  The electronic properties and the molecular orientation of
Zn-tetraphenyl-porphyrin films deposited on Si(111) have been investigated
using synchrotron radiation. For the first time we have revealed and assigned
the fine structures in the electronic spectra related to the HOMOs and LUMOs
states. This is particularly important in order to understand the orbital
interactions, the bond formation and the evolution of the electronic properties
with oxidation or reduction of the porphyrins in supramolecular donor-acceptor
complexes used in photovoltaic devices.
