Diarylethene-based xerogels: the fabrication of more entangled networks driven by isomerization and acidofluorochromism

Abstract

Fully-conjugated styrylbenzoxazoles and styrylbenzothiazoles of BOAF24, BOACl24, BOACl35, BOABr24, BOABr35, BTAF24, BTACl24 and BTABr24 without traditional gelation groups could form organogels. It was found that introduction of chlorine atoms in the 2,4-positions of the phenyl group would improve gelation abilities, and benzothiazole derivatives exhibited better gelation abilities than benzoxazoles with a similar π-skeleton due to better π-electron delocalization. Interestingly, the organogel of BTACl24 could change into solution by UV light due to trans-cis isomerization, which could also induce morphological changes in xerogels. The smooth organogel nanofibers stretched out lots of thin 'arms' to hold together or to catch other nanofibers upon UV irradiation, so more entangled networks were generated. Moreover, TFA (trifluoroacetic acid) could induce a gel-sol transformation on account of the protonation of the benzoxazole or benzothiazole unit, accompanied by emission quenching. BTACl24 exhibited higher performance than BOACl24 in the detection of TFA because of its strong basicity. The decay time and the detection limit of BTACl24 in xerogel-based film towards TFA vapor were of 0.7 s and 0.3 ppm, respectively. Therefore, organogelation of non-traditional organogelators is a powerful approach to the fabrication of multi-stimuli-responsive soft materials, and provides a new method to generate more entangled 3D networks through photochemical reactions in xerogels.

Positive/Negative Phototropism: Controllable Molecular Actuators with Different Bending Behavior

“…The syntheses of BOAF4, BOAF24, and BTAF24 were reported previously. 41,48 BTAF4 was synthesized according to the reported procedure. 41 The synthetic route and characterization data were shown in the Supporting Information.…”

“…To further research the positive and negative phototropism behavior of crystals under UV irradiation, BOAF24 was designed and synthesized for comparison with BOAF4. 48 BOAF24 formed block, ribbon-like, and rod-like crystals in petroleum ether/CH 2 Cl 2 (v/v = 3/1). The long block irregular crystal of BOAF24 could swing upon UV irradiation, and small pieces jumped away from the body.…”

Photomechanical effects of acidochromic diarylethene derivatives

“…Knoevenagel缩合反应生成BO1N4F和BT1N4F, 产率 分别为70%和67% [34] . 粗产物经柱层析提纯, 利用核磁 共振氢谱、碳谱、红外光谱和高分辨质谱对目标分子 的结构进行表征.…”

“…可见, 阻断发光基团间的强π-π相互作用是设计 高效固态发光材料的有效策略. 在前期工作中, 本课题 组利用小分子有机凝胶剂的胶凝化构筑了基于菲并咪 唑 [30] 、苯并噻唑 [31] 、嘧啶取代的β-亚胺酮二氟化 硼 [32] 、苯乙烯基喹喔啉 [33] 、苯乙烯基苯并 唑衍生 物 [34] [47] 、跳跃和爆裂 [48,49] 等运动的驱动力.…”

Synthesis of a Stable Benzoxazole Gel from an Imine Gel for Adsorption and Catalysis

“…High stability is important in enhancing the performance of gel catalyst recycling. Stable polymer gels with acid- and alkali-resistant properties as adsorbents have aroused the interest of scientists. ,− On the other hand, supramolecular gels assembled from small molecules via hydrogen bonding, π–π stacking, van der Waals interactions, and other supramolecular weak interactions have been developed as adsorbents and catalysts in recent years. − Supramolecular gels show greater structural diversity and easier incorporation of functional groups than polymer gels. They have potential for the adsorption of pollutants because small molecules or metal ions can rapidly diffuse within them easily.…”