CC BY-NC-ND 4.0 · Organic Materials 2021; 03(02): 119-127
DOI: 10.1055/s-0041-1726089
Focus Issue: Peter Bäuerle 65th Birthday
Original Article

Unusual Zig-Zag Effect in the Electrochemical Oxidation of Phenyl End-Capped α-Oligothiophenes

Kevin Bold
a  Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
,
Matthias Stolte
a  Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
b  Center for Nanosystems Chemistry, Universität Würzburg, Theodor-Boveri-Weg, 97074 Würzburg, Germany
,
a  Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
b  Center for Nanosystems Chemistry, Universität Würzburg, Theodor-Boveri-Weg, 97074 Würzburg, Germany
› Author Affiliations


Abstract

A series of phenyl end-capped α-oligothiophenes containing four to seven thiophene subunits (4T7T) was synthesized utilizing palladium-catalyzed cross-coupling reactions. UV/Vis spectroscopic analysis revealed one broad absorption band that shifts bathochromically with increasing number of thiophene units. Structured emission spectra are observed with Stokes shift ν~4000 cm−1 and quantum yields of up to 53%. End-capping of the oligothiophene molecules by phenyl units does not only extend the effective conjugation but also prevents from α–α-homocoupling upon electrochemical oxidation. Accordingly, reversible redox waves are observed in cyclic voltammetry with up to four reversible one-electron processes for the two longer congeners. Analyses of the first two oxidation processes in the framework of multiredox systems provide insight into the stabilization or destabilization of polaronic and bipolaronic states. An unusual zig-zag trend for the first (and to a lesser extend second) oxidation process could be explained by the sterical encumbrance of solubilizing hexyl chains in 5T and 7T molecules which counteract the formation of a fully planar quinoidal oligothiophene backbone.

Supporting Information

Supporting information for this article is available online at https://doi.org/10.1055/s-0041-1726089.


Dedicated to Professor Peter Bäuerle on the occasion of his 65th birthday.


Supporting Information



Publication History

Received: 16 January 2021

Accepted: 27 January 2021

Publication Date:
01 April 2021 (online)

© 2021. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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