Chemically Initiated Electron Exchange intramolecular

Chemically Initiated Electron Exchange Luminescence (CIEEL) acridinium salts, 1256 alkaline phosphatase, 1193-8 1,2-dioxetanes, 1182-200 firefly bioluminescence, 1191-3 intermolecular, 1213-15, 1231-6 intramolecular, 1214-15, 1236-8 luminol, 1247-8... 

The mechanism of chemically initiated electron exchange luminescence (CIEEL) has been specified and studied in solvents of different viscosities [226-230]. The intramolecular electron transfer in the oxyaryl-substituted adamantyldioxetane anion D [2 (the boldfaced numbers refer to the numbered structures 1-5 in Fig. 3.77)], followed by decomposition of the latter into two radicals A and M (5), allows them to diffuse freely in and out of the cage until the backward electron transfer (BET) excites the methyl-m-oxybenzoate anion M (4), as shown in Figure 3.77. In general, the intermolecular BET mechanism of excitation (right branch) competes with a direct chemiexcitation in the course... 

Adam W, Bronstein I, Trofimov AV, VasiTev RE. Solvent-cage effect (viscosity dependence) as a diagnostic probe for the mechanism of the intramolecular chemically initiated electron-exchange luminescence (CIEEL) triggered from a spiroadamantyl-substituted dioxetane. J Am Chem Soc 1999 121 958-61. 

This was further elaborated upon by Schuster and co-workers (K21, S23, S24) and by Schaap s group at Wayne State University (S6, S8, SIO, Sll, Z2, Z3). Thus, the observation that some hydroxy-substituted aromatic dioxetanes show high chemiluminescent efficiencies at alkaline pH (phenolic anionic form) led to the formulation of a third mechanism for chemiluminescent decomposition of dioxetanes. This mechanism, known initially as intramolecular electron transfer (Ml9, Z2) and subsequently as chemically initiated electron exchange luminescence, or CIEEL (FI, K20), can be best illustrated by reference to the dioxetane shown in Fig. 37, where the chemiluminescence is triggered by the addition of fluoride ions. 

The E-diethylstilbestrol-4 ,4 -semiquinone oxygen-centred radical is converted to a carbon centred radical which reacts with Oj forming a di-oxetane. Unless the dioxetane is rapidly protonated, it will almost instantly cleave into excited carbonyl products because of the intramolecular chemically initiated electron exchange luminescence. In the latter, electron transfer from the phenoxide moiety to the peroxide ring promotes the fluorescence observed from the singlet-excited 4-hydroxy propio-... 

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