Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
J Phys Chem B. 2020 Sep 17;124(37):8179-8187. doi: 10.1021/acs.jpcb.0c05545. Epub 2020 Aug 18.
The coordination effects between chiral Schiff bases and metal ions can provide an effective strategy for fabricating chiral supramolecular self-assemblies. We studied the supramolecular self-assembly of the amphiphilic Schiff base enantiomer, 2-hydroxy-1-naphthylmethylamino-,'-bis(octadecyl)-l/d-glutamic diamide (l/dGJ), at the air/water interfaces by using in situ second harmonic generation linear dichroism (SHG-LD) technique combined with UV-vis spectroscopy and atom force microscopy. lGJ and dGJ monolayers can form mirror-image structures of each other at different interfaces, which can be mediated by metal ions. When Mg and Zn ions were added into the subphases, the l/dGJ monolayers self-assembled into a nanofiber-like structure and showed significant chirality similar to that at the pure water interface. However, when Cu ions were added into the subphase, the chirality of the l/dGJ monolayer was destroyed because of the Cu coordination effect. The degree of the chirality excess (DCE) value decreased with the increment of the concentration of Cu in the subphase. Furthermore, when the surface pressure increased, the DCE value of Cu-l/dGJ complexes increased gradually, which indicated that the Cu-l/dGJ complex aggregated into a chiral supramolecular structure through lateral molecular packing.
手性希夫碱与金属离子的协同作用为构建手性超分子自组装体提供了一种有效的策略。我们通过原位二次谐波线性二色性（SHG-LD）技术结合紫外可见光谱和原子力显微镜研究了两亲性希夫碱对映体 2-羟基-1-萘甲基氨基，' -双（十八烷基）-L / D-谷氨酸二酰胺（L / D-GJ）在空气/水界面上的超分子自组装。L-GJ 和 D-GJ 单层可以在不同的界面上形成彼此的镜像结构，这可以通过金属离子介导。当将 Mg 和 Zn 离子加入亚相中时，L / D-GJ 单层自组装成类似纳米纤维的结构，并表现出与纯水界面相似的显著手性。然而，当将 Cu 离子加入亚相中时，L / D-GJ 单层的手性被破坏，因为 Cu 具有配位作用。手性过量度（DCE）值随亚相中 Cu 浓度的增加而降低。此外，当表面压增加时，Cu-L / D-GJ 配合物的 DCE 值逐渐增加，这表明 Cu-L / D-GJ 配合物通过横向分子堆积聚集为手性超分子结构。
