Cyclic Peroxidic Carbon Dioxide Dimer Fuels Peroxyoxalate Chemiluminescence

Abstract

Peroxyoxalate chemiluminescence is used in selfcontained light sources, such as glow sticks, where oxidation of aromatic oxalate esters produces a high-energy intermediate (HEI) that excites fluorescence dyes via electron transfer chemistry, mimicking bioluminescence for efficient chemical energy-to-light conversion. The identity of the HEI and reasons for the efficiency of the peroxyoxalate reaction remain elusive. We present here unequivocal proof that the HEI of the peroxyoxalate system is a cyclic peroxidic carbon dioxide dimer, namely, 1,2-dioxetanedione. Oxalic peracids bearing a substituted phenyl group were unable to directly excite fluorescent dyes; hence, they could be ruled out as the HEI. However, base-catalyzed cyclization of these species results in bright chemiluminescence, with decay rates and chemiexcitation quantum yields that are influenced by the electronic phenylic substituent properties. Hammett (ρ = +2.2 ± 0.1) and Brønsted (β = −1.1 ± 0.1) constants for the cyclization step preceding chemiexcitation imply that the loss of the phenolateleaving group and intramolecular nucleophilic attack of the percarboxylate anion occur in a concerted manner, generating 1,2dioxetanedione as the unique outcome. The presence of better leaving groups influences the reaction mechanism, favoring the chemiluminescent reaction pathway over the nonemissive formation of aryl-1,2-dioxetanones.

The Molecular Basis of Organic Chemiluminescence

“…The extremely unstable unsubstituted 1,2-dioxetane has been synthesized and characterized by Adam and Baader [ 10 ]; however, the unsubstituted 1,2-dioxetanone has never been obtained, supposedly due to its higher instability. The last member of the trinity of four-membered ring peroxides essential for CL is the elusive 1,2-dioxetanedione ( 3 ), which was postulated long ago as the HEI in the peroxyoxalate reaction [ 11 , 12 , 13 , 14 ], a hypothesis that has been supported by recently available experimental data [ 15 ].…”

An Update on General Chemiexcitation Mechanisms in Cyclic Organic Peroxide Decomposition and the Chemiluminescent Peroxyoxalate Reaction in Aqueous Media†

“…The structure of the high-energy intermediate has been in discussion during the years (15); after the initial suggestion of the Rauhut group of 1,2-dioxetanedione (7), several other structural proposals for the HEI have been made, including diverse cyclic peroxides and peracid derivatives (15)(16)(17)(18)(19)22,68,69). However, as already mentioned above, recent Hammett studies have given direct evidence on 1,2-dioxetanedione (3) as the structure of the high-energy intermediate in the peroxyoxalate system (21). It has also been shown that the chemiexcitation mechanism of the peroxyoxalate reaction involves a rate-limiting electron or charge transfer, where the electronically excited state of the ACT is formed by its interaction with the HEI (41,42,44,45).…”

“…The third member of the fourmembered cyclic peroxide family, 1,2-dioxetanedione (3) (Fig. 1), has been early postulated as the high-energy intermediate in the peroxyoxalate reaction (7), and evidence for its real existence accumulated during subsequent years (15)(16)(17)(18)(19)(20), including quite recent direct evidence from Hammett studies on peracid derivatives (21).…”

A novel enzyme-free long-lasting chemiluminescence system based on a luminol functionalized β-cyclodextrin hydrogel for sensitive detection of H2O2 in urine and cells

“…The bacterial bioluminescence system, firefly bioluminescence system and peroxidase-luminol CL system are typical CL systems with the participation of enzymes. 7,8 However, the inactivation of enzymes is the major reason for the decrease of CL intensity. The peroxyoxalate ester CL system can generate long-lasting CL emission without the involvement of an enzyme, and has been applied in daily products, such as fishing lures and glow sticks.…”