ELECTRONIC SPECTRA OF SINGLE CRYSTALS OF FREE BASE PORPHYRIN

Abstract

Polarized absorption spectra of free base tetraphenylporphin single crystals from the near it to the uv have been obtained with a recording microspectrophotometer on crystals grown between microscope cover slips. The crystals are triclinic with one molecule per unit cell. The porphyrin planes are stacked perpendicular to the viewing face, resulting in a polarization ratio of 170 between the in-plane and out-of-plane polarized spectra. The bands are not appreciably broadened relative to the solution spectrum; the Soret appears normal”, although red-shifted by $1500 cm^{-1}$. An out-of-plane polarized transition has been discovered at $27 000 cm^{-1}$ (371 nm).