Porphyrin free base phosphorescence
Abstract
The wavelength for heavy atom enhanced phosphorescence is unambiguously established by time resolved excitation spectra in 50% EPA and 50% ethyl iodide at 77 K for protoporphyrin (795 nm), mesoporphyrin (773 nm), octaethylporphin (768 nm), and porphin (785 nm). Excitation spectra also establish the phosphorescence wavelength of brominated protoporphyrin in EPA at 77 K to be 783 nm, with a quantum yield φp ∼ 9 × 10 -4. Using laser excitation the phosphorescence quantum yields in EPA were found for protoporphyrin ( φp ∼ 5 × 10 -5), mesoporphyrin ( φp < 6 × 10 -5), and tetraphenylprophin ( φp ∼ 2 × 10 -5). Tetraphenylporphin phosphorescence shows no heavy atom enhancement. Natural radiative lifetimes for phosphorescence of the various free bases are found to be 70 sec and higher.
- Publication:
-
Journal of Molecular Spectroscopy
- Pub Date:
- October 1974
- DOI:
- 10.1016/0022-2852(74)90263-X
- Bibcode:
- 1974JMoSp..53...88G