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

Abstract

The synthesis of four N-functionalized bis[1]benzothieno[3,2-b:2′,3′-d]pyrroles (BBTPs) is reported in order to provide a more detailed characterization of these fused-ring units, as well as increase the scope of known BBTP units available for application to conjugated materials. The optical, electronic, and structural properties of the resulting BBTP units have been compared to the parent N-alkyl- and N-aryl-dithieno[3,2-b:2′,3′-d]pyrroles (DTPs), as well as their corresponding 2,6-diphenyl derivatives, in order to fully quantify the relative electronic effects resulting from benzannulation of the parent DTP building block. Such comparative analysis reveals that benzannulation results in a red-shifted absorbance, but to a lesser extent than simple phenyl-capping of the DTP. More surprising is that benzannulation results in stabilization of the BBTP HOMO, compared to the destabilization normally observed with extending the conjugation length of the backbone.

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

“…However, in comparison to the respective dithieno[2,3‐ b :3′,2′‐ e ][1,4]thiazines the first oxidation potentials are shifted anodically. These findings are in agreement with the potential differences between dithieno[3,2‐ b :2′,3′‐ d ]pyrroles and bis[1]benzothieno[3,2‐ b :2′,3′‐ d ]pyrroles . In the series of the three regioisomers, anti ‐ anti BBTTs are easiest to oxidize (for HOMO energy levels see the Supporting Information).…”

“…[6a] However,i nc omparison to the respective dithieno[2,3-b:3',2'-e] [1,4]thiazines the first oxidation potentials are shifted anodically.T hese findings are in agreement with the potential differences between dithieno [3,2-b:2',3'-d]pyrroles andb is [1]benzothieno [3,2-b:2',3'd]pyrroles. [22] In the series of the three regioisomers, anti-anti BBTTsa re easiest to oxidize( for HOMO energy levels see the Supporting Information). Interestingly,t he gap of the first potential is largest between the syn-syn and the syn-anti BBTT, also as ac onsequence of the most pronounced structurald ifferences between theset wo regioisomers.…”

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

“…Starting from the phenothiazine novel anellated 1,4-thiazines, such as 4 H -dithieno­[2,3- b :3′,2′- e ]­[1,4]­thiazine, were created, aiming for an elevation of the HOMO energy level . In this context, the ring-closing Buchwald–Hartwig coupling is an excellent tool, furnishing N -heterocycles …”