Conjugated Diphenylaniline-Azulene Co-Oligomers with Intense Absorption and Emission in the Visible Region

New conjugated 2,6-diphenylaniline-azulene co-oligomers of linear and branched structure were synthesized by the interaction of borylazulenes with diphenylaniline bromides under Suzuki-Miyaura cross-coupling conditions. The obtained diphenylaniline-azulene co-oligomers intensively absorb and emit visible light (410-700 nm region); in particular, they exhibit strong emissions in the green, as well as orange, range, with maxima of 510/590 nm. It is shown that such properties appear as a result of the positive resonance exposure to aniline fragments significantly rearranging the electronic structure of azulene, in particular, the levels and energy gaps of frontal HOMO-LUMO orbitals.