Not a natty BOH: Borepin‐based extended π‐electron molecules contain bulky substituents that shield the vacant boron p orbitals and allow synthetic manipulation and purification under ambient conditions. These borepin‐containing compounds (see picture; Mes*=1,3,5‐tris(tert‐butyl)phenyl; B orange, C gray) display reversible cathodic electrochemistry and can be viewed as n‐type analogues to bent acene hydrocarbons.

We present the synthesis and characterization of dibenzo[b,f]borepins (DBBs) functionalized at the para and meta position with respect to the boron center in order to understand how regiochemical issues influence photophysical and electrochemical properties. An expanded synthetic repertoire is presented, using palladium catalysis (to perform Stille, Suzuki, Buchwald-Hartwig, and Sonogashira cross-coupling reactions) and lithium-halogen exchange to synthesize a series of extended π-conjugated DBBs. These chemistries are enabled by the use of a sterically bulky Mes* (2,4,6-tri-tert-butylphenyl) group on boron and the inclusion of reactive bromide handles on the DBB core. Photophysical, electrochemical, and computational analyses of these compounds indicate that relative to the protio-DBB the installation of groups at the meta positions decreases the optical band gap while para substitution raises the electron affinity of the system. Thus, both the HOMO-LUMO gap and specific frontier molecular orbital levels can be tuned by the installation of different conjugated substituents.

The synthesis of new boron-containing acenes (meta-B-entacenes) is reported. These compounds exhibit slightly non-planar core geometries with blue-shifted spectral properties and more negative electrochemical reduction potentials relative to known para isomers. Polarizable π-extended architectures were realized via cross-coupling procedures with chloro-functionalized precursors.

The synthesis and characterization of functionalized bora-acenes (B-entacenes) where Stille and Sonogashira cross-couplings were used to attach a series of electron-donating and -withdrawing substituents is reported. Photophysical, electrochemical, and computational analyses revealed that the LUMO level can be tuned by changing the para-conjugated substituent. Furthermore, the dimethylamino-functionalized molecule exhibited intense solvatochromism due to the intramolecular charge-transfer interaction.

Heteroaromatisches Bor: Sperrige Substituenten in Borepin‐Derivaten mit erweitertem π‐Elektronensystem schirmen die unbesetzten p‐Orbitale des Bors ab (siehe Bild; Mes*=1,3,5,‐Tris(tert‐butyl)phenyl, B orange, C grau), was die Handhabung und Reinigung dieser Verbindungen unter Umgebungsbedingungen möglich macht. Die Verbindungen zeigen reversibles elektrochemisches Verhalten und können als n‐leitende Analoga gekrümmter Acene betrachtet werden.