Cu^II-Mediated Synthesis of a New Fluorescent Pyrido[1,2-<i>a</i>]quinoxalin-11-ium Derivative

Quinoxalines are heterocyclic compounds with potential application as drugs or fluorophores. However, few quinoxalinylium salts have been reported in the literature. This manuscript describes the synthesis and structural characterization of a previously unknown quinoxalinylium derivative, 2-aminopyrido[1,2-a]quinoxalin-11-ylium ([1]+), as perchlorate and thiocyanate salts from the CuII-mediated reaction of a Schiff base. The reaction is most efficient with CuII. The formation of a small quantity was observed spectroscopically in the presence of either a strong oxidizer or MnII. No product formation was observed with ZnII, CdII, FeII, or NiII. [1]+ emits at 580 nm, with a quantum yield estimated as 0.23, upon excitation at 470 nm.