Mechanistic insights in charge-transfer-induced luminescence of 1,2-dioxetanones with a substituent of low oxidation potential

Hiroshi Isobe, Yu Takano, Mitsutaka Okumura, Seiki Kuramitsu, Kizashi Yamaguchi

Research output: Contribution to journalArticlepeer-review

85 Citations (Scopus)

Abstract

We have investigated the decomposition pathway of dioxetanones 1c with a phenoxide anion group by the B3LYP/6-31+G(d) method together with the second-order multireference Moller-Plesset perturbation (MRMP) theory and propose charge-transfer-induced luminescence (CTIL) with polarization-induced branching excitation processes. In the gas phase, the thermal decomposition of 1c occurs by an asynchronous two-stage pathway without a discrete intermediate; that is, the initial O-O bond breaking to generate a charge-transfer (CT) diradical species is immediately followed by the subsequent C-C bond breaking with simultaneous back CT, which is responsible for the surface crossing at the avoided crossing. The activation energy is dramatically reduced from 19.4 to 3.8 kcal mol-1 by the deprotonation of phenol meta-1d to its anion meta-1c, showing an important role of the endothermic CT. The odd/even selection rule for the chemiluminescence efficiency can be explained by the orbital interaction for the back CT between the carbonyl π* orbital and either a HOMO or a LUMO of the generated light emitters. To examine the accessibility of the chemically initiated electron exchange luminescence (CIEEL) route, we considered the solvent effects on the free-energy change of meta-1c by using continuum solvent models. The bending vibration mode of the CO2 fragment is specifically considered. Borderline features emerges from the solution-phase CT reaction of meta-1c, which depends on the solvent polarity: one is a nonadiabatic or adiabatic back CT process (polarization-induced concerted CTIL), and the other is a radical dissociation, i.e., complete one-electron-transfer process (CIEEL).

Original languageEnglish
Pages (from-to)8667-8679
Number of pages13
JournalJournal of the American Chemical Society
Volume127
Issue number24
DOIs
Publication statusPublished - Jun 22 2005
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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