Spectrochemistry and artificial color modulation of Cypridina luminescence: indirect evidence for chemiexcitation of a neutral dioxetanone and emission from a neutral amide

Naumov, Panče; Wu, Chun; Liu, Ya Jun; Ohmiya, Yoshihiro

doi:10.1039/c2pp25020a

Cited by 33 publications

(46 citation statements)

References 31 publications

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“…This led these authors to propose that in these chemiluminescent systems, chemiexcitation results from the decomposition of a neutral dioxetanone and not from an anionic one (Scheme ). “Neutral” chemiexcitation is not unheard‐of, as there is in the literature both experimental and theoretical indirect evidence for this type of process in firefly and Cypridina bioluminescence …”

Section: Introductionmentioning

confidence: 90%

Interstate Crossing-Induced Chemiexcitation Mechanism as the Basis for Imidazopyrazinone Bioluminescence

2016

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Imidazopyrazinone dioxetanone is a central molecule in bioluminescence, as it is the scaffold responsible for light emission in many marine species. Herein, we have theoretically studied the thermolysis of its neutral and anionic forms. Our results allowed us to explain imidazopyrazinone bioluminescence with the Interstate Crossing‐Induced Chemiexcitation (ICIC) mechanism, and explain why neutral forms emit light efficiently to the contrary of anionic ones. Both forms decompose via a stepwise‐biradical pathway, but the biradical is formed either via an electron transfer (anion) or due to homolytic bond cleavage (neutral species). Absence of electron transfer leads to an entropic trap, a flat region where infinite possibilities for chemiexcitation exist. However, the resulting products can be in either triplet or singlet excited states. The triplet to singlet ratio is determined by the electron spin density distribution, which controls the rates of intersystem crossing.

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Section: Introductionmentioning

confidence: 90%

Interstate Crossing-Induced Chemiexcitation Mechanism as the Basis for Imidazopyrazinone Bioluminescence

2016

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“…The final key functionality is an ionizable group, which can trigger the charge/electron transfer and finely tune the activation energy of the thermal reaction . Such groups are also responsible for modulating the color of light emitted by the CL/BL product …”

Section: Structural Similarities In Bioluminescence Substratesmentioning

confidence: 99%

Chemiluminescence and Bioluminescence as an Excitation Source in the Photodynamic Therapy of Cancer: A Critical Review

2016

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Photodynamic therapy (PDT) of cancer is known for its limited number of side effects, and requires light, oxygen and photosensitizer. However, PDT is limited by poor penetration of light into deeply localized tissues, and the use of external light sources is required. Thus, researchers have been studying ways to improve the effectiveness of this phototherapy and expand it for the treatment of the deepest cancers, by using chemiluminescent or bioluminescent formulations to excite the photosensitizer by intracellular generation of light. The aim of this Minireview is to give a précis of the most important general chemi-/bioluminescence mechanisms and to analyze several studies that apply them for PDT. These studies have demonstrated the potential of utilizing chemi-/bioluminescence as excitation source in the PDT of cancer, besides combining new approaches to overcome the limitations of this mode of treatment.

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“…These conclusions have been supported by experimental studies on imidazopyrazinones and other systems . Indirect experimental data obtained from both Cypridina and the firefly systems also indicate that efficient chemiexcitation is caused by the thermolysis of neutral dioxetanones . Thus, it appears that ionizable groups are not required for efficient chemiexcitation.…”

Section: Introductionmentioning

confidence: 99%

“…In most chemiluminescent and bioluminescent systems, light is generated via a similar two‐step mechanism: the oxidation of the substrate, with production of an unstable and energy‐rich cyclic peroxide intermediate (Scheme ); and the subsequent thermolysis of the peroxide intermediate, which allows for a thermally activated singlet ground state ( S 0 ) reaction to produce an oxidized reaction product in first singlet excited state ( S 1 ) (Scheme ) . Chemiexcitation can also lead to generation of products in their first triplet state ( T 1 ).…”

Section: Introductionmentioning

confidence: 99%

Mechanistic insights into the efficient intramolecular chemiexcitation of dioxetanones from TD‐DFT and multireference calculations

Silva

Magalhães

2018

Int J of Quantum Chemistry

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Despite decades of research, it is still not clear what is the mechanism behind the efficient chemiexcitation of dioxetanones in chemiluminescent and bioluminescent reactions. In fact, long‐standing theories (charge transfer‐initiated luminescence and chemically induced electron‐exchange luminescence) have been demonstrated to not be able to explain this phenomenon. Herein, a theoretical approach using reliable and up‐to‐date methodology was used to address this problem, by focusing on model dioxetanones. Time‐dependent (TD)‐Density functional theory (DFT) and multireference complete‐active‐space second‐order perturbation theory (CASPT2) calculations provided evidence that points to efficient intramolecular chemiexcitation being the result of the reacting molecules having access to a long zone of the Potential energy surface (PES), within the biradicalar region, where S0 and S1 are degenerate. Molecules with inefficient chemiexcitation are unable to reach this zone of degeneracy. Our main finding is that access to the region of degeneracy appears to be given due to increased interaction between the keto and CO2 moieties, as supported by the use of the activation strain model and Born‐Oppenheimer molecular dynamics, which extends the biradical region by delaying the rupture of the peroxide ring. Increased interaction derives from attractive electrostatic interactions between the moieties of dioxetanone. Thus, we hypothesize that efficient chemiexcitation results not only from electron/charge transfer and subsequent charge annihilation but is instead based on the degree of interaction between the keto and CO2 moieties, which controls the access to a region of degeneracy between the ground and excited states.

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Spectrochemistry and artificial color modulation of Cypridina luminescence: indirect evidence for chemiexcitation of a neutral dioxetanone and emission from a neutral amide

Cited by 33 publications

References 31 publications

Interstate Crossing-Induced Chemiexcitation Mechanism as the Basis for Imidazopyrazinone Bioluminescence

Interstate Crossing-Induced Chemiexcitation Mechanism as the Basis for Imidazopyrazinone Bioluminescence

Chemiluminescence and Bioluminescence as an Excitation Source in the Photodynamic Therapy of Cancer: A Critical Review

Mechanistic insights into the efficient intramolecular chemiexcitation of dioxetanones from TD‐DFT and multireference calculations

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