Synthesis and characterization of S,N-heterotetracenes

• Main Authors: Astrid Vogt, Florian Henne, Christoph Wetzel, Elena Mena-Osteritz, Peter Bäuerle
• Format: Article
• Language: English
• Published: Beilstein-Institut 2020-10-01
• Series: Beilstein Journal of Organic Chemistry
• Subjects: buchwald–hartwig amination; cadogan reaction; optoelectronic properties; s,n-heteroacene; structure–property relationship
• Online Access: https://doi.org/10.3762/bjoc.16.214

The synthesis and optoelectronic properties of novel S,N-heterotetracenes consisting of fused heterocyclic thiophene and pyrrole rings are presented. Tetracyclic and benzannulated derivatives with a varying number and sequence of sulfur and nitrogen heteroatoms were synthesized in multistep synthetic routes. A Buchwald–Hartwig amination of brominated precursors, thermolysis of azide precursors, and a Cadogan reaction of nitro-substituted precursors were successfully applied to eventually build-up pyrrole rings to stable and soluble fused systems. The various obtained heteroatom sequences ‘SSNS’ (SN4), ‘SNNS’ (SN4’’), and ‘NSSN’ (SN4’) allowed for evaluation of structure–property relationships relative to the sulfur analogue tetrathienoacene (‘SSSS’). In line with the results for the whole series of S,N-heteroacenes, we find that replacement of sulfur by nitrogen atoms in the tetra- and hexacyclic systems leads to a red-shift in absorption, a decrease in oxidation potential and energy gap. On the other hand, the replacement of a thiophene ring by benzene leads to the opposite effects.