The most intensely fluorescent azobenzene molecule to date has been discovered by Japanese scientists. It is substituted with a boron group and shows 30 000 fold light emitting efficiency compared to the unsubstituted azobenzene. 

Azo dyes, derivatives of azobenzene, are very frequently used as dyes. They are photoresponsive molecules, and act as chromophores. However the azobenzene itself does not emit light. Takayuki Kawashima and coworkers from the University of Tokyo, were studying the effects of adding main group substituents to the nitrogen in the 2-position of the azobenzene. They found that the interaction between boron and this nitrogen makes the molecule intensely fluorescent. 

The group expect that this will create more options for making fluorescent probes, chemical sensors and other light emitting devices. According to Kawashima, the future challenge for this work will be tuning the emission wavelength and improving the fluorescence quantum yield by modifying the substituents. 

Katherine Vickers