Femtosecond Dynamics of the Ring Closing Process of Diarylethene: A Case Study of Electrocyclic Reactions in Photochromic Single Crystals

Abstract

The cyclization reaction of the photochromic diarylethene derivative 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene was studied in its single crystal phase with femtosecond transient absorption spectroscopy. The transient absorption measurements were performed with a robust acquisition scheme that explicitly exploits the photoreversibility of the molecular system and monitors the reversibility conditions. The crystalline system demonstrated 3 × 10(4) repeatable cycles before significant degradation was observed. Immediately following photoexcitation, the excited state absorption associated with the open-ring conformation undergoes a large spectral shift with a time constant of approximately 200 fs. Following this evolution on the excited state potential energy surface, the ring closure occurs with a time constant of 5.3 ps, which is significantly slower than previously reported measurements for similar derivatives in the solution phase. Time resolved electron diffraction studies were used to further demonstrate the assignment of the transient absorption dynamics to the ring closing reaction. The mechanistic details of the ring closing are discussed in the context of prior computational work along with a vibrational mode analysis using density functional theory to give some insight into the primary motions involved in the ring closing reaction.

Light penetration-coupled photoisomerization modeling for photodeformation of diarylethene single crystal: upscaling isomerization to macroscopic deformation

“…4a) irradiated by a UV laser pulse. The time constant (0.59 ps) of the theoretical model is within in a few picoseconds of experimental data 22, 25, 26 for various diarylethene derivatives, and the model simulated reliable population transition processes for the cyclization.

Figure 4( a ) Population of the ground state of the closed ring isomer under UV pulse laser irradiation (cyclization). ( b ) Population of the first excited state of the closed ring isomer according to the temperature under vis pulse laser irradiation (cycloreversion).

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“…The photo-switching properties are obtained from first principle calculations (time-dependent density functional theory (TD-DFT), density functional theory (DFT), and complete active space self-consistent-field (CASSCF) calculations). Experimental comparisons 4, 22–26 are given to confirm the reliability of our modeling.…”

“…The reliability of our statistical photoisomerization model is validated by comparison with experimental results (transient-absorption spectroscopy) 22–26 . To identify the pulsed laser irradiation conditions from the experiment, the starting point of the population transition is set to the excited state of initial isomer in the model.…”

“…In the following section, the time-evolutional population profile of each state is calculated based on the statistical photoisomerization model, and validated by comparing with the transient-absorption experiment 22–26 .…”

Femtosecond Electron Diffraction Study of the Cyclization Reaction in Crystalline Diarylethene

“…In order to characterize the timescales involved and to optimize the excitation conditions for the electron diffraction experiment, we have recently performed femtosecond transient absorption studies of the cyclization reaction in this diarylethene derivative in its crystalline phase [2]. After demonstrating the possibility to achieve 3x10 4 repeatable ring closing and opening cycles, the dynamics of interest were fully resolved using a robust acquisition scheme which directly exploits this photoreversibility.…”