Wezenberg Sander J, Croisetu Christelle M, Stuart Marc C A, Feringa Ben L
Stratingh Institute for Chemistry , University of Groningen , Nijenborgh 4 , 9747 AG , Groningen , The Netherlands . Email:
Groningen Biomolecular Sciences and Biotechnology Institute , University of Groningen , Nijenborgh 7 , 9747 AG , Groningen , The Netherlands.
Chem Sci. 2016 Jul 1;7(7):4341-4346. doi: 10.1039/c6sc00659k. Epub 2016 Mar 22.
A new type of low-molecular-weight gelator (LMWG), overcrowded alkene-based bis-ureas, can be switched effectively between and isomers using light as demonstrated by H NMR and UV-Vis spectroscopy. Gelation studies reveal that one of the synthesized compounds forms stable gels in aromatic hydrocarbon solvents down to a critical concentration of 0.4 mg mL. Transmission electron microscopy (TEM) shows that this gel consists of an entangled fibrous network. For the isomer of this LMWG intermolecular urea hydrogen bonding is observed in the solid state, whereas density functional theory (DFT) geometry optimization of the isomer indicates the possible formation of an intramolecular hydrogen bond. Irradiation of the gel triggers -to- isomerization and consequently, a gel-sol phase transition. This process can be fully reversed by altering the irradiation wavelength.
一种新型的低分子量凝胶剂（LMWG），即过度拥挤的基于烯烃的双脲，如¹H NMR和紫外可见光谱所示，可通过光照在顺式和反式异构体之间有效切换。凝胶化研究表明，其中一种合成化合物在芳烃溶剂中形成稳定凝胶，临界浓度低至0.4 mg/mL。透射电子显微镜（TEM）显示，这种凝胶由缠结的纤维网络组成。对于这种LMWG的反式异构体，在固态下观察到分子间脲氢键，而顺式异构体的密度泛函理论（DFT）几何优化表明可能形成分子内氢键。凝胶的辐照引发反式到顺式异构化，从而导致凝胶-溶胶相变。通过改变辐照波长，这个过程可以完全逆转。
