Chung H T Katie, Schramm Tim K, Head-Gordon Martin, Shee James, Toste F Dean
Department of Chemistry, University of California, Berkeley, California 94720, United States.
Chemical Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States.
J Am Chem Soc. 2025 Jan 15;147(2):2115-2128. doi: 10.1021/jacs.4c16027. Epub 2025 Jan 2.
Developing multicharge and spin stabilization strategies is fundamental to enhancing the lifetime of functional organic materials, particularly for long-term energy storage in multiredox organic redox flow batteries. Current approaches are limited to the incorporation of electronic substituents to increase or decrease the overall electron density or bulky substituents to sterically shield reactive sites. With the aim to further expand the molecular toolbox for charge and spin stabilization, we introduce regioisomerism as a scaffold-diversifying design element that considers the collective and cumulative electronic and steric contributions from all of the substituents based on their relative regioisomeric arrangements. Through a systematic study of regioisomers of near-planar aromatic cyclic triindoles and nonplanar nonaromatic cyclic tetraindoles, we demonstrate that this regioisomeric engineering strategy significantly enhances the H-cell cycling stability in the above two new classes of 2e catholytes, even when current strategies failed to stabilize the multicharged species. Density functional theory calculations reveal that the strategy operates by redistributing the charge and spin densities while highlighting the role of aromaticity in charge stabilization. The most stable 2e catholyte candidate was paired with a viologen derivative anolyte to achieve a proof-of-concept all-organic flow battery with 1.26-1.49 V, 98% capacity retention, and only 0.0117% fade/h and 0.00563% fade/cycle over 400 cycles (192 h), which is the highest capacity retention ever reported over 400 cycles in a multielectron all-organic flow battery setup. We anticipate regioisomeric engineering to be a promising strategy complementary to conventional electronic and steric approaches for multicharge and spin stabilization in other functional organic materials.
开发多电荷和自旋稳定策略是延长功能性有机材料寿命的基础，特别是对于多氧化还原有机液流电池中的长期能量存储。目前的方法仅限于引入电子取代基以增加或降低整体电子密度，或引入体积较大的取代基以空间屏蔽反应位点。为了进一步扩展用于电荷和自旋稳定的分子工具箱，我们引入区域异构作为一种支架多样化设计元素，该元素基于取代基的相对区域异构排列考虑所有取代基的集体和累积电子及空间贡献。通过对近平面芳香族环状三吲哚和非平面非芳香族环状四吲哚的区域异构体进行系统研究，我们证明了这种区域异构工程策略显著提高了上述两类新型双电子阴极电解液中的H电池循环稳定性，即使当前策略无法稳定多电荷物种。密度泛函理论计算表明，该策略通过重新分布电荷和自旋密度来发挥作用，同时突出了芳香性在电荷稳定中的作用。最稳定的双电子阴极电解液候选物与紫精衍生物阳极电解液配对，实现了概念验证的全有机液流电池，其电压为1.26 - 1.49 V，容量保持率为98%，在400次循环（192小时）中仅以0.0117%/小时和0.00563%/循环的速率衰减，这是多电子全有机液流电池装置中400次循环以来报道的最高容量保持率。我们预计区域异构工程将成为一种有前景的策略，可补充传统的电子和空间方法，用于其他功能性有机材料中的多电荷和自旋稳定。
