energy surface is not substantially altered between n‐alkanes and n‐alcohols with n≥5. Decay times measured in 2‐propanol at 490, 475, 453, and 440 nm emission differ by no more than 90 fs, indicating that there is little or no spectral evolution during the excited state lifetime. A shor...