Bi Yuting, Wang Zhi, Liu Tong, Sun Di, Godbert Nicolas, Li Hongguang, Hao Jingcheng, Xin Xia
Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Ji'nan 250100, People's Republic of China.
MAT_INLAB (Laboratorio di Materiali Molecolari Inorganici), Centro di Eccelenza CEMIF.CAL, LASCAMM CR-INSTM della Calabria, Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, 87036, Arcavacata di Rende (CS), Italy.
ACS Nano. 2021 Oct 26;15(10):15910-15919. doi: 10.1021/acsnano.1c03824. Epub 2021 Sep 20.
Chiral assembly of metal nanoparticles (NPs) into complex superstructures has been widely studied, but their formation mechanisms still remain mysterious due to the lack of precise structural information from the metal-organic interface to metallic kernel. As "molecular models" of metal NPs, atomically precise metal nanoclusters (NCs) used in the assembly of a macroscale superstructure will provide details of microscopic structure for deep understanding of such highly sophisticated assemblies; however, chiral superstructures have not been realized starting from achiral metal NCs with atomic precision. Herein, we report the supramolecular assembly of a water-soluble silver NC ((NH)[Ag(mba)], Hmba = 2-mercaptobenzoic acid, abbreviated as Ag-NCs hereafter) into chiral hydrogels induced by the coordination of secondary metal ions. Single crystal X-ray diffraction reveals the triskelion-like structure of Ag-NCs with a pseudochiral conformation caused by special arrangement of the peripheral mba ligands. The enantioselective orientation of the peripheral carboxyl group facilitates the assembly of Ag-NCs into nanotubes with a chiral cubic (*) lattice when coordinating to Ba. The nanotubes can further intertwine into one-dimensional chiral nanobraids with a preferred left-handed arrangement. These multiple levels of chirality can be tuned by drying, during which the * phase is missing but the chiral entanglement of the nanotubes is enhanced. Through the gelation of atomically precise, achiral NCs coordination of secondary metal ions, chiral amplification of superstructures was realized. The origination of the chirality at different length scales was also discussed.
金属纳米颗粒（NPs）手性组装成复杂的超结构已得到广泛研究，但由于从金属-有机界面到金属核缺乏精确的结构信息，其形成机制仍然成谜。作为金属NPs的“分子模型”，用于组装宏观超结构的原子精确金属纳米团簇（NCs）将提供微观结构细节，以深入理解这种高度复杂的组装；然而，从具有原子精确性的非手性金属NCs出发尚未实现手性超结构。在此，我们报道了通过二级金属离子配位将水溶性银纳米团簇（(NH)[Ag(mba)]，Hmba = 2-巯基苯甲酸，以下简称为Ag-NCs）超分子组装成手性水凝胶。单晶X射线衍射揭示了Ag-NCs的三臂状结构，其具有由外围mba配体的特殊排列引起的假手性构象。外围羧基的对映选择性取向在与Ba配位时促进Ag-NCs组装成具有手性立方（）晶格的纳米管。纳米管可进一步缠绕成具有优选左手排列的一维手性纳米辫。这些多层次的手性可以通过干燥来调节，在此过程中相消失，但纳米管的手性缠结增强。通过原子精确的非手性NCs与二级金属离子的配位凝胶化，实现了超结构的手性放大。还讨论了不同长度尺度上手性的起源。
