Tipping the polaron–bipolaron balance: concentration and spin effects in doped oligo(aniline)s observed by UV-vis-NIR and TD-DFT

Benjamin M. Mills, Zhecheng Shao, Stephanie R. Flynn, Patrice Rannou, David M. Lindsay, Natalie Fey, Charl F. J. Faul

Research output: Contribution to journalArticle

Abstract

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.
LanguageEnglish
Pages103-109
Number of pages7
JournalMolecular Systems Design & Engineering
Volume4
Issue number1
Early online date4 Dec 2018
DOIs
Publication statusPublished - 1 Feb 2019

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Gene Conversion
Aniline
Discrete Fourier transforms
Isomers
Doping (additives)
Oxidation
Magnetoelectronics
Molecules
Dimers
Electronic structure
Paramagnetic resonance
Charge transfer
Tuning
Spectroscopy
aniline

Keywords

  • DFT calculations
  • redox-active materials
  • oligo(aniline)s

Cite this

Mills, Benjamin M. ; Shao, Zhecheng ; Flynn, Stephanie R. ; Rannou, Patrice ; Lindsay, David M. ; Fey, Natalie ; Faul, Charl F. J. / Tipping the polaron–bipolaron balance : concentration and spin effects in doped oligo(aniline)s observed by UV-vis-NIR and TD-DFT. In: Molecular Systems Design & Engineering. 2019 ; Vol. 4, No. 1. pp. 103-109.
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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. / Mills, Benjamin M.; Shao, Zhecheng; Flynn, Stephanie R.; Rannou, Patrice; Lindsay, David M.; Fey, Natalie; Faul, Charl F. J.

In: Molecular Systems Design & Engineering, Vol. 4, No. 1, 01.02.2019, p. 103-109.

Research output: Contribution to journalArticle

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AU - Mills, Benjamin M.

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AU - Fey, Natalie

AU - Faul, Charl F. J.

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