Lighting up azobenzene

An azobenzene derivative that fluoresces more intensely than any other azobenzene compound has been synthesized by chemists in Japan (Chem. Commun., DOI: 10.1039/b615966d). Azobenzene and its derivatives are widely used commercially as dyes, but they generally exhibit little or no fluorescence because they tend to isomerize when irradiated with light. The new derivative (shown) was prepared by Junro Yoshino, Naokazu Kano, and Takayuki Kawashima at the University of Tokyo. Its structure features a tight, intramolecular boron-nitrogen dative bond, which provides rigidity for the structure around the azo group, and two strongly electron-withdrawing pentafluorophenyl groups. Upon irradiation, the compound glows green with a light-emitting efficiency 30,000 times greater than that of unsubstituted azobenzene. The new compound will expand the possibilities of employing azobenzenes as fluorescent materials for chemical sensors, fluorescent probes, and other light-emitting devices, according to the authors. "The future challenge for this work will be tuning the emission wavelength and improving the fluorescence quantum yield by modifying the substituents," Kawashima says.