Tetrazo[1,2-b]indazoles: Straightforward Access to Nitrogen-Rich Polyaromatics from s-Tetrazines

The straightforward access to a new class of aza-polyaromatics is reported. Starting from readily available fluorinated s-tetrazine, a cyclization process with azide leads to the formation of an unprecedented tetrazo[1,2-b]indazole or a bis-tetrazo[1,2-b]indazole (cis and trans conformers). Based on the new nitrogen core, further N-directed palladium-catalyzed ortho-C-H bond functionalization allows the introduction of halides or acetates. The physicochemical properties of these compounds were studied by a joint experimental/theoretical approach. The tetrazo[1,2-b]indazoles display solid-state π-stacking, low reduction potential, absorption in the visible range up to the near-infrared, and intense fluorescence, depending on the molecular structure.

Synthesis and properties of a novel decacyclic S,N-heteroacene

S,N-Heteroacene materials with fused multicyclic heteroaromatics have become increasingly attractive for organic optoelectronic device applications. In this work, the Cadogan ring-closure reaction between the benzene moiety of thieno[3,2-b]indole and 5,6-dinitrobenzo[c][1,2,5]thiadiazole was employed to prepare the novel decacyclic S,N-heteroacene 15,16-dibutyl-14,17-didodecyldithieno[2′′,3′′:2′,3′]indolo[6′,7′:4,5]pyrrolo[3,2-e:2′,3′-g][2,1,3]benzothiadiazole (TIP), C58H76N6S3. The conjugated backbone of TIP is extended in comparison with its octacyclic analogue as the central unit within Y6-type molecular acceptors, a family of overwhelming electron acceptors in polymer solar-cell research. The single-crystal X-ray diffraction (SC-XRD) characterization indicated the existence of π–π and C(sp 2)—H...π interactions among TIP molecules. The electrochemical and optical properties of TIP were also characterized. As a novel S,N-heteroacene building block, TIP is anticipated to be of potential use in the construction of promising electronic materials.