Azulene-Based BN-Heteroaromatics

Azulene, a nonalternant bicyclic aromatic hydrocarbon, has unique chemical and physical properties and is considered to be a promising building block for constructing novel polycyclic aromatic hydrocarbons (PAHs) and heteroaromatics. We present here the first two azulene-based BN-heteroaromatics Az-BN-1 and Az-BN-2. The chemical structures and optical and electrochemical properties of both compounds have been investigated, as well as their sensing behavior in response to fluoride ion. Az-BN-1 and Az-BN-2 show different photophysical properties from other reported BN-embedded PAHs, such as lower band gaps and unusual fluorescence. In addition, Az-BN-1 and Az-BN-2 exhibit unexpected deboronization upon addition of trifluoroacetic acid, which distinguishes them from other reported BN-heteroaromatics and can be ascribed to the unique property of the azulene unit.