Role of the Central Metal Atom in Substrate-Mediated Molecular Interactions in Phthalocyanine-Based Heteromolecular Monolayers

Abstract

Molecular monolayer films containing two different types of molecules (so-called heteromolecular films) are promising candidates for the controlled functionalization of metal–organic hybrid interfaces. This is particularly true for blends formed by charge donor and acceptor molecules. Here we study heteromolecular monolayer systems containing 3,4,9,10-perylene-tetra-carboxylic-dianhydride (PTCDA) as charge acceptor, and either copper(II) or tin(II) phthalocyanine (CuPc or SnPc) as charge donor, adsorbed on Ag(111). We find that both systems exhibit structural phases with identical lateral ordering (isostructural phases), which is an important prerequisite for studying the role of the central metal atom without competing effects caused by different lateral structures. Using normal incidence X-ray standing waves and photoemission tomography we find distinct differences in the (vertical) geometric and electronic structure for the heteromolecular systems under study: While the vertical structure of CuPc is es...