Decomposition of dioxetane induced by electron transfer from a photoexcited lanthanide ion

Шарипов, Г. Л.; Ostakhov, S. S.; Ableeva, N. Sh.; Волошин, А. И.; Казаков, В. П.; Толстиков, Г. А.

doi:10.1007/bf00697057

Cited by 3 publications

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“…"rO T = ~0296@T/~ 296, (7) where to T, r T0296, and 6296 are the lifetimes and the quantum yields of luminescence of Ce 3"-* at the given temperature and at 296 K, respectively. The x 0 values at different temperatures and kq (see Table 2), which are lower than the diffusion constants at these temperatures, were calculated from Eq.…”

Section: Resultsmentioning

confidence: 99%

Photocatalytic decomposition of dispiro(diadamantane-1,2-dioxetane) initiated by Ce(CIO4)3 in the excited state

et al. 1997

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Photocatalytic decomposition of dispiro(diadamantane-1,2-dioxetane) (1) to adamantanone (2) initiated by Ce(CIO4) 3 in the excited state in the MeCN--CHCI 3 (2 : 1) mixture was studied. The bimolecular rate constants of quenching kq were determined from the kinetics of quenching of Ce 3** by dioxetane at different temperatures. The Arrhenius parameters of the quenching were calculated from the temperature dependence of kq: E a = 3.2_+.0.3 kcal rap[ -I and logA = I 1.6+0.6. The quantum yields of photolysis of 1 depending on its concentration and the rate constant of the chemical reaction of Ce 3+* with 1 were determined. The latter coincides with kq.: kch = (2.6-L-0.3) -109 L real -I s -t (T = 298 K). The fact that the maximum quantum yield at decomposition of dioxetane is equal to I indicates the absence of physical quenching of Ce 3+* by dioxetane. It is believed that the electron transfer occu~ in the reaction of Ce 3+" with 1. Nonradiative deactivation of Ce 3.* in solutions of MeCN and in MeCN--CHCI 3 mixtures was studied. It is caused by the replacement of HzO molecules in the nearest coordination surroundings of Ce 3+ by solvent molecules and reversible transfer of an electron to the ligand. The activation parameters of the nonradiative deactivation of Ce 3"* were determined.Key words: photocatalysis, quenching, energy transfer, dioxetane, cerium perchlorate. t,2-Dioxetanes (four-membered cyclic peroxides) decompose into carbonyt fragments under the action of UV or IR irradiation, i,z The transfer of excitation energy from a donor to the vibrational terms of dioxetane also favors its decomposition. In these systems, the sensitized decomposition of peroxide can occur with a quantum yield >1. 3,'1 Both polyaromatic promoters 5 and luminescent metal complexes 4,6 can act as sensitizers.The decomposition of dioxetane initiated, e.g., by an excited europium chelate, is caused by the formation of a complex and by the intracomplex transfer of energy from Eu lIX* to dioxetane (Scheme 1). The energy released in the decomposition of dioxetane results in the regeneration of excited Eu II1. and its further participation in the photocatalytic process.Dioxetane also decomposes due to reversible electron transfer, for example, when a Ru 11 trisdipyridyl complex is irradiated in solution (Scheme 2). 6Photocatalysis by lanthanides via Scheme 2 is the most probable using Ce 3+, since this ion has the lowest oxidation potential of the lanthanides. The photochemical activity of cerium in the reaction with dioxetane has been previously demonstrated 7 using CeC13 as an example. In the present work, the photodecomposition of dispiro(diadamant ane-1,2-dioxetane)( 1 ) to adamantanone (2) initiated by excited cerium perchlorate (Scheme 3) was studied.

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Section: Resultsmentioning

confidence: 99%