Ring Closure Reaction Pathway of a Diarylethene in Solution Using Femtosecond Time‐resolved Fluorescence Spectra

Abstract

Photochromic ring closure reaction dynamics of 1,2-bis(2-methylbenzo[b]thiophene-3-yl)hexafluoro cyclopentene is investigated by means of time-resolved fluorescence spectra. Compared with a single wavelength probe, direct measurement of the emission spectra during the reaction provides unambiguous and straightforward picture for the ring closure reaction pathway. We observe two different emission bands in the fluorescence of the open ring isomer. From the global analysis for the spectra, we obtain <1 ps time constant for the ring closure reaction in polar solvent. Moreover, the ring closure reaction of the compound takes place entirely on the ultrafast timescale. The unreactive parallel conformer decays to the ground state by 150 ps time constant.

Half-Broadband Two-dimensional Electronic Spectroscopy with Active Noise Reduction

“…A 600 mOD solution (1 mm cell) of the closed form of DAE in CHX was obtained by continuous irradiation of the UV absorbing open form with a 285 nm LED (Thorlabs), at 5 mW for 2 hours. HB2DES spectra were collected without flowing as no differences in the absorption spectrum before and after the measurement were observed, consistent with the low quantum yield of ring opening [63,64]. The sample was excited by pulses centred at 16900 cm −1 with ∼0.8 µJ energy per pulse pair and probed by the WLC spanning 13000-24000 cm −1 .…”

Half-Broadband Two-dimensional Electronic Spectroscopy with Active Noise Reduction

“…A 600 mOD solution (1 mm cell) of the visible absorbing form of DAE in CHX was obtained by continuous irradiation of the open (UV absorbing) form with a 275 nm LED (Thorlabs), at 5 mW for 2 hours. HB2DES spectra were collected in a static 1 mm cell as no differences in the absorption spectrum before and after the 2DES measurement were observed, consistent with the low quantum yield of ring opening [63,64]. The sample was excited by NOPA pulses (orange shaded area in fig.…”

Cyclization Dynamics and Competitive Processes of Photochromic Perfluorocyclopentene Dithienylethylene in Solution

“…[16,17] To overpass such limitation some researchers focused their efforts on exploring purposed-designed synthetic approach [18][19][20][21] or specific excited-state reactivity. [22,23] Indeed, the rationalization of complex excited state mechanisms are highly desired to still improve photochromic performances and so considerable investigations have been devoted worldwide to explore the excited state topologies of DTEs (or DAEs) via advanced optical spectroscopies [24][25][26][27] and/or computational chemistry. [28][29][30] In this perspective, our group has actively investigated the spectrokinetic features on the series of bridged DAEs, [31] bridged DTEs [29,32,33] or DTEs dedicated to supramolecular chemistry [34] using ultrafast spectroscopies combined with (TD)-DFT calculations.…”