ChemInform Abstract: CYCLIC PEROXIDES. 81. FLUORESCER‐ENHANCED CHEMILUMINESCENCE OF α‐PEROXYLACTONES VIA ELECTRON EXCHANGE

Photochem & Photobiology

et al. 2013

109

135

Although the mechanisms of many chemiluminescence (CL) reactions have been intensively studied, no general model has been suggested to rationalize the efficiency of these transformations. To contribute to this task, we report here quantum yields for some well-characterized CL reactions, concentrating on recent reports of efficient transformations. Initially, a short review on the most important general CL mechanisms is given, including unimolecular peroxide decomposition, electrogenerated CL, as well as the intermolecular and intramolecular catalyzed decomposition of peroxides. Thereafter, quantum yield values for several CL transformations are compiled, including the unimolecular decomposition of 1,2-dioxetanes and 1,2-dioxetanones, the catalyzed decomposition of appropriate peroxides and the induced decomposition of properly substituted 1,2-dioxetane derivatives. Finally, some representative examples of quantum yields for complex CL transformations, like luminol oxidation and the peroxyoxalate reaction, in different experimental conditions are given. This quantum yield compilation indicates that CL transformations involving electron transfer steps can occur with high efficiency in general only if the electron transfer is of intramolecular nature, with the intermolecular processes being commonly inefficient. A notable exception to this general rule is the peroxyoxalate reaction which, also constituting an example of an intermolecular electron transfer system, possesses very high quantum yields.

Section: General Mechanisms For Excited State Generationmentioning

confidence: 50%

Section: General Mechanisms For Excited State Generationmentioning

confidence: 99%

Section: General Mechanisms For Excited State Generationmentioning

confidence: 99%

Section: General Mechanisms For Excited State Generationmentioning

confidence: 99%

See 2 more Smart Citations

Efficiency of Electron Transfer Initiated Chemiluminescence

Augusto

Photochem & Photobiology

et al. 2013

109

135

“…In some cases this is due to a high triplet/singlet ratio, a limitation that can be overcome using appropriate energy acceptors which can enhance the overall chemiluminescence emission . There are two well distinct mechanisms which can lead to CL emission enhancement: (1) energy transfer from the excited product formed in the reaction to the energy acceptor; (2) direct interaction of the added energy acceptor, now called activator (ACT), with the peroxide (not with the excited reaction product) by a complex electron‐transfer mechanism, known as chemically initiated electron exchange luminescence (CIEEL), first described by Schuster for the catalyzed diphenoyl peroxide ( 1 , Scheme ) decomposition and used to explain the light emission from α ‐peroxylactones ( 2 ) and some 1,2‐dioxetanes ( 3 ) . In these cases, the intramolecular ( 3 and 4 ) transformations are remarkably more efficient than the intermolecular ( 1 and 2 ) ones .…”

Section: Introductionmentioning

confidence: 99%

Chemiexcitation Efficiency of Intermolecular Electron‐transfer Catalyzed Peroxide Decomposition Shows Low Sensitivity to Solvent‐cavity Effects

Khalid

Photochem & Photobiology

Bartoloni

et al. 2016

Intermolecular chemically initiated electron exchange luminescence (CIEEL) systems are known to possess low chemiluminescence efficiency; whereas, the corresponding intramolecular transformations are highly efficient. As the reasons for this discrepancy are not known, we report in this work our studies of the solvent-cavity effect on the efficiency of two intermolecular CIEEL systems, the catalyzed decomposition of diphenoyl peroxide and of a relatively stable 1,2-dioxetanone derivative, spiro-adamantyl-1,2-dioxetanone. The results indicate a very low medium viscosity effect on the quantum yields of these systems, a priori not compatible with these bimolecular transformations, showing also that their low efficiency cannot be due to solvent-cavity escape of intermediate radical ion pairs. In addition, the solvent-cage effect on the CIEEL efficiency, after the occurrence of the initial electron transfer, proved also to be very low, indicating the intrinsic low viscosity effect on the chemiexcitation step. Therefore, it is concluded that the low efficiency of these systems is intrinsic to the chemiexcitation step and cannot be improved by medium viscosity effects, being possibly due to sterical hindrance on charge-transfer complex formation in the initial step of the CIEEL.

Solvent viscosity influence on the chemiexcitation efficiency of inter and intramolecular chemiluminescence systems

Khalid

Photochem Photobiol Sci

Ciscato

et al. 2015

The effects of the medium viscosity on the chemiexcitation quantum yields of the induced decomposition of 1,2-dioxetanes (highly efficient intramolecular CIEEL system) and the catalyzed decomposition of diphenoyl peroxide and a 1,2-dioxetanone derivative (model systems for the intermolecular CIEEL mechanism, despite their low efficiency) are compared in this work. Quantum yields of the rubrene catalyzed decomposition of diphenoyl peroxide and spiro-adamantyl-1,2-dioxetanone as well as the fluoride induced decomposition of a phenoxy-substituted 1,2-dioxetane derivative are shown to depend on the composition of the binary solvent mixture toluene/diphenyl ether, which possess similar polarity parameters but different viscosities. Correlations of the quantum yield data with the medium viscosity using the diffusional and the frictional (free-volume) models indicate that the induced 1,2-dioxetane decomposition indeed occurs by an entirely intramolecular process and the low efficiency of the intermolecular chemiluminescence systems (catalyzed decomposition of diphenoyl peroxide and 1,2-dioxetanone derivative) is not primarily due to the cage escape of radical ion species.