Boron-containing π-conjugated molecules offer a substantial application potential in the field of organic electronics. During the last decade, aryl(hydro)boranes have established themselves as versatile novel building blocks for sophisticated boron-doped materials. This perspective article comprehensively discusses key structural motifs and reactivity patterns of recently developed aryl(hydro)boranes and shows how these have been used for the synthesis of macromolecular organoboranes through hydroboration polymerisation, ring-opening polymerisation and condensation polymerisation protocols.

9,10-Dihydro-9,10-diboraanthracene (DBA) provides a versatile scaffold for the development of boron-doped organic luminophores. Symmetrically C-halogenated DBAs are obtained through the condensation of 4-bromo-1,2-bis(trimethylsilyl)benzene or 4,5-dichloro-1,2-bis(trimethylsilyl)benzene with BBr₃ in hexane. Unsymmetrically C-halogenated DBAs are formed via an electrophilic solvent activation reaction if the synthesis is carried out in o-xylene. Mechanistic insight has been achieved by in situ NMR spectroscopy, which revealed C-halogenated 1,2-bis(dibromoboryl)benzenes to be the key intermediates. Treatment of the primary 9,10-dibromo-DBAs with MesMgBr yields air- and water-stable C-halogenated 9,10-dimesityl-DBAs (2-Br-6,7-Me₂-DBA(Mes)₂; 2,6-Br₂-DBA(Mes)₂; 2,3-Cl₂-6,7-Me₂-DBA(Mes)₂; 2,3,6,7-Cl₄-DBA(Mes)₂). Subsequent Stille-type C–C-coupling reactions give access to corresponding phenyl, 2-thienyl, and p-N,N-diphenylaminophenyl derivatives, which act as highly emissive donor–acceptor dyads or donor–acceptor–donor triads both in solution and in the solid state. 2-Thienyl was chosen as a model substituent to show that already a variation of the number and/or the positional distribution of the donor groups suffices to tune the emission wavelength of the resulting benchtop stable compounds from 469 nm (blue) to 540 nm (green). A further shift of the fluorescence maximum to 594 nm (red) can be achieved by switching from 2-thienyl to p-aminophenyl groups. A comparison of the optoelectronic properties of selected C-substituted DBA(Mes)₂ derivatives with those of the isostructural anthracene analogues unveiled the following: (i) The DBA core is a much better electron acceptor. (ii) The emission colors of DBAs fall in the visible range of the spectrum (blue to orange), while anthracenes emit exclusively in the near-ultraviolet to blue wavelength regime. (iii) DBAs show significantly higher solid-state quantum yields.

Intramolecular Yamamoto coupling on a tetrabrominated triarylborane furnishes a highly fluorescent, soluble, air- and water-stable boron-doped [4]helicene.