Division of Frontier Materials Science and, Center for Advanced Interdisciplinary Research, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan.
Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa, Japan.
Chemphyschem. 2020 Jul 17;21(14):1524-1530. doi: 10.1002/cphc.202000315. Epub 2020 Jun 22.
The geometrical evolution of the reactant and formation of the photoproduct in the cycloreversion reaction of a diarylethene derivative were probed using time-resolved absorption spectroscopies in the visible to near-infrared and mid-infrared regions. The time-domain vibrational data in the visible region show that the initially formed Franck-Condon state is geometrically relaxed into the minimum in the excited state potential energy surface, concomitantly with the low-frequency coherent vibrations. Theoretical calculations indicate that the nuclear displacement in this coherent vibration is nearly parallel to that in the geometrical relaxation. Time-resolved mid-infrared spectroscopy directly detected the formation of the open-ring isomer with the same time constant as the decrease of the closed-ring isomer in the excited state minimum. This observation reveals that no detectable intermediate, in which the population is accumulated, is present between the excited closed-ring isomer and the open-ring isomer in the ground state.
利用可见近红外和中红外区域的时间分辨吸收光谱研究了二芳基乙烯衍生物的环化重排反应中反应物的几何演变和光产物的形成。可见域的时域振动数据表明，最初形成的 Franck-Condon 态在激发态势能表面上松弛为最小，同时伴随着低频相干振动。理论计算表明，这种相干振动中的核位移几乎与几何弛豫中的核位移平行。时间分辨中红外光谱直接检测到开环异构体的形成，其时间常数与激发态最低的闭环异构体的减少相同。这一观察结果表明，在激发态闭环异构体和基态开环异构体之间不存在可检测的中间态，其中人口积累。
