Dobryakov Alexander L, Schriever Daria, Quick Martin, Pérez-Lustres J Luis, Ioffe Ilya N, Kovalenko Sergey A
N. N. Semenov Federal Research Center of Chemical Physics, Russian Academy of Science, Moscow 119991, Russia.
Department of Physics, Free University of Berlin, Berlin 14195, Germany.
J Am Chem Soc. 2024 Nov 27;146(47):32463-32478. doi: 10.1021/jacs.4c09134. Epub 2024 Nov 12.
The photoisomerization rate of -stilbene (tS) and trans-trans-diphenylbutadiene (ttD) is studied in solution and compared to that in jet/gas. Rice-Ramsperger-Kassel-Marcus (RRKM) theory correctly predicts the tS rate in jet, = exp(-/) with = 1398 cm, and = 1.8 ps corresponding to frequency ν = 60 cm of the reactive mode, being the molecular temperature. However, the behavior in solution cannot be explained by the RRKM rate alone. In solution the rate = exp(-/) has a similar form, but depends mainly on solvent temperature and proceeds much faster, = 19 ps, = 1520 cm in -hexane. Moreover, excitation at high excess energy, resulting in molecular temperature = 607 K, affects the rate only slightly, unlike in jet, and contrary to common theoretical models. The experimental results clearly indicate two isomerization paths in solution: via relatively slow intramolecular activation ∼ 1 ps, and by much faster solvent activation = 18 ps due to solute-solvent interactions (collisions). The data in -alkanes confirm previously established power dependence ∼ η on viscosity η, with α = 0.30 for tS, and α = 0.35 for ttD. With being the viscosity barrier, its contribution to can be isolated, giving the intramolecular barrier = ( - α), slightly lower than in jet/gas, probably due to the dispersive/induction interactions in solution.
研究了溶液中反式二苯乙烯（tS）和顺反 - 二苯基丁二烯（ttD）的光异构化速率，并与喷射/气相中的速率进行了比较。赖斯 - 拉姆齐格 - 卡塞尔 - 马库斯（RRKM）理论正确地预测了喷射中tS的速率，即(k = k_0\exp(-\Delta E^/RT))，其中(k_0 = 1398 cm^{-1})，(RT = 1.8 ps)对应于反应模式频率(\nu = 60 cm^{-1})，(T)为分子温度。然而，溶液中的行为不能仅用RRKM速率来解释。在溶液中，速率(k = k_0\exp(-\Delta E^/RT))具有类似的形式，但主要取决于溶剂温度(T_s)，并且进行得更快，在正己烷中(k = 19 ps)，(k_0 = 1520 cm^{-1})。此外，在高过剩能量下激发，导致分子温度(T = 607 K)，与喷射情况不同，且与常见理论模型相反，对速率的影响很小。实验结果清楚地表明溶液中有两条异构化途径：通过相对较慢的分子内活化(\tau_{intra} \sim 1 ps)，以及由于溶质 - 溶剂相互作用（碰撞）导致的快得多的溶剂活化(\tau_{solv} = 18 ps)。正构烷烃中的数据证实了先前确定的粘度(\eta)的幂次依赖性(k \sim \eta^{\alpha})，tS的(\alpha = 0.30)，ttD的(\alpha = 0.35)。通过分离粘度屏障(\Delta E_{\eta})对(k)的贡献，可以得到分子内屏障(\Delta E_{intra} = (\Delta E^* - \alpha\Delta E_{\eta}))，略低于喷射/气相中的值，这可能是由于溶液中的色散/诱导相互作用。
