Ibrahim Mohamed I A, Pickaert Guillaume, Stefan Loïc, Jamart-Grégoire Brigitte, Bodiguel Jacques, Averlant-Petit Marie-Christine
Laboratoire de Chimie-Physique Macromoléculaire (LCPM), UMR 7375, CNRS, Université de Lorraine Nancy France
Laboratory of Marine Chemistry, Marine Environment Division, National Institute of Oceanography and Fisheries, NIOF Egypt
RSC Adv. 2020 Dec 7;10(71):43859-43869. doi: 10.1039/d0ra07775e. eCollection 2020 Nov 27.
Molecular self-assembly is a fascinating process which has become an area of great interest in supramolecular chemistry, as it leads in certain cases to molecular gels. Organogels formulated from low molecular weight compounds (LMWOGs) have attracted much interest in the past decades due to their applications as new soft materials. Herein, we report on the ability of the cyclic pseudopeptide cyclo-[-(d-Phe-azaPhe-Ala)-] (2) to self-assemble in some aromatic solvents and to form organogels driven by non-covalent forces, mainly hydrogen bonding and π-stacking interactions. Comprehensive FTIR and NMR studies emphasized that this cyclic aza-peptide adopts a β-turn conformation at low concentration in toluene, while an equilibrium between the monomeric states (intramolecular forces) and the supramolecular structures (intra- and intermolecular forces) is established at high concentration (gel state). Rheological investigations of the organogels highlight the dependence of their stiffness (up to ∼4 kPa) and sol/gel transition temperatures (up to 100 °C) as a function of the solvent and concentration of gelator used. The formulation of fibrous structures confirmed the phenomenon of self-assembly. Finally, we found that cyclo-[-(d-Phe-azaPhe-Ala)-] is an effective organogelator for application in phase selective gelation (PSG) of organic solvents from aqueous/organic mixtures with recovery percents up to 96%.
分子自组装是一个引人入胜的过程，在超分子化学领域已成为一个备受关注的领域，因为在某些情况下它会形成分子凝胶。由低分子量化合物（LMWOGs）配制的有机凝胶在过去几十年中因其作为新型软材料的应用而备受关注。在此，我们报道了环状假肽环-[-(d-苯丙氨酸-氮杂苯丙氨酸-丙氨酸)-]（2）在某些芳香族溶剂中自组装并通过非共价力（主要是氢键和π-堆积相互作用）形成有机凝胶的能力。全面的傅里叶变换红外光谱（FTIR）和核磁共振（NMR）研究强调，这种环状氮杂肽在甲苯中低浓度时采用β-转角构象，而在高浓度（凝胶态）时单体状态（分子内力）和超分子结构（分子内和分子间力）之间建立了平衡。对有机凝胶的流变学研究突出了其刚度（高达约4 kPa）和溶胶/凝胶转变温度（高达100℃）随所用溶剂和凝胶剂浓度的变化。纤维状结构的形成证实了自组装现象。最后，我们发现环-[-(d-苯丙氨酸-氮杂苯丙氨酸-丙氨酸)-]是一种有效的有机凝胶剂，可用于从水/有机混合物中对有机溶剂进行相选择性凝胶化（PSG），回收率高达96%。
