Tuning the Optical Properties of Fluorinated Indolylfulgimides

Abstract

Photochromic fluorinated indolylfulgides have been identified as potential candidates for a wide range of applications including optical switches, photoregulators of biological processes, and optical memory media. In humid environments or biological systems, hydrolytic stability is essential. In an effort to improve hydrolytic stability, a series of indolylfulgimides has been synthesized from a parent trifluoromethyl-substituted indolylfulgide. The nitrogen of the succinimide moiety is linked to either a dimethyl amino or one of seven substituted phenyl groups. The phenyl groups feature substituents with increasing electron-withdrawing ability. The spectral characteristics of each compound have been examined, revealing that the wavelength absorption maxima of each form increases with increasing electron-withdrawing ability of the substituted N-phenyl ring. The quantum yields of the photoreactions have been determined with the N-(phenyl)fulgimide showing a ring closure value of nearly 0.30 in toluene. In addition, the hydrolytic, thermal, and photochemical stabilities of each compound have been measured. The fulgimides exhibit at least a 200-fold enhancement of hydrolytic stability for the Z-form and over a 1000-fold enhancement for the C-form in comparison to the same form of the parent fulgide. The N-(2,3,5,6-tetrafluoro-4-trifluoromethylphenyl)fulgimide can undergo up to 3000 photochemical cycles (coloration followed by bleaching) before losing 20% of its initial absorbance at photostationary state.

All‐Optical Operation Cycle on Molecular Bits with 250‐GHz Clock‐Rate Based on Photochromic Fulgides

“…Provided that the optical pulses applied for write, erase, and readout events are sufficiently short, the response time for toggling between the ground state isomers in molecular switches is governed only by the speed of the photochemical reactions. The optical write-readout-erase-readout operation cycle is based on the photochromic molecular switch trifluoromethylsubstituted indolylfulgide [12][13][14] dissolved in 1,4-dioxane as the information carrier (as seen in Scheme 2). The molecule in the ring-opened form (Z-isomer) is considered as bit-state '0' and the ring-closed C-isomer as bit-state '1'.…”

A comparative study of the fluorescence and photostability of common photoswitches in microstructured optical fibre

“…This thermal degradation may reflect some hydrolysis of CF 3 -fulgide, caused by trace amounts of water in the DMSO. [35] Further photobleaching of CF3-fulgide and its degradation products was observed upon pulsing with the 532 nm excitation source. …”

“…[31][32][33] The trifluorinated indolylfulgide (CF 3 -fulgide), first reported by Yokoyama, [28] has high fatigue resistance, high thermal stability (no thermo-isomerisation) and large separation between ring opening and closing photoisomerisation wavelengths, and as such shows much promise for applications in data storage. [34][35][36] However, 3-indolylfulgides such as CF 3 -fulgide are not known to have a strong fluorescence, which limits their readout capacity. [37] The last example, the diarylalkene 1,2-bis(2,4-dimethyl-5-phenylthiophen-3-yl)-perfluorocyclopentene (DA1) [29,38] has high thermal stability and high photofatigue resistance (>850 cycles) in hexane, demonstrating the potential of diarylalkenes for devices applications.…”

Synthesis and Characterization of Photochromic Copolymers Containing 3-Indolylfulgides/Indolylfulgimides

“…A series of fluorinated indolylfulgimides were synthesized by Lees et al from the precursor fulgide. 35 As shown in Scheme 10, the fulgide was reacted with substituted anilines in the presence of a base, such as of NaH or LDA, to obtain succinamic acid intermediates. Then the succinamic acid intermediates underwent dehydration in acetic anhydride to form the corresponding fulgimides in the overall yield of up to 64%.…”

“…Among photochromic compounds, 3-indolylfulgimides are promising because of their enhanced photochromic properties, such as enhanced thermal stability, increased photochemical stability (fatigue resistance), highly efficient photoreactions, large molar absorption coefficients and hydrolytic stability. 22,27,35,39,81 The photochromism of methyl and trifluoromethyl-3-indolylfulgimides was shown in Scheme 32, where the fulgimides can be converted between the open forms and the closed form reversibly by light.…”