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 xerogels have been doped with porphyrins derivatives and studied using line narrowing techniques, The role of residual hydroxyl groups is investigated, Free-base porphyrins are protonated in pure inorganic hosts, but the matrix acidity is reduced in hybrid matrices or when fluorinated porphyrins derivatives are used. The linear electron-phonon coupling can be controlled with the choice of the organic group in organic/inorganic matrices. Persistent spectral hole widths increase with temperature according a glass-like T-n dependence and evidence of spectral diffusion is shown in one of these systems.