Solvent polarity influence on chemiexcitation efficiency of inter and intramolecular electron-transfer catalyzed chemiluminescence

The Molecular Basis of Organic Chemiluminescence

“…Theoretical studies on the rubrene-catalyzed decomposition of 1,2-dioxetanedione indicated the occurrence of a stepwise electron-transfer and electron back-transfer mechanism including various S 0 /S 1 conical intersections in the different electron-transfer states, which could lead to chemiexcitation of the activator [ 39 , 62 ]. This approach allowed it to estimate a singlet excitation quantum yield of around 50%, in reasonable agreement with experimental data for different conditions [ 3 , 4 , 11 , 58 , 59 , 60 ].…”

“…Additionally, it has been shown that the low efficiency of the processes is not due to the cage-escape of radical ion pairs by experimental studies of the solvent viscosity effect on the singlet quantum yield using different solvent mixtures and intermolecular CIEEL systems [ 55 , 56 , 57 , 58 ]. A detailed study of the solvent polarity influence on the chemiexcitation efficiency of intermolecular CIEEL systems in different binary polar aprotic and nonpolar solvent systems has shown that an optimum polarity for efficient chemiexcitation exists; however, the polarity influence on the quantum yields is relatively low, indicating low charge separation in the chemiexcitation sequence and favoring the occurrence of a charge transfer, not a complete electron transfer in this mechanism [ 59 ]. Contrarily to the inefficient CIEEL systems discussed above, the peroxyoxalate reaction constitutes an intermolecular electron-transfer catalyzed system with verified high quantum yields that can reach close to 100% in optimal conditions [ 3 , 4 , 11 , 58 , 59 , 60 ].…”

“…This conclusion of an entirely intramolecular transformation in the induced decomposition of phenoxy-substituted 1,2-dioxetanes has been further sustained by studies on the solvent viscosity effects on several inter- and intramolecular CIEEL systems, whose results could be justified by an intramolecular electron back-transfer step in the induced 1,2-dioxetane decomposition [ 55 , 56 , 57 ]. Additionally, a most recent study of the solvent polarity effect on the chemiexcitation efficiency of inter- and intramolecular CIEEL chemiexcitation systems, including catalyzed 1,2-dioxetanone decomposition, and induced 1,2-dioxetane decomposition indicated that in the latter transformation, the electron back-transfer should occur in an intramolecular fashion, whereas in the former, this process should be intermolecular [ 59 ].…”

Combined Experimental and Theoretical Investigation into the Photophysical Properties of Halogenated Coelenteramide Analogs

“…BL is widespread in nature and can be found in organisms as different as fireflies, jellyfishes, bacteria, and fungi, among others [1][2][3][4]. Typically, light emission from CL/BL reactions originates due to the formation of a high-energy peroxide intermediate, which decomposes rather quickly with high exothermicity, which allows for chemiexcitation to excited states [5][6][7][8][9][10].…”

Exploring the Structural Space of Chemiluminescent 1,2-Dioxetanes

“…Because the reaction is initiated by an electron transfer (or possibly charge transfer) from an electron-rich donor to a peroxide acceptor, Schaap and co-workers were able to develop a 1,2-dioxetane linked to a phenolate that could undergo an intramolecular CIEEL mechanism. − This mechanism proceeds via an electron transfer from the phenolate to the 1,2-dioxetane, followed by bond cleavage, and then another back electron transfer to form the singlet excited state of the phenolate, which emits a photon of light (Scheme ). Intramolecular and intermolecular back electron transfer steps, , as well as other mechanisms like charge transfer induced luminescence (CTIL), wherein partial charge transfer from the phenolate to the peroxide bond is thought to occur as opposed to the full transfer and generation of radical ion pairs assumed in CIEEL, have been proposed . Importantly, chemiluminescence emission via a CIEEL mechanism can be triggered by masking the phenolate with a protecting group that is only deprotected in the presence of an analyte.…”