Turning on Fluorescent Emission from C-Alkylation on Quinoxaline Derivatives

Reduction on imine moiety (CN) of quinoxalines by alkyl-/aryllithiums led to a geometrical change on the quinoxaline ring, thereby perturbing the electronic structure to turn on fluorescence emission. Such a structural change resulted in interrupted cyclic-ring systems with electron-donating amine (sp3-type) and electron-accepting imine (sp2-type) units bridged by a phenylene unit. Through either alkylation or arylation, a highly polarized electron donor−electron acceptor bipolar system was established in a single molecule with dramatically enhanced PL efficiency (up to 60%).