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Addressing the Elusive Polaronic Nature of Multiple Redox States in a π‐Conjugated Ladder‐Type Polymer
Advanced Electronic Materials ( IF 5.3 ) Pub Date : 2020-12-04 , DOI: 10.1002/aelm.202000786
Daniele Fazzi 1 , Fabrizia Negri 2
Affiliation  

Poly(benzimidazole–benzophenanthroline) (BBL) is a ladder‐type conjugated polymer showing remarkable charge transport properties. Upon doping it displays various conductive regimes, leading to two insulator‐to‐conductor transitions. Such transitions are never fully characterized, limiting understanding of its charged states. Open issues are: i) the electron/hole polaron relaxations, ii) the structure–function relationships of multiple redox states and their connection with the conductive regimes, and iii) the role of protonation. Such knowledge‐gaps are tackled via a comprehensive computational investigation of multiple redox species. Polarons show polyradicaloid character, as revealed by combining broken‐symmetry density functional theory, fragment orbital density, and multireference analysis. Electron/hole polaron relaxations occur on the polymer chain, the former localizing on the benzophenanthroline moieties, the latter on the benzimidazole units. Modeling of multiple charged species, up to one electron per repeat unit (1 eru), reveals a complex scenario of quasidegenerate states each featuring different spin multiplicity. Four redox states are responsible for the BBL insulator‐to‐conductor transitions. The two high conductive states refer to the electron polaron (0.25 eru) and the redox species with 0.75 eru. The insulating regimes refer to the bipolaron (0.50 eru) and the redox state with 1 eru. Protonation is modeled, revealing polaron‐like features in the spectroscopic properties.

中文翻译:

解决π共轭梯形聚合物中多个氧化还原态的难以捉摸的极化性质

聚苯并咪唑-苯并菲咯啉(BBL)是一种梯型共轭聚合物,具有出色的电荷传输性能。掺杂后,它会显示各种导电状态,从而导致两个绝缘体到导体的过渡。这种转变从未得到充分表征,从而限制了对其充电状态的理解。未解决的问题是:i)电子/空穴极化子弛豫; ii)多个氧化还原态的结构-功能关系及其与导电体系的联系;以及iii)质子化的作用。通过对多种氧化还原物质进行全面的计算研究,可以解决此类知识缺口。极化子显示出多自由基特征,这是通过结合破对称密度泛函理论,碎片轨道密度和多参考分析揭示出来的。电子/空穴极化子弛豫发生在聚合物链上,前者位于苯并菲咯啉部分,后者位于苯并咪唑单元上。多个带电物质的模型,每个重复单元最多1个电子(1 eru),揭示了复杂的准生成态的情况,每个生成态具有不同的自旋多重性。四个氧化还原状态负责BBL绝缘体到导体的过渡。两种高导电态是指电子极化子(0.25 eru)和0.75 eru的氧化还原物质。绝缘状态是指双极子(0.50 eru)和具有1 eru的氧化还原状态。对质子化进行了建模,揭示了光谱性质中类似于极化子的特征。每个重复单元最多1个电子(1 eru),揭示了一个复杂的准生成态态,每个态具有不同的自旋多重性。四个氧化还原状态负责BBL绝缘体到导体的过渡。两种高导电态是指电子极化子(0.25 eru)和0.75 eru的氧化还原物质。绝缘状态是指双极子(0.50 eru)和具有1 eru的氧化还原状态。对质子化进行了建模,揭示了光谱性质中类似于极化子的特征。每个重复单元最多1个电子(1 eru),揭示了一个复杂的准生成态态,每个态具有不同的自旋多重性。四个氧化还原状态负责BBL绝缘体到导体的过渡。两种高导电态是指电子极化子(0.25 eru)和0.75 eru的氧化还原物质。绝缘状态是指双极子(0.50 eru)和具有1 eru的氧化还原状态。对质子化进行了建模,揭示了光谱性质中类似于极化子的特征。绝缘状态是指双极子(0.50 eru)和具有1 eru的氧化还原状态。对质子化进行了建模,揭示了光谱性质中的类似于极化子的特征。绝缘状态是指双极子(0.50 eru)和具有1 eru的氧化还原状态。对质子化进行了建模,揭示了光谱性质中类似于极化子的特征。
更新日期:2021-01-14
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