Photoelectron spectroscopy of phthalocyanine vapors

The 21.2 eV photoelectron spectra of metal-free phthalocyanine and some metal-containing phthalocyanines MPc (M=Mg,Fe,Co,Ni,Cu, and Zn) have been obtained for the gaseous molecules. Comparison of these spectra reveals that the uppermost occupied orbitals are ringlike, and not metal-3d-like, in all cases. Identification of some features in the 1487.6 eV photoemission spectra of thin films of phthalocyanines with similar features in the gas phase spectra enable one to establish an absolute energy scale for the thin film work, and to locate the ionization energies of the 3d-like orbitals. The experimental results and inferences are compared with recent ab initio calculations, and indicate that the Xα local density method is a promising one for describing the electronic structure of these large molecules and the generically related biological systems, chlorophyll and hemoglobin. In some spectra, phthalonitrile was identified as an impurity, and verified by obtaining the 21.2 and 40.8 eV photoelectron spectra of this molecule