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Updated: Oct 1, 2025
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)
Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Impact of Heterocycle Annulation on NIR Absorbance in Quinoid Thioacene Derivatives
Peng Hou1, Sebastian Peschtrich1, Nils Huber2
1Chemistry Department, Paderborn University, Warburger Straße 100, 33098, Paderborn, 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 .
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