Laboratoire des IMRCP, Université de Toulouse, CNRS UMR 5623, Université Toulouse III - Paul Sabatier, 118 Rte de Narbonne, 31062 Toulouse cedex 9, France.
Institut des Molécules et Matériaux du Mans (IMMM), UMR CNRS 6283, Equipe Polymères, Colloïdes, Interfaces, Le Mans Université, Avenue Olivier Messiaën, 72085 Le Mans Cedex 9, France.
J Colloid Interface Sci. 2023 Jan;629(Pt A):670-684. doi: 10.1016/j.jcis.2022.08.191. Epub 2022 Sep 5.
Switchable assemblies relevant for bio-applications may be accessed from water-soluble tetra-ortho-substituted azobenzenes that reversibly self-assemble and form complexes with β-cyclodextrin under visible light.
Two azobenzenes bearing either four fluorines or two chlorines and two fluorines in the ortho positions were synthesised with short poly(ethylene oxide) tails for water solubility. Photophysical properties were determined by UV-vis and H NMR spectroscopies, complexation with β-cyclodextrin was assessed by H NMR spectroscopy, and self-assembly in water was investigated by static and dynamic light scattering.
Both molecules underwent trans-cis isomerization at 530 nm and cis-trans isomerization at 415 nm, with the cis forms exhibiting thermal half-lives > 300 days at room temperature. Both molecules formed inclusion complexes with β-cyclodextrin in water, with cis-4F-AZO-PEO binding 3-fold stronger than trans, and 2Cl2F-AZO-PEO binding significantly weaker. Self-assembly of pure 2Cl2F-AZO-PEO in water showed an open association process regardless of configuration, while 4F-AZO-PEO showed an open association process for cis (N increasing from 30 to 1000) but a closed association process for trans (N stable at ∼ 170). Aqueous solutions of 2Cl2F-AZO-PEO showed cloud points close to 45 °C, while the 4F-AZO-PEO isomers presented well-separated cloud points allowing reversible and all-visible transition between clear and turbid states at room temperature.
可切换的组装体与生物应用相关，可以从水溶性的四邻位取代的偶氮苯获得，这些偶氮苯在可见光下可逆地自组装并与β-环糊精形成配合物。
合成了两个带有四个氟原子或两个氯原子和两个氟原子的偶氮苯，它们在邻位带有短的聚（氧化乙烯）尾以增加水溶性。通过紫外可见光谱和 H NMR 光谱测定了光物理性质，通过 H NMR 光谱评估了与β-环糊精的络合，通过静态和动态光散射研究了在水中的自组装。
两个分子在 530nm 处发生反式顺式异构化，在 415nm 处发生顺式反式异构化，顺式异构体在室温下的热半衰期>300 天。两个分子在水中均与β-环糊精形成包合物，顺式 4F-AZO-PEO 的结合力比反式强 3 倍，而 2Cl2F-AZO-PEO 的结合力明显较弱。纯 2Cl2F-AZO-PEO 在水中的自组装显示出开放的缔合过程，无论构型如何，而 4F-AZO-PEO 显示出顺式的开放缔合过程（N 从 30 增加到 1000），但反式的封闭缔合过程（N 稳定在~170）。2Cl2F-AZO-PEO 的水溶液的浊点接近 45°C，而 4F-AZO-PEO 异构体呈现出明显分离的浊点，允许在室温下在透明和混浊状态之间进行可逆和全可见的转变。
