Self-Assembly of Copper(II) Ion-Mediated Nanotube and Its Supramolecular Chiral Catalytic Behavior

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• 作者：Qingxian Jin ; Li Zhang ; Hai Cao ; Tianyu Wang ; Xuefeng Zhu ; Jian Jiang ; Minghua Liu
• 刊名：Langmuir
• 出版年：2011
• 出版时间：November 15, 2011
• 年：2011
• 卷：27
• 期：22
• 页码：13847-13853
• 全文大小：961K
• 年卷期：v.27,no.22(November 15, 2011)
• ISSN：1520-5827

文摘

Self-assembly of several low-molecular-weight l-glutamic acid-based gelators, which individually formed helical nanotube or nanofiber structures, was investigated in the presence of Cu²⁺ ion. It was found that, when Cu²⁺ was added into the system, the self-assembly manner changed significantly. Only in the case of bolaamphiphilic glutamic acid, N,N鈥?hexadecanedioyl-di-l-glutamic acid (L-HDGA), were the hydrogel formation as well as the nanotube structures maintained. The addition of Cu²⁺ ion caused a transition from monolayer nanotube of L-HDGA to a multilayer nanotube with the thickness of the tubular wall about 10 nm. For the other amphiphiles, the gel was destroyed and nanofiber structures were mainly formed. The formed Cu²⁺-containing nanostructures can function as an asymmetric catalyst for Diels鈥揂lder cycloaddition between cyclopentadiene and aza-chalcone. In comparison with the other Cu²⁺-containing nanostructures, the Cu²⁺-mediated nanotube structure showed not only accelerated reaction rate, but enhanced enantiomeric selectivity. It was suggested that, through the Cu²⁺ mediated nanotube formation, the substrate molecules could be anchored on the nanotube surfaces and produced a stereochemically favored alignment. When adducts reacted with the substrate, both the enantiomeric selectivity and the reaction rate were increased. Since the Cu²⁺-mediated nanotube can be fabricated easily and in large amount, the work opened a new way to perform efficient chiral catalysis through the supramolecular gel.