The electronic structure of iron phthalocyanine (FePc) and interface properties on Ag(111) and Au(100) are investigated by photoexcited electron spectroscopies: photoemission (XPS and UPS) and X-ray absorption spectroscopy (XAS or NEXAFS). Valence band structures with Fe character were identified using resonant photoemission. The strength and nature of the interaction at the interface depend clearly on the substrate. A strong interaction of the central metal atom of the phthalocyanine occurs on Ag(111), whereas no significant changes of the electronic situation were found for FePc on Au(100). Resonant photoemission data show that for FePc on Ag(111) the formed interface states close to the Fermi level are determined by the interaction between Fe 3d states and substrate related states. On the other hand, also the nitrogen atom of FePc is involved in the interaction.

The work was supported by the German Research Council Ch 132/20-2. We acknowledge the Helmholtz-Zentrum Berlin -Electron storage ring BESSY II for provision of synchrotron radiation at the Optics-beamline. Financial travel support by BESSY is gratefully acknowledged. We thank W. Neu for technical support.

Cobalt phthalocyanine (CoPc) monolayer films evaporated on Au(100) are studied by photoexcited electron spectroscopies: X-ray absorption (XAS) and resonant photoemission spectroscopy (ResPES). According to XAS data, the Co 2p absorption spectra look different for monolayer and thicker organic films, pointing to a possible interaction of the molecules with the substrate via the Co d electrons. The contribution of Co-related states in the valence band of CoPc was observed with ResPES. The conclusions are discussed in combination with core-level X-ray photoemission spectroscopy (XPS), X-ray excited Auger electron spectroscopy (XAES), and valence band ultraviolet photoemission spectroscopy (UPS) results previously obtained.

The molecular arrangement and phase transitions in the vanadyl hexadecafluorophthalocyanine (VOPcF 16 ) thin films grown by physical vapor deposition have been studied using in situ X-ray diffraction, atomic force microscopy, and optical spectroscopy techniques (UV, IR, and Raman). The complete transition from the low-temperature linear cofacial structure to the slipped dimeric one occurs in the temperature range 160−220 °C. This conversion was found to be irreversible upon cooling the VOPcF 16 film back to 20 °C. The structural transformation leads to decrease of the in-plane conductivity of the film by 2 orders of magnitude. According to the polarized Raman spectroscopy measurements, the mean tilt angles between the VOPcF 16 species and the substrate surface were 59 ± 5°and 30 ± 5°in the as-deposited and annealed films, respectively. For the sake of comparison, the structure of the thin films of vanadyl phthalocyanine (VOPc) was also studied. The mean tilt angle between the VOPc species and the substrate surface was found to be 77 ± 5°, in good agreement with existing experimental data (∼70°). All intense bands in the experimental IR and Raman spectra of VOPcF 16 and VOPc were assigned using DFT calculations (B3LYP) and the 15 N isotopic shifts in the vibrational spectra of VOPc.

The structures of the DNA and RNA bases cytosine, uracil, and thymine in thin films with a nominal film thickness of about 20 nm are studied by using X-ray photoemission spectroscopy (XPS) and Fourier-transform infrared spectroscopy. The molecules are evaporated in situ from powder on a gold foil. The experimental results indicate that cytosine is composed of two energetically close tautomeric forms, whereas uracil and thymine exist in only one tautomeric form. Additionally, quantum chemical calculations are performed to complement the experimental results. The relative energies of the tautomeric forms of cytosine, uracil, and thymine are calculated using Hartree-Fock (HF), density functional theory (DFT), and post-HF methods. Furthermore, the assignment of the XPS spectra is supported by using simple model considerations employing Koopmans ionization energies and Mulliken net atomic charges.