Chiral Redox-Active Isosceles Triangles

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• 作者：Siva Krishna Mohan Nalluri ; Zhichang Liu ; Yilei Wu ; Keith R. Hermann ; Avik Samanta ; Dong Jun Kim ; Matthew D. Krzyaniak ; Michael R. Wasielewski ; J. Fraser Stoddart
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：May 11, 2016
• 年：2016
• 卷：138
• 期：18
• 页码：5968-5977
• 全文大小：724K
• 年卷期：0
• ISSN：1520-5126

文摘

Designing small-molecule organic redox-active materials, with potential applications in energy storage, has received considerable interest of late. Herein, we report on the synthesis, characterization, and application of two rigid chiral triangles, each of which consist of non-identical pyromellitic diimide (PMDI) and naphthalene diimide (NDI)-based redox-active units. ¹H and ¹³C NMR spectroscopic investigations in solution confirm the lower symmetry (C₂ point group) associated with these two isosceles triangles. Single-crystal X-ray diffraction analyses reveal their rigid triangular prism-like geometries. Unlike previously investigated equilateral triangle containing three identical NDI subunits, both isosceles triangles do not choose to form one-dimensional supramolecular nanotubes by dint of [C–H···O] interaction-driven columnar stacking. The rigid isosceles triangle, composed of one NDI and two PMDI subunits, forms—in the presence of N,N-dimethylformamide—two different types of intermolecular NDI–NDI and NDI–PMDI π–π stacked dimers with opposite helicities in the solid state. Cyclic voltammetry reveals that both isosceles triangles can accept reversibly up to six electrons. Continuous-wave electron paramagnetic resonance and electron–nuclear double-resonance spectroscopic investigations, supported by density functional theory calculations, on the single-electron reduced radical anions of the isosceles triangles confirm the selective sharing of unpaired electrons among adjacent redox-active NDI subunit(s) within both molecules. The isosceles triangles have been employed as electrode-active materials in organic rechargeable lithium-ion batteries. The evaluation of the structure–performance relationships of this series of diimide-based triangles reveals that the increase in the number of NDI subunits, replacing PMDI ones, within the molecules improves the electrochemical cell performance of the batteries.