SOL-GEL HOSTS DOPED WITH PORPHYRIN DERIVATIVES .1. SPECTROSCOPY, HOLE-BURNING AND SPECTRAL DIFFUSION

Pure inorganic sol-gel matrices as well as hybrid organic/inorganic xe rogels have been doped with porphyrins derivatives and studied using l ine narrowing techniques, The role of residual hydroxyl groups is inve stigated, Free-base porphyrins are protonated in pure inorganic hosts, but the matrix acidity is reduced in hybrid matrices or when fluorina ted porphyrins derivatives are used. The linear electron-phonon coupli ng can be controlled with the choice of the organic group in organic/i norganic matrices. Persistent spectral hole widths increase with tempe rature according a glass-like T-n dependence and evidence of spectral diffusion is shown in one of these systems.