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2-Coumaranones are evolving as a new, efficient, versatile, and synthetically accessible platform for the next generation chemiluminescent probes. Despite the favorable quantum yields, the exact mechanism of their chemiluminescence remains elusive. Here, we analyze the details of the mechanism of the 2-coumaranone chemiluminescence using a combination of experimental and computational methods. By using EPR spectroscopy we show that superoxide radical anions are involved in the reactions, in support of the hypothesis that the mechanism includes a single electron transfer step. The decomposition of the high-energy intermediate, 1,2-dioxetanone, is described in the ground state and in the first three excited singlet states, and indicates that there is at least one conical intersection, which is crucial for generation of excited-state molecules. A peroxy anion that is generated was found to be able to undergo a side reaction that leads to the same (isolated) product as in the light-generating reaction. These results demonstrate the applicability of 2-coumaranones as a model system for several bioluminescence reactions and may lead to the design of new 2-coumaranone derivatives with superior emission characteristics for bioanalytical applications. [ABSTRACT FROM AUTHOR]

The bioluminescence reaction of many biological subspecies, most notably fireflies, forms dioxetanone derivatives as high-energy intermediates. The thermal instability of dioxetanones complicates understanding of the transition from the ground state to the first excited state that leads to light emission. Herein, we report the reaction mechanism of 2-coumaranones, synthetically accessible strongly chemiluminescent materials that mimic the bioluminescence reaction. The pathways of chemiexcitation and photorelaxation are clarified on the basis of synthetic evidence and spectrochemical as well as computational mechanistic analysis. [ABSTRACT FROM AUTHOR]

The optimized one-pot synthesis of 16 new 2-coumaranones containing a carbamate side-chain is described. Furthermore, the quantum yields for the base-activated chemiluminescence in the presence of oxygen was determined for all compounds, with a maximum of 5.9 ± 0.1 x 10-2 E mol-1, and the application of these compounds as substitutes for usual bioluminescent and chemiluminescent reagents in bioassays is anticipated. A preliminary mechanistic pathway is also suggested, making use of recent developments regarding aspects of organic chemiluminescence, in agreement with both experimental and theoretical data available on the induced 1,2-dioxetanone decomposition as well as with the high efficiency of this reaction. [ABSTRACT FROM AUTHOR]