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 borane moieties that show effective internal ?-conjugation involving the respective boron centers and adjacent hetaryl groups. Conjugation between both units, however, is disrupted by aliphatic linker. Cyclic voltammetry revealed minimal electronic communication centers, as evidenced closely spaced reduction processes. UV-vis spectra showed bathochromic shifted absorption bands compared to related monoboranes, which attributed methylene bridge. further red-shift results upon introduction methyl or SiMe3 groups at terminal thiophene rings.