High Pressure Studies of the Dynamic Solvent Effect in Chemical Reactions in Solution

本课题的目的是了解具有大振幅旋转运动的异构化反应中的“动态溶剂效应”。包括以下两个主要主题：1)分子内电荷转移的异构化动力学溶剂效应；2)非极性溶剂中非极性异构化动力学溶剂效应。高压技术在不改变溶剂势能的情况下，已成为一种连续而广泛地改变溶剂粘度的有力方法。1)带电荷转移异构化的动态溶剂效应：确定了4-（N，N二甲胺）三硝基膦（DMATP）“分子内扭曲电荷转移（TICT）”态形成（kTICT）的速率常数为函数压力。研究了kTICT与溶剂剪切粘度的关系。用溶剂的纵向弛豫（tL）作为溶剂化时间尺度的度量来讨论溶剂化。我们发现反应路径可以理解为从溶剂化控制到分子内振动控制的转变。2)非极性溶剂对非极性异构化的动态溶剂效应：研究的反应体系是2-乙烯基镧(I)和2,2丙烯镧（II）的Si态异构化。测定了从超临界乙烷到压缩液相辛烷的异构化反应的速率常数。i)在高压高粘度条件下，反应受空间扩散控制，表现出非kramers行为。ii)在低粘度、低压条件下，反应由能量扩散控制，其活化能增加，与液相条件下的活化能相同。iii)观察到“克雷默流动率”。iv)与I相比，II的周转平台位于粘度较低的区域。

The purpose of this project is to understand the "dynamic solventeffect" in the isomerizations with large amplitude rotational motion. Following two main subjects are included ; 1) dynamic solvent effect in theisomerization acompanying with intramolecular charge-transfer and 2)dynamic solvent effect in the non-polar isomerization in non-polar solvent. Here, the high pressure technique has been employed as a powerful methodfor chnaging solvent viscosity continuously and widely without modifyingthe solvent potential energy.1) Dynamic solvent effect of the isomerization with charge-transfer : The rate-constant of "twisted intramolecular charge-transfer (TICT)" stateformation (kTICT) for 4-(N,N dimethylamino)trinitrophosphine (DMATP) hasbeen determined as a function pressure. kTICT has been studied as afunction of solvent shear viscosity. Solvation has been discussed byusing longitudinal relaxation of solvent (tL) as a measure of solvationtime scale. We found that the reaction path is understood as the shiftfrom solvation controlled to intramolecular vibration controlled scheme.2) Dynamic solvent effect on non-polar isomerization in non-polarsolvent : The reaction system studied is the Si state isomerization of2-vinylanthracene (I) and 2,2 propenylanthracene (II). The rate constantsof both isomerization reactions have been determined in the series ofalkane solvents frome supercritical ethane to compressed liquid phaseoctane. i) In the high viscosity condition at high pressure where thereaction is controlled by spatial diffusion, the shows non-Kramers behavior. ii) In low viscosity at low pressure where the reaction iscontrolled by energy diffusion, it increases with a same activation energyas in the liqui phase condition. iii) "Kramers turnover" has been observed.iv) The turnover plateau for II locates in the lower viscosity region ascompared with I.