Conjugated Bis(triarylboranes) with Disconnected Conjugation

A series of methylene-bridged bis(triarylboranes) has been synthesized via two complementary routes using metal-free catalytic Si/B exchange condensation under mild conditions. The title compounds comprise two borane moieties that show effective internal pi-conjugation involving the respective boron centers and the adjacent hetaryl groups. Conjugation between both borane units, however, is disrupted by the aliphatic linker. Cyclic voltammetry revealed minimal electronic communication between the boron centers, as evidenced by two closely spaced reduction processes. The UV-vis spectra showed bathochromic shifted absorption bands compared to related monoboranes, which is attributed to the methylene bridge. A further red-shift results upon introduction of methyl or SiMe3 groups at the terminal thiophene rings.

Automated summary

A series of methylene-bridged bis(triarylboranes) were successfully synthesized using metal-free catalytic Si/B exchange condensation under mild conditions. These compounds exhibit effective internal pi-conjugation, but the conjugation between the two borane units is disrupted by the aliphatic linker. Cyclic voltammetry and UV-vis spectra further revealed the electronic structure properties of the compounds.