Discovery of a novel family of polycyclic aromatic molecules with unique reactivity and members valuable for fluorescent sensing and medicinal chemistry

A novel polycyclic aromatic molecule, i.e. 1-oxo-1H-phenalene-2,3-dicarbonitrile (compound 1, initially misidentified as 8-oxo-8H-acenaphtho[1,2-b]pyrrolecarbonitrile) was discovered by our group in 2005. This parent compound is highlighted for its unique oxidative S_NAr^H (nucleophilic substitution of aromatic hydrogen) reactivity that provides easy approaches to diverse derivatives with different long-wavelength fluorescence and important biological activities. To date, a large number of derivatives have been synthesized and evaluated by several international research groups, indicating the formation of a new and valuable family of functional chemicals. Some members have been functionalized for molecular or nanoparticle-based probes applicable in chemical and environmental sensing, biomolecule imaging and tumor diagnosis. Others have qualified as high potency anticancer agents specifically targeting different functional proteins in tumor cells. With regard to the increasing attention paid to this new chemical family, it is a good time to review major achievements in order to promote further and deeper investigation.