Study of the characteristics of three high-energy intermediates generated in peroxyoxalate chemiluminescence (PO-CL) reactions

摘要

Perylene emission intensity generated from peroxyoxalate chemiluminescence (PO-CL) reactions was studiednas a function of time and order of reagent addition. Based on n1nH-NMR analyses, kinetics of UV absorbancenand emission intensity vs. time profiles, we conclude that PO-CL reactions in the presence of imidazole (ImH)ncan proceed by three distinct reaction pathways depending on how the reagents are mixed together. Whennbis(2,4,6-trichlorophenyl) oxalate (TCPO) is mixed simultaneously with H2O2, ImH and perylene, a slowlyndecaying emission curve is generated from the interaction between perylene and a high-energy intermediaten(i.e., six- or eight-membered cyclic compound) formed by the ImH-catalyzed nucleophilic reaction (TCPO-CLnreaction). Upon mixing TCPO simultaneously with ImH and perylene in the absence of H2O2, however, distinctlyndifferent CL curves of lower intensity are generated from the interaction between perylene and a new, unknownnhigh-energy intermediate formed from the reaction between the aryl oxalate and ImH. Finally, using n1nH-NMR,nwe observed that 1,1u0001-oxalyldiimidazole (ODI) is also formed from the reaction between TCPO and ImH. WhennODI reacts with excess H2O2 in the presence of perylene, a higher intensity and relatively fast decaying emissionncurve is generated (ODI-CL reaction) from the interaction between perylene and the high-energy intermediatenproduced, which we propose is imidazolylhydroxydioxetanone or 1,2-dioxetanedione.