Diborepins: New Classes of Heteroaromatic Building Blocks for Extended Conjugated Materials

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1,2,7-Azadiborepins constitute a new class of heteroaromatic compounds with six pi electrons. Dithieno-fused 1,2,7-azadiborepins are structurally and electronically related to bithiophene imide (BTI), a well-established electron-deficient organic building block for n-type semiconducting materials. From the latter, the newly devised tricyclic organoboron compounds are formally derived by the substitution of a strongly electron-withdrawing BAr-NR-BAr moiety for the dicarboximide group. This offers the additional opportunity of fine-tuning their properties through the variable substituents (Ar) on boron. The aim of this project is to develop 1,2,7-azadiborepins and further classes of novel diborepins with different heteroatoms (E = O, P, S) in their B-E-B unit and with or without further aromatic rings fused. Detailed experimental and theoretical studies will provide fundamental insight into the aromatic character of their constituent rings. The anticipated weak aromaticity of the diboron heterocycles should confer sufficient stability while ensuring effective conjugation with the adjacent pi systems. A variety of diborepin-based materials with specifically tailored properties and functions will be targeted by incorporating the novel heterocyclic building blocks into extended frameworks including conjugated polymers, oligomers, and macrocylces. Incorporation into ladder oligomers and semiladder polymers is expected to impart substantial additional stability and lead to modified solid-state packing motifs. The optoelectronic properties of the new materials as well as sensory capabilities and possible host-guest interactions will be explored.