Synthesis and Characterization of Bis[1]benzothieno[3,2-b:2',3'-d]pyrroles: Quantitative Effects of Benzannulation on Dithieno[3,2-b:2',3'-d]pyrroles

Game of Isomers: Bifurcation in the Catalytic Formation of Bis[1]benzothieno[1,4]thiazines with Conformation-Dependent Electronic Properties

Two regioisomers of bis[1]benzothieno[1,4]thiazine are unexpectedly obtained by tuning the catalytic conditions of the intermolecular-intramolecular Buchwald-Hartwig amination. Mechanistic insights and evidence of intermediates support a conclusive mechanistic rationale. Furthermore, a computationally based study on the influence of conformational aspects on the HOMO energy level of anellated 1,4-thiazine paves the way to enhance the electronic properties, thus successfully achieving higher luminescent and easier oxidizable syn- syn bis[1]benzothieno[1,4]thiazines.

Bis[1]benzothieno[1,4]thiazines: Planarity, Enhanced Redox Activity and Luminescence by Thieno-Expansion of Phenothiazine

Twofold Buchwald-Hartwig aminations selectively furnish three regioisomers of bis[1]benzothieno[1,4]thiazines; X-ray structure analyses and DFT calculations were corroborated for correlation of their electronic properties. All regioisomers outscore the parent compound phenothiazine with respect to a low-lying oxidation potential and reversible redox activity. The anti-anti bis[1]benzothieno[3,2-b:2',3'-e][1,4]thiazines possess the lowest oxidation potentials in this series and displayed pronounced green luminescence in solution (Φ_F ≈20 %) and in the solid state. Syn-anti regioisomers were only weakly luminescent in solution, but showed aggregation-induced emission enhancement and solid-state luminescence. Most interestingly, X-ray structure analyses revealed that anti-anti derivatives have an amazingly coplanar structure of the pentacyclic anellated 1,4-thiazine system, emphasizing a structural similarity to heteroacenes. The calculated theoretical nucleus-independent chemical shifts additionally suggested that these 8π-electron core systems can be considered as the first electronically unbiased anellated 1,4-thiazines with antiaromatic character.