Tuning of Optical Properties and Thermal Cycloreversion Reactivity of Photochromic Diarylbenzene by Introducing Electron-Donating Substituents

Abstract

Thermally reversible photochromic compounds having excellent physicochemical properties can be exploited for many practical applications, such as ophthalmic lenses, real-time holography, and super-resolution microscopy. In this study, we have designed and synthesized novel 1,2diarylbenzene derivatives bearing various electron-donating substituents at p-position of the 2 phenyl ring to tune the optical and thermal properties for the practical applications. Introduction of the electron-donating groups resulted in the red-shift of the absorption spectra, increase in the absorption coefficients of the open-ring isomers, and deceleration of the thermal cycloreversion of the closed-ring isomers. Theoretical analysis based on Hammett's substituent constant and density functional theory revealed that the rate of thermal cycloreversion became lower in proportion to the electron-donating ability of the substituent. The novel 1,2-diarylbenzene derivatives synthesized here could undergo photocyclization upon irradiation with UV-A light and fast thermal cycloreversion with a half-life of a few hundred milliseconds to seconds.

Broadening the Horizon of the Bell–Evans–Polanyi Principle towards Optically Triggered Structure Planarization

“…Details of the synthetic route and characterization are presented in the Supporting Information. As shown in single-crystal X-ray diffraction analyses ( Figure 2; Supporting Information, Table S1), [37] all the PDBAs exhibit bent dibenzo[b,f]azepine structures with bay angles V s1 (defined by the angle between the C(6)-C(7)-C(9) plane and the C(1)-C(6)-C(14) plane) of 21-288 8 and V s2 (defined by the angle between the C(1)-N-C (14) plane and the C(1)-C(6)-C (14) plane) of 47-578 8.M oreover,t he bending angle V a (angle between the C(1)-C(3)-C(4) plane and the C(14)-C(12)-C(11)) of PDBA was recorded as 1268 8,while that of DBA was substantially greater at 1448 8,a nd the angle V b (the angle between the C(7)-C(8)-N plane and the line along N-C(15)) was 1078 8 and 1348 8 for PDBA and DBA,r espectively.T his difference can be attributed to the steric interactions between the N-substituted phenyl group and the dibenzazepine core. When the substituent was varied from an electron-donating group (-OMe) to an electron-withdrawing group ( (Figure 2), presumably due to charge transfer from the N-phenyl nitrogen to the para substituent.…”

A Molecular‐Switch‐Embedded Organic Photodiode for Capturing Images against Strong Backlight

“…Instead, as shown in Figure S3a, Supporting Information, another similar diarylethene derivative, 1,2-bis(2-methyl-5-(4-cyanobiphenyl)-3-thienyl)hexafluorocyclopentene (DAE), was designed by replacing the ethene moiety with tetrafluorobenzene and hexafluorocyclopentene to intentionally slow down the cycloreversion, while maintaining the same aryl moiety. [37][38][39][40] The absorption spectra of the DAE solution were measured after illumination with white light (AM1.5G spectral shape) of various intensities, from low to high. To ensure consistency with the OPD measurements, 1 s of illumination was applied to each measurement, which is a sufficient time for reaching a photocyclization-photocycloreversion equilibrium.…”

Broadening the Horizon of the Bell–Evans–Polanyi Principle towards Optically Triggered Structure Planarization

“…These lead to the conclusion that a decrease in the reaction barrier should increase the reaction exothermicity. While the B‐E‐P principle has been applied to a number of reactions involving bond rearrangement, [9–14] the fundamental issue of whether the reaction parameters, e.g., transition‐state structure and reactive frequency, meet the criteria is often overlooked.…”

“…where E 0 is the intercept, and a is avalue characteristic of the transition state along the reaction coordinate,w hich should be in the range of 0 a < 1. These lead to the conclusion that adecrease in the reaction barrier should increase the reaction exothermicity.While the B-E-P principle has been applied to anumber of reactions involving bond rearrangement, [9][10][11][12][13][14] the fundamental issue of whether the reaction parameters,e .g., transition-state structure and reactive frequency, meet the criteria is often overlooked. In yet another instance,u pon excitation, changes in the electron density distribution are induced, where structure relaxation becomes au biquitous phenomenon.…”