Baumert Marcel E, Le Victoria, Su Po-Hua, Akae Yosuke, Bresser Dominic, Théato Patrick, Hansmann Max M
Faculty of Chemistry and Chemical Biology (CCB), Technical University Dortmund, Otto-Hahn-Str. 6, D-44227 Dortmund, Germany.
Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology (KIT), Engesserstr. 18, D-76131 Karlsruhe, Germany.
J Am Chem Soc. 2023 Oct 25;145(42):23334-23345. doi: 10.1021/jacs.3c09153. Epub 2023 Oct 12.
The search for new redox-active organic materials (ROMs) is essential for the development of sustainable energy-storage solutions. In this study, we present a new class of cyclobuta[]quinoxaline-1,2-diones or squaric acid quinoxalines (SQXs) as highly promising candidates for ROMs featuring exceptional stability and high redox potentials. While simple 1,2- and 1,3-squaric acid amides (SQAs), initially reported by Hünig and coworkers decades ago, turned out to exhibit low stability in their radical cation oxidation states, we demonstrate that embedding the nitrogen atoms into a quinoxaline heterocycle leads to robust two-electron SQX redox systems. A series of SQX compounds, as well as their corresponding radical cations, were prepared and fully characterized, including EPR spectroscopy, UV-vis spectroscopy, and X-ray diffraction. Based on the promising electrochemical properties and high stability of the new ROM, we developed SQX-functionalized polymers and investigated their physical and electrochemical properties for energy-storage applications. These polymers showed remarkable thermal stability well above 200 °C with reversible redox properties and potentials of about 3.6 V vs Li/Li. By testing the galvanostatic cycling performance in half-cells with lithium-metal counter electrodes, a styrene-based polymer with SQX redox side groups showed stable cycling for single-electron oxidation for more than 100 cycles. These findings render this new class of redox-active polymers as highly promising materials for future energy-storage applications.
寻找新型氧化还原活性有机材料（ROMs）对于可持续储能解决方案的发展至关重要。在本研究中，我们提出了一类新型的环丁烷并[ ]喹喔啉-1,2-二酮或方酸喹喔啉（SQXs），作为具有卓越稳定性和高氧化还原电位的ROMs的极具潜力的候选材料。虽然几十年前Hünig及其同事最初报道的简单1,2-和1,3-方酸酰胺（SQAs）在其自由基阳离子氧化态下表现出低稳定性，但我们证明将氮原子嵌入喹喔啉杂环会产生稳健的双电子SQX氧化还原体系。制备并全面表征了一系列SQX化合物及其相应的自由基阳离子，包括电子顺磁共振光谱、紫外-可见光谱和X射线衍射。基于这种新型ROM有前景的电化学性质和高稳定性，我们开发了SQX功能化聚合物，并研究了它们在储能应用中的物理和电化学性质。这些聚合物在200℃以上表现出显著的热稳定性，具有可逆的氧化还原性质，相对于Li/Li的电位约为3.6V。通过在使用锂金属对电极的半电池中测试恒电流循环性能，一种带有SQX氧化还原侧基的苯乙烯基聚合物在单电子氧化过程中显示出超过100次循环的稳定循环。这些发现使这类新型氧化还原活性聚合物成为未来储能应用中极具前景的材料。
