Abstract
Chemi-/bioluminescence are phenomena in which chemical energy is converted into electronically excited singlet states, which decay with light emission. Given this feature, along with high quantum yields and other beneficial characteristics, these systems have gained numerous applications in bioanalysis, in biomedicine, and in the pharmaceutical field. Singlet chemiexcitation is made possible by the formation of cyclic peroxides (as dioxetanones) as thermolysis provides a route for a ground state reaction to produce singlet excited states. However, such thermolysis can also lead to the formation of triplet states. While triplet states are not desired in the typical applications of chemi-/bioluminescence, the efficient production of such states can open the door for the use of these systems as sensitizers in photocatalysis and triplet-triplet annihilation, among other fields. Thus, the goal of this study is to assess the effect of heavy atom addition on the thermolysis and triplet chemiexcitation of a model dioxetanone. Monobromination does not affect the thermolysis reaction but can improve the efficiency of intersystem crossing, depending on the position of monobromination. Addition of bromine atoms to the triplet state reaction product has little effect on its properties, except on its electron affinity, in which monobromination can increase between 3.1 and 8.8 kcal mol−1.
Highlights
Bioluminescence is a widespread natural phenomenon in which living organisms convert chemical energy into light emission via biochemical reactions [1,2,3,4,5]
We started this work by analyzing the thermolysis reaction of unsubstituted dioxetanone IVa and monobrominated species IVb, whose energetic profiles are presented in Figures 1(a) and 1(c), respectively
It should be noted that the iminocyclopentadienyl moiety was based on the scaffold of azaBODIPY [40,41,42], which are molecules capable of producing triplet states upon photoexcitation, when they are functionalized with heavy atoms
Summary
Bioluminescence is a widespread natural phenomenon in which living organisms convert chemical energy into light emission via biochemical reactions [1,2,3,4,5]. Bioluminescence can be found in organisms as different as bacteria, dinoflagellates, fungi, crustaceans, worms, insects, and fishes. Light emission from these systems is the result of enzyme-catalyzed reactions, which can be divided into two main classes: luciferase-luciferin reactions [2, 5,6,7,8] and photoprotein systems [2, 9]. The luciferase enzyme is responsible for catalyzing the oxidation of its substrate, luciferin, which generates an electronically excited singlet state product. This product, generally termed oxyluciferin, subsequently relaxes to the ground state by photon emission. Luciferase-luciferin reactions are the most prevalent bioluminescent systems [1,2,3, 5,6,7,8]
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