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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 mechanism of the chemiluminescent reaction of ethyl (5-fluoro-2-oxo-2,3-dihydrobenzofuran-3-yl) carbamate (a 2-coumaranone derivative) with a base and molecular oxygen was investigated. New evidence from the reaction kinetics and absorption/emission profiles was obtained, supporting the existence of a 1,2-dioxetanone as an intermediate: (i) its characteristic activation parameters (ΔH≠ = 7.2 ± 0.1 kcal mol−1; ΔS≠ = −45 ± 5 cal K−1 mol−1) indicating a high degree of thermal instability and (ii) its bimolecular decomposition rate constant for the reaction with perylene. The newly developed methodology has been shown to be suitable for determining the reactivity of such thermally unstable peroxides, which are very difficult to prepare and isolate, using this alternative approach of in situ generation of a 1,2-dioxetanone. [ABSTRACT FROM AUTHOR]

The conversion of red excitation light into blue emission light (uphill energy conversion) using unstable 1,2-dioxetanes is described. The method is based on 1,2-dioxetane formation by red-light sensitized photooxygenation of adequate alkenes and subsequent blue-light emission due to thermal 1,2-dioxetane cleavage. The energy gain resulting from the chemical energy obtained in the transformation of an alkene into two carbonyl compounds transforms a red-light excitation laser beam into a blue-light chemiluminescence emission, producing thereby a formal anti-Stokes shift of 200–250 nm, opening up a whole spectrum of possible applications. [ABSTRACT FROM AUTHOR]