美国堪萨斯州立大学Rolles, Daniel团队报道了四环分子光切换的超快电子弛豫路径。相关研究成果于2024年2月2日发表在《自然—化学》。

光诱导的降冰片二烯分子异构体和四环烷之间的超快转换可以可逆地储存和释放大量的化学能。先前的工作在紫外线激发下观察到两种异构体中的超快分子动力学特征，但无法在实验上完全遵循电子弛豫回到基态。

该文中，研究人员使用时间分辨气相极紫外光电子能谱和非绝热分子动力学模拟研究了四环烷在紫外线（201纳米）激发后的电子弛豫。确定了两种相互竞争的途径，通过这两种途径，电子激发的四环烷分子弛豫到电子基态。

快速路径（<100飞秒）的区别在于与价电子态的有效耦合，而慢速路径涉及跨越里德堡态的初始运动，需要几百飞秒。尽管在不同的时间尺度上，这两种途径都促进了两种异构体之间的相互转化，研究预测降冰片二烯/四环烷产物在返回电子基态后的支化比约为3:2。

附：英文原文

Title: Ultrafast electronic relaxation pathways of the molecular photoswitch quadricyclane

Author: Borne, Kurtis D., Cooper, Joseph C., Ashfold, Michael N. R., Bachmann, Julien, Bhattacharyya, Surjendu, Boll, Rebecca, Bonanomi, Matteo, Bosch, Michael, Callegari, Carlo, Centurion, Martin, Coreno, Marcello, Curchod, Basile F. E., Danailov, Miltcho B., Demidovich, Alexander, Di Fraia, Michele, Erk, Benjamin, Faccial, Davide, Feifel, Raimund, Forbes, Ruaridh J. G., Hansen, Christopher S., Holland, David M. P., Ingle, Rebecca A., Lindh, Roland, Ma, Lingyu, McGhee, Henry G., Muvva, Sri Bhavya, Nunes, Joao Pedro Figueira, Odate, Asami, Pathak, Shashank, Plekan, Oksana, Prince, Kevin C., Rebernik, Primoz, Rouze, Arnaud, Rudenko, Artem, Simoncig, Alberto, Squibb, Richard J., Venkatachalam, Anbu Selvam, Vozzi, Caterina, Weber, Peter M., Kirrander, Adam, Rolles, Daniel

Issue&Volume: 2024-02-02

Abstract: The light-induced ultrafast switching between molecular isomers norbornadiene and quadricyclane can reversibly store and release a substantial amount of chemical energy. Prior work observed signatures of ultrafast molecular dynamics in both isomers upon ultraviolet excitation but could not follow the electronic relaxation all the way back to the ground state experimentally. Here we study the electronic relaxation of quadricyclane after exciting in the ultraviolet (201nanometres) using time-resolved gas-phase extreme ultraviolet photoelectron spectroscopy combined with non-adiabatic molecular dynamics simulations. We identify two competing pathways by which electronically excited quadricyclane molecules relax to the electronic ground state. The fast pathway (<100femtoseconds) is distinguished by effective coupling to valence electronic states, while the slow pathway involves initial motions across Rydberg states and takes several hundred femtoseconds. Both pathways facilitate interconversion between the two isomers, albeit on different timescales, and we predict that the branching ratio of norbornadiene/quadricyclane products immediately after returning to the electronic ground state is approximately 3:2.

DOI: 10.1038/s41557-023-01420-w

Source: https://www.nature.com/articles/s41557-023-01420-w