Mechanistic aspects of diazaquinone chemiluminescence

Twelve cyclic hydrazides of aromatic and heterocyclic o-dicarboxylic acids were converted into diazaquinones by treatment with t-butyl hypochlorite. Chemiluminescence was produced from all diazaquinones on treatment with HO2- derived from hydrogen peroxide and potassium hydroxide. Diazaquinones derived from pyridine and pyrazine o-dicarboxylic acid hydrazides afforded chemiluminescence with hydrogen peroxide alone. Such nitrogen bases and N-oxides increase the nucleophilicity of hydrogen peroxide by complex formation and this effect was also exemplified by observation of chemiluminescence from phthalazine-1,4-diones, hydrogen peroxide and either pyridine or pyridine N-oxide. Highly reactive diazaquinones emit light with aqueous alkali and oxygen. No chemiluminescence was produced with organic bases and oxygen which suggests the involvement of a different mechanism compared with the hydroperoxide anion case.