POLARIZATION SPECTRA OF FREE BASE TETRAPHENYLPORPHYRIN AND ITS ZN-METALLO, CU-METALLO COMPLEXES

Polarized absorption and linear dichroism (LD) spectra of free base tetraphenylporphyrin (H2TPP) and its Zn, Cu complexes are reported using polyethylene, polypropylene films and liquid crystals as orienting matrices. No out-of-plane polarization was found in the range 300 nm < λ < 700 nm for any porphyrin derivatives studied in the liquid crystal phase. In contrast a distinct negative LD at about 400 nm for H2TPP as well as for its metallo complexes ZnTPP and CuTPP in stretched polymer foils indicates an out-of-plane transition caused by interactions with the host matrix. This transition has been attributed to a vibronic satellite of an electric-dipole forbidden 1(π,π*) state located in the Soret region. Changes of the polarization in the visible region are interpreted by vibronic coupling with the polymer foil. At low temperatures (5 K) a splitting of the Soret and Q(0,0) transitions of partially oriented ZnTPP was observed in polypropylene foils. At this temperature the Q(0,1) band of ZnTPP appeared as a superposition of at least eight broad transitions. © 1979.