Tipping the polaron–bipolaron balance: concentration and spin effects in doped oligo(aniline)s observed by UV-vis-NIR and TD-DFT†,Molecular Systems Design & Engineering

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Tipping the polaron–bipolaron balance: concentration and spin effects in doped oligo(aniline)s observed by UV-vis-NIR and TD-DFT†
Molecular Systems Design & Engineering ( IF 3.2 ) Pub Date : 2018-12-04 00:00:00 , DOI: 10.1039/c8me00082d
Benjamin M. Mills _{1,

2,

3,

4} , Zhecheng Shao _{1,

2,

3,

4} , Stephanie R. Flynn _{1,

2,

3,

4} , Patrice Rannou _{5,

6,

7,

8,

9} , David M. Lindsay _{4,

10,

11,

12,

13} , Natalie Fey _{1,

2,

3,

4} , Charl F. J. Faul _{1,

2,

3,

4}

Affiliation

The oxidation states and doped forms of oligo(aniline)s are readily interconverted, and each state has characteristic UV-vis-NIR absorptions, making this spectroscopic technique ideal for in situ analysis of oligo(aniline) behaviour. However, experimental isolation of some of these states can be challenging and quantitative agreement between experimental and calculated spectra has been poor, making it difficult to identify the exact structure(s) and properties of each state. Here we report a comprehensive study of the UV-vis-NIR spectra of all oxidation states and doped forms of a series of oligo(aniline)s of varying lengths (dimer, tetramer and octamer), using a computationally inexpensive DFT method that is particularly suited to molecules with charge-transfer character. The computational study suggests that doped oligo(aniline)s form mixtures of spin isomers (polaronic and bipolaronic forms) in solution, and we have been able to evaluate and compare the most likely electronic configurations, as well as supporting our insights experimentally, by ESR spectroscopy. This doping approach enables tuning of the spin isomer equilibrium position by varying the concentration of protonic dopant, offering a new pathway to explore the electronic structure of π-conjugated molecules more generally, and opening up new approaches to the design of spintronic materials.

中文翻译：

改善极化子-双极化子的平衡：通过UV-vis-NIR和TD-DFT观察到的掺杂低聚（苯胺）中的浓度和自旋效应†

低聚（苯胺）的氧化态和掺杂形式易于相互转换，并且每个态都具有特征性的UV-vis-NIR吸收，这使这种光谱技术非常适合于原位分析低聚（苯胺）行为。但是，对其中某些状态的实验隔离可能具有挑战性，并且实验光谱与计算光谱之间的定量一致性很差，因此很难确定每种状态的确切结构和性质。在这里，我们使用计算上便宜的DFT方法，特别是一系列长度不等的寡聚（苯胺）（二聚体，四聚体和八聚体）的所有氧化态和掺杂形式的UV-vis-NIR光谱进行了全面的研究。适用于具有电荷转移特性的分子。计算研究表明，掺杂的低聚（苯胺）在溶液中形成自旋异构体（极化和双极化形式）的混合物，我们已经能够评估和比较最可能的电子构型，以及通过ESR光谱在实验上支持我们的见解。这种掺杂方法能够通过改变质子掺杂剂的浓度来调节自旋异构体的平衡位置，从而提供了一条更广泛地探索π共轭分子电子结构的新途径，并为自旋电子材料的设计开辟了新途径。

更新日期：2018-12-04

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