Copper hexadecafluoro phthalocyanine and naphthalocyanine: The role of shake up excitations in the interpretation and electronic distinction of high-resolution X-ray photoelectron spectroscopy measurements

We present the first high-resolution X-ray photoelectron core level spectra of bulk copper hexadecafluoro phthalocyanine (CuFPC) and naphthalocyanine (H₂NPC). The measurements have been performed in UHV onto samples grown in situ. A shake-up satellite assigned to a monopole on-site HOMO–LUMO molecular excitation has been evidenced in the F, C and N core-level spectra measured. In the case of the CuFPC, the shake-up is characteristic of the F atoms, of the four N atoms that are Cu bonded, and of the F- and N-bonded C atoms. The shake-up to main peak relative binding energy has been estimated to be 1.6 eV. In the case of H₂NPC, the outer benzenic C atoms do not show a satellite excitation, which instead is characteristic of the C and N atoms belonging to the inner porphyrin-like central ring of the molecule. The shake-up is less than 1 eV at higher binding energies from the main core line. The localisation of the HOMO level in the central structure of the molecule is confirmed by Hartree–Fock all-electron molecular orbital calculations performed on the metal-free phthalocyanine (H₂PC) and hexadecafluoro phthalocyanine (H₂FPC) molecules.