Mechanistic study of the unimolecular decomposition of 1,2-dioxetanedione

Three S0/S1 Conical Intersections Control Electron-Transfer-Catalyzed Chemiluminescence of 1,2-Dioxetanedione

Chemiluminescence (CL) utilizing four-membered cyclic peroxides is one of the most useful analytical techniques. Up to now, the CL mechanisms for nonketone (1,2-dioxetanes) and monoketone (1,2-dioxetanones) derivatives of four-membered cyclic peroxides have been intensively studied experimentally and theoretically in the past several decades, but no general mechanism has been concluded to rationalize the origin of high-efficiency singlet chemiexcitation. In contrast, as the only diketone derivative of four-membered cyclic peroxide, the electron-transfer (ET)-catalyzed CL of 1,2-dioxetanedione (DDO), which is most suggested as a critical step in the well-known peroxyoxalate CL (POCL), has never been theoretically investigated and uncovered yet. In this work, we theoretically investigated the rubrene-catalyzed decomposition of DDO for the first time, with a hybrid quantum mechanical/molecular mechanical model and nonadiabatic molecular dynamics simulation. The computation shows a stepwise ET-catalyzed decomposition and three S₀/S₁ conical intersection (CI)-controlled singlet chemiexcitation. The three universal S₀/S₁ CIs play different roles in the high-efficiency singlet chemiexcitation in ET-catalyzed CL of DDO and should be the true origin of the high-efficiency singlet CL. We believe that the current work could not only provide a further understanding for high-efficiency singlet CL but also provide some general clues to designed new high-efficient CL systems.

Recent Advances in Self-Exciting Photodynamic Therapy

Photodynamic therapy (PDT) is already (Food and Drug Administration) FDA approved and used in the clinic for oncological treatment of pancreatic, lung, esophagus, bile duct, and of course several cancers of skin. It is an important tool in the oncological array of treatments, but for it exist several shortcomings, the most prominent of which is the shallow depth penetration of light within tissues. One-way researchers have attempted to circumvent this is through the creation of self-exciting "auto-PDT" nanoplatforms, which do not require the presence of an external light source to drive the PDT process. Instead, these platforms are driven either through oxidative chemical excitation in the form of chemiluminescence or radiological excitation from beta-emitting isotopes in the form of Cherenkov luminescence. In both, electronic excitations are generated and then transferred to the photosensitizer (PS) via Resonance Energy Transfer (RET) or Cherenkov Radiation Energy Transfer (CRET). Self-driven PDT has many components, so in this review, using contemporary examples from literature, we will breakdown the important concepts, strategies, and rationale behind the design of these self-propagating PDT nanoplatforms and critically review the aspects which make them successful and different from conventional PDT. Particular focus is given to the mechanisms of excitation and the different methods of transfer of excited electronic energy to the photosensitizer as well as the resulting therapeutic effect. The papers reviewed herein will be critiqued for their apparent therapeutic efficiency, and a basic rationale will be developed for what qualities are necessary to constitute an "effective" auto-PDT platform. This review will take a biomaterial engineering approach to the review of the auto-PDT platforms and the intended audience includes researchers in the field looking for a new perspective on PDT nanoplatforms as well as other material scientists and engineers looking to understand the mechanisms and relations between different parts of the complex "auto-PDT" system.

Theoretical Analysis of the Effect Provoked by Bromine-Addition on the Thermolysis and Chemiexcitation of a Model Dioxetanone

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.

Theoretical modulation of singlet/triplet chemiexcitation of chemiluminescent imidazopyrazinone dioxetanone via C8-substitution

DFT analysis of the thermolysis of C₈-substituted imidazopyrazinone dioxetanone allows the rational tuning of the activation barrier and singlet/triplet chemiexcitation.

A combined theoretical and experimental study on the mechanism of spiro-adamantyl-1,2-dioxetanone decomposition

Our study on the unimolecular decomposition of a relatively stable 1,2-dioxetanone derivative, model compound for bioluminescence processes, indicates the existence of different reaction pathways for ground and excited state formation.