3d-Valence orbital structure of Zn-phthalocyanine; results from photoemission experiments and cluster calculations

We have determined the binding energies (initial energies) for the Zn 3d-derived density of states in Zn- phthalocyanine (ZnPC) from photoelectron energy distribution curves obtained with photon energies ranging from 30 to 120 eV by exploiting the strong hv-independence of the 3d partial cross section. The center of the 3d derived states is located 15.2 eV below the vacuum level Evac = 0) and is 1.2 eV wide (fwhm). The experimental results are compared with ab initio Hartree-Fock-LCAO calculations on ZnN4 clusters. The fully relaxed ionization potentials (IP) derived from self-consistent wavefunctions of the different d-hole states of ZnN4 are smaller by about 6 eV with respect to the Koopmans IPs. This relaxation shift brings the calculated center of the 3d derived states in close agreement with experiment. The relative positions of the calculated 3d-type levels in ZnN4 are also consistent with a simple ligand field model of the ZnPC complex where reasonable interaction parameters are used. © 1981.