Ring Closure Reaction Dynamics of Diarylethene Derivatives in Solution

Abstract

Photochromic ring closure reaction dynamics of 1,2-bis(2-methylbenzo[b]thiophen-3-yl)hexafluoro cyclopentene and its derivatives in solution has been studied by femtosecond time-resolved fluorescence. Time-resolved spontaneous fluorescence of the open isomer reveals a fast component of around 1 ps and a slow component on the order of 100 ps. Fluorescence time profiles, reaction quantum yields, and relative populations of the parallel (C(s) symmetry) and antiparallel (C(2) symmetry) conformations indicate that both time components are attributable mostly to the C(2) conformer that undergoes the ring closure reaction. The fast component is assigned to the direct ring closure reaction, and the slow component is assigned to the reaction through conformation change. Time constants of the slow component for the derivatives are inversely proportional to the reaction quantum yields, suggesting that the rate of the conformational dynamics is comparable to the rate of other population relaxation processes. The relative amplitude and exact time constant of the fast component depend on the detection wavelength displaying a higher relative amplitude with shorter time constant at longer wavelengths. The results allow us to propose a conformational inhomogeneity model, in which a broad distribution of conformations of the open isomers in the ground state is projected into two minima in the excited electronic potential surface to lead to the slow and the fast reaction pathways.

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

“…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 .…”

Picosecond cyclization reaction dynamics of furan-based diarylethene with thiosemicarbazone side-chain groups

“…The relaxation time profile was fitted by exponential decay function with time constant, t relax = 68 ± 15 ps, in line with the proposed reaction model [10] with similar dynamics compared to other DAEs [11,12]. Thus, we found that the upper boundary of the rise time is 1.1 ps for photoinduced cyclization reaction of CF5-TSC.…”

“…Taking into account that the determined cyclization time of СF5-TSC is close to all CF5-based DAEs studied by pump-probe spectroscopy [10,12,16] and the relaxation profile has a similar shape [9,11,13], we conclude that the exchange of thiophene against furan apparently has no impact on the ring-closing dynamics of the resulting DAE. Hence, for an application of СF5-based DAE in a combination with gold electrodes, the use of furan-based DAE will be a technical benefit, since oxygen atoms are chemically inert towards gold when compared with sulfur [25].…”