Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan.
Phys Chem Chem Phys. 2011 Apr 7;13(13):5546-55. doi: 10.1039/c0cp01588a. Epub 2011 Feb 28.
Have you ever hoped to observe transition states? Chemists have long desired to monitor the deformation of molecular structures via transition states to understand the mechanisms of complicated reactions. Detailed knowledge of transition states helps find strategies to develop novel reaction schemes for introducing new functionalities to chemicals. Molecular structural changes via transition states can be observed by real-time vibrational spectroscopy using sub-5 fs laser pulses. In this paper, I report the direct observation of time-dependent frequency shifts of relevant molecular vibrational modes, which allowed for the clear visualization of ultrafast structural changes in molecules during bond breaking and bond reformation steps. Various mechanisms for photochemical reactions were clarified using sub-5 fs laser pulses. Moreover, a non-thermal vibrational excitation method for efficiently driving chemical reactions in the electronic ground state in solution with the use of broadband visible sub-5 fs laser pulses has been developed. The respective chemical reaction processes were directly observed, including transition states during not only "photochemical" but also "thermal" reactions. Time-resolved spectroscopy with a time resolution of a few femtoseconds enables observation of real-time vibrational amplitudes of complicated molecules and opens up new ways for clarifying reaction mechanisms and developing new chemical transformations.
你是否曾希望观察过渡态？长期以来，化学家一直希望通过过渡态来监测分子结构的变形，以了解复杂反应的机理。对过渡态的详细了解有助于找到引入新功能的新反应方案的策略。通过使用亚 5fs 激光脉冲的实时振动光谱，可以观察到通过过渡态的分子结构变化。在本文中，我报告了相关分子振动模式的时变频率位移的直接观察，这使得在键断裂和键形成步骤期间分子中超快结构变化的清晰可视化成为可能。使用亚 5fs 激光脉冲阐明了各种光化学反应机制。此外，还开发了一种非热振动激发方法，可在溶液中使用宽带可见亚 5fs 激光脉冲有效地驱动电子基态中的化学反应。直接观察了各自的化学反应过程，包括“光化学”和“热”反应过程中的过渡态。具有几个飞秒时间分辨率的时间分辨光谱学能够观察复杂分子的实时振动幅度，并为阐明反应机理和开发新的化学转化开辟了新途径。
