Impact of Heterocycle Annulation on NIR Absorbance in Quinoid Thioacene Derivatives

Peng Hou; Sebastian Peschtrich; Nils Huber; Wolfram Feuerstein; Angela Bihlmeier; Ivo Krummenacher; Roland Schoch; Wim Klopper; Frank Breher; Jan Paradies

doi:10.1002/chem.202200478

Impact of Heterocycle Annulation on NIR Absorbance in Quinoid Thioacene Derivatives

Chemistry. 2022 Apr 22;28(23):e202200478. doi: 10.1002/chem.202200478. Epub 2022 Mar 29.

Authors

Affiliations

¹ Chemistry Department, Paderborn University, Warburger Straße 100, 33098, Paderborn, Germany.
² Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), Kaiserstraße 12, 76131, Karlsruhe, Germany.
³ Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstraße 15, 76131, Karlsruhe, Germany.
⁴ Institute of Inorganic Chemistry, University of Würzburg, Am Hubland, 97074, Würzburg, Germany.

Abstract

The synthesis and characterisation of a homologous series of quinoid sulfur-containing imidazolyl-substituted heteroacenes is described. The optoelectronic and magnetic properties were investigated by UV/vis, fluorescence and EPR spectroscopy as well as quantum-chemical calculations, and were compared to those of the corresponding benzo congener. The room-temperature and atmospherically stable quinoids display strong absorption in the NIR region between 678 and 819 nm. The dithieno[3,2-b:2',3'-d]thiophene and the thieno[2',3':4,5]thieno[3,2-b]thieno[2,3-d]thiophene derivatives were EPR active at room temperature. For the latter, variable-temperature EPR spectroscopy revealed the presence of a thermally accessible triplet state, with a singlet-triplet separation of 14.1 kJ mol^-1 .

Keywords: EPR spectroscopy; UV spectroscopy; density functional theory; heteroacenes; radicals.

Grants and funding

PA1562/14-1/Deutsche Forschungsgemeinschaft