Fluorescence of 2,3-Diazabicyclo[2.2.2]oct-2-ene revisited: solvent-induced quenching of the n,.pi.-Excited state by an aborted hydrogen atom transfer.
- Publication Type
- Journal contribution
- Authors
- Nau, W. M.; Greiner, G.; Rau, H.; Wall, J.; Olivucci, M.; Scaiano, J. C.
- Year of publication
- 1999
- Published in
- J. Phys. Chem. A
- Band/Volume
- 103/11
- ISBN / ISSN / eISSN
- 1089-5639
- Page (from - to)
- 1579-1584
The fluorescence lifetimes of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) were detd. in a large no. of solvents and solvent mixts., displaying variations from 825 ns in CD3CN to 13 ns in CHCl3. Large deuterium isotope effects (8-11) and significant activation energies (generally 2-15 kJ mol-1) for fluorescence quenching of DBO are obsd., which support a novel solvent-induced quenching mechanism via an aborted hydrogen atom transfer. In CCl4 a photoinduced electron-transfer quenching mechanism may compete. The fluorescence quenching by solvent mixts. is not proportional to the mole fraction of the two components, indicating a preferential solvation of the excited state.