Ultraviolet Photoelectron Valence Band Studies on Phthalocyanine Compounds

Ultraviolet photoelectron spectra excited by He I and He II radiation from the valence bands of H 2 Pc (H 2 C 32 H 16 N 8 ), FePc, CuPc, and PtPc are measured for binding energies down to 18 eV. No satisfying agreement of the photoelectron spectra with available molecular orbital calculations is found. Although weak contributions of the central metal d‐electrons can be identified, the spectra are surprisingly similar for all Pc's and represent essentially the π‐electron ring system. They appear to be a superposition of the spectra of benzene and an inner porphin skeleton. A spectral change in H 2 Pc around 10 eV as compared to the metal Pc's is interpreted in terms of different σ‐bonds to the central atoms.