Photoresponsive dithienylethene-urea-based organogels with “reversed” behavior

Abstract

Dithienylperhydrocyclopentene-bisurea-based low molecular weight gelators are described that function as photoresponsive organogels that show a remarkable gel-to-liquid transition upon irradiation. The two series of derivatives, with and without alkyl spacers between the urea hydrogen bonding groups and the photochromic unit, show different gelation behavior. Upon UV irradiation of the gels, a gel liquified at only 1.4% conversion of the photochromic unit. Transmission electron microscopy (TEM) shows that the gel fibres consist of thin ribbons. Semi-empirical (PM3) calculations indicate that the hydrogen bonding between the open-ring isomer (o) molecules is weak, and that formation of the closed-ring isomer (c) destabilises the hydrogen bonding further. The results indicate that a small amount of the closed-ring isomer will disrupt the intermolecular hydrogen-bonding, leading to disintegration of the gel fibre ribbons and hence reversible liquification.

Photoswitching Behavior of a Cyclohexene‐Bridged versus a Cyclopentene‐Bridged Dithienylethene System

“…They have also been used in supramolecular chemistry 13. Their reversible switching behavior has been studied in solution, in the crystalline state,14 in liquid crystals8, 15 and as gels 16…”

Light‐Triggered Self‐Assembly of a Spiropyran‐Functionalized Dendron into Nano‐/Micrometer‐Sized Particles and Photoresponsive Organogel with Switchable Fluorescence

“…[17][18][19][20][21][22][23][24][25][26][27][28][29][30] For instance, photochromic organogels featuring bisthienylethene with intriguing optical properties have been studied. [31][32][33] Some SP-functionalized macromolecular gels have also been reported. [34] However, to the best of our knowledge, LMWGs with the SP moiety still remain rare.…”

Solvation effects with a photoresponsive two-component 12-hydroxystearic acid-azobenzene additive organogel

“…Besides the rational design of new potent organogelator candidates, some LMOGs are also sensitive to other stimuli such as photochemical [14][15][16][17][18][19][20][21], chemical [22], enzymatic [23,24], and mechanochemical [25,26] stimuli.…”