Chemiluminescence mechanism

The theoretical yield is approached by the firefly reaction, discussed later, which is reported to have of 88% (5). In practice, however, most chemiluminescent reactions are inefficient, withQc values on the order of 1% or much less. The factors influencing yields can be discussed in terms of a generalized three-step chemiluminescent mechanism (6) ... 

Tertiary peroxyl radicals also produce chemiluminescence although with lower efficiencies. For example, the intensity from cumene autooxidation, where the peroxyl radical is tertiary, is a factor of 10 less than that from ethylbenzene (132). The chemiluminescent mechanism for cumene may be the same as for secondary hydrocarbons because methylperoxy radical combination is involved in the termination step. The primary methylperoxyl radical terminates according to the chemiluminescent reaction just shown for (36), ie, R = H. 

Figure 8 Chemiluminescent mechanism for 1,2-dioxetanes (A) a concerted decomposition process (B) a two-step biradical process.

Figure 12 Proposed chemiluminescent mechanism for Schiff bases.

SCHEME 4. Chemiluminescence mechanism of an oxalic acid derivative in the presence of H2O2... 

The main features of the chemiluminescence mechanism are exemplarily illustrated in Scheme 11 for the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of imidazole (IMI-H) as base catalyst and the chemiluminescent activators (ACT) anthracene, 9,10-diphenylanthracene, 2,5-diphenyloxazole, perylene and rubrene. In this mechanism, the replacement of the phenolic substituents in TCPO by IMI-H constitutes the slow step, whereas the nucleophilic attack of hydrogen peroxide on the intermediary l,l -oxalyl diimidazole (ODI) is fast. This rate difference is manifested by a two-exponential behavior of the chemiluminescence kinetics. The observed dependence of the chemiexcitation yield on the electrochemical characteristics of the activator has been rationalized in terms of the intermolecular CIEEL mechanism (Scheme 12), in which the free-energy balance for the electron back-transfer (BET) determines whether the singlet-excited activator, the species responsible for the light emission, is formed ... 

Analogously to the firefly luciferin/luciferase system, the general chemiluminescence mechanism postulated for 9-carboxyacridinium derivatives proposes the 1,2-dioxetanone 45 as high-energy intermediate However, this 1,2-dioxetanone is the only intermediate that has not yet been isolated . The cleavage of the peroxidic ring presumably results in the release of CO2 and the formation of an acridan residue in its electronically excited state (Scheme 32). 

Luminescent bacteria are found in various ecological niches, but most species are present in the ocean where some live in symbiosis with fish. Light emission can be switched on and off and it is the present thesis that bacterial bioluminescence goes by a sensitized chemiluminescence mechanism luminescent bacteria are placed into two genera, Vibrio and... 

A review of chemiluminescent and bioluminescent methods in analytical chemistry has been given by Kricka and Thorpe. A two-phase flow cell for chemiluminescence and bioluminescencc has been designed by Mullin and Seitz. The chemiluminescence mechanisms of cyclic hydrazides, such as luminol, have been extensively analysed. " Fluorescence quantum yields of some phenyl and phenylethynyl aromatic compounds in peroxylate systems have been determined in benzene. Excited triplet states from dismutation of geminate alkoxyl radical pairs are involved in chemiluminescence from hyponitrite esters. Ruorophor-labelled compounds can be determined by a method based on peroxyoxalate-induced chemiluminescence. Fluorescence and phosphorescence spectra of firefly have been used to identify the multiplicity of the emitting species. " The chemiluminescence and e.s.r. of plasma-irradiated saccharides and the relationship between lyoluminescence and radical reaction rate constants have also been investigated. Electroluminescence from poly(vinylcarbazole) films has been reported in a series of four... 

Several additional chemiluminescence mechanisms have been described, which are based on excited-state generation by electron transfer in a radical ion pair according to... 

DEVELOPMENT OF THE CHEMISTRY OF THE IMIDAZOPYRAZIONONE-BIOLUMINESCENCE SYSTEM FROM THE BIO- AND CHEMILUMINESCENCE MECHANISM TO A DESIGN OF SENSOR MOLECULES... 

STUDIES ON THE CHEMILUMINESCENCE MECHANISM OF CYPRIDINA LUCEFERIN ANALOGUES DISSOCIATION CONSTANTS OFTHE SINGLET-EXCITED CYPRIDINA OXYLUCEFERIN ANALOGUES... 

Scheme 1. Postulated chemiluminescence mechanism for Cypridina luciferin analogue (CLA) and its derivatives. The parentheses donate possible protonations.

Thompson A, Canella KA, Lever JR, Miura K, Posner GH, Seliger HH. Chemiluminescence mechanism and quantum yield of synthetic vinylpyrene analogs of benzo[a]pyrene-7,8-dihydrodiol. J Am Chem Soc 1986 108 4498-504. 

Lind J, Merenyi G, Eriksen TE. Chemiluminescence mechanism of cyclic hydrazides such as luminol in aqueous solutions. J Am Chem Soc 1983 105 7655-61. 

The data in Table I reveal a trend towards higher Ea values with increasing extent of singlet oxygenation or time of autoxidation. A possible interpretation of this observation may be sought in a consideration of the autoxidation-chemiluminescence mechanism (1-17). Since the rate... 

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