Supramolecular environment-dependent electronic properties of metal-organic interfaces

Model donor acceptor assemblies at metal organic interfaces, namely, fluorinated copper-phthalocyanines (F16CuPC) and pentacene (PEN) assemblies on the Au(111) surface, have been the focus of the present study. A full picture of the crystallographic and electronic structure of PEN and F16CuPC monolayers as well as of their 1:1 binary mixture on the Au(111) surface has been explored by means of a variety of surface-sensitive techniques, providing important information on the intermolecular and molecule-substrate interactions governing the self-assembly process. A long-range ordered donor acceptor network is observed for the mixture as a result of the greatly enhanced intermolecular interaction via C-F center dot center dot center dot H-C hydrogen bonds. Interestingly, the new supramolecular structure involves changes in the electronic structure of the molecular components. In particular, the strongest changes are observed at the C and F atoms of the F16CuPc, as opposed to the F16CuPc N, Cu, or PEN C atoms. With the aid of theoretical calculations, such effects are found to be at least partially related to an upward shift in energy of the F16CuPc molecular orbitals, concomitant with a molecule-to-metal charge donation, not from the HOMO, but deeper lying orbitals.