Simple Air‐Stable [3]Radialene Anion Radicals as Environmentally Switchable Catholytes in Water
Simple Air‐Stable [3]Radialene Anion Radicals as Environmentally Switchable Catholytes in Water
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简单空气 - 稳定 [3]Radialene 阴离子自由基作为水中环境可切换的阴极电解液
DOI：
10.1002/chem.202302829
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Bejger, Christopher M.
中科院分区：
文献类型：
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作者：
Hasan, Fuead;Gillen, Jonathan H.;Jayaweera, Amaya T.;McDearmon, Jr., William D.;Winter, Arthur H.;Bejger, Christopher M.
六氰基[3]放射性烯自由基阴离子（1）是用于氧化还原液流电池（RFB）应用的有吸引力的阴极电解质材料。用酯部分取代氰基增强溶解度，同时保持氧化还原可逆性和有利的氧化还原电位。在这里，我们表明，这些酯官能化的，六取代的[3]radialene自由基阴离子在水中可逆地二聚。二聚化模式取决于取代模式，并且可以在溶液中切换。刺激响应行为是通过利用前所未有的三态转换机制来实现的，其中自由基可以在自由基，π-二聚体和σ-二聚体之间切换-每个都具有显着不同的光学，磁性和氧化还原特性-通过改变溶剂环境，温度或盐度。对称的三酯-三氰基[3]径向烯（3）在水中形成溶剂响应性的σ-二聚体，其在添加有机溶剂时转化为自由基阴离子或在盐水溶液中转化为π-二聚体。二酯-四氰基[3]放射烯（2）在水溶液中主要以π-二聚体形式存在，在有机溶剂中主要以自由基阴离子形式存在。在甲醇溶液中，2和3的二聚行为都与温度有关。在静态H电池中恒电流充放电循环期间，二聚化平衡对阴极电解液稳定性具有直接影响。具体而言，有利于自由基阴离子或π-二聚体的条件表现出显著增强的循环特征。
The hexacyano[3]radialene radical anion (1) is an attractive catholyte material for use in redox flow battery (RFB) applications. The substitution of cyano groups with ester moieties enhances solubility while maintaining redox reversibility and favorable redox potentials. Here we show that these ester‐functionalized, hexasubstituted [3]radialene radical anions dimerize reversibly in water. The dimerization mode is dependent on the substitution pattern and can be switched in solution. Stimuli‐responsive behavior is achieved by exploiting an unprecedented tristate switching mechanism, wherein the radical can be toggled between the free radical, a π‐dimer, and a σ‐dimer‐each with dramatically different optical, magnetic, and redox properties‐by changing the solvent environment, temperature, or salinity. The symmetric, triester‐tricyano[3]radialene (3) forms a solvent‐responsive, σ‐dimer in water that converts to the radical anion with the addition of organic solvents or to a π‐dimer in brine solutions. Diester‐tetracyano[3]radialene (2) exists primarily as a π‐dimer in aqueous solutions and a radical anion in organic solvents. The dimerization behavior of both2and3is temperature dependent in methanol solutions. Dimerization equilibrium has a direct impact on catholyte stability during galvanostatic charge–discharge cycling in static H‐cells. Specifically, conditions that favor the free radical anion or π‐dimer exhibit significantly enhanced cycling profiles.