Structure and Stability of Metalloporphyrin Networks on Au(111)

Abstract

We use density functional theory (DFT) calculations to analyze the properties of FeTPyP self-assembled monolayers (SAMs) and FeTPyP+Fec metal–organic coordination networks (MOCNs) on Au(111). Through a rigorous step-by-step approach, we determine the relative importance of the multiple competing interactions that determine the optimum structure and stability of both networks. For FeTPyP/Au(111) SAMs, we see a complex energy landscape, with molecules preferring to stay at molecule–molecule distances dop ∼ 13.7 and 14.3 Å. Molecule–surface interactions are more prominent in less dense packing (dop ∼ 14.3 Å), and intermolecular interactions favor the compact structure (dop ∼ 13.7 Å). In the case of the FeTPyP–Fec/Au(111) MOCN, the strong Fec–Npy bond between the peripheral iron atom Fec and nitrogen atoms of neighboring pyridyl groups (Npy) is what causes the network development and that the preferred molecule–molecule distance remains at dop ∼ 13.7 Å. Our findings demonstrate the necessity of theoretical treatments that take into account all relevant interactions in order to adequately describe the primary characteristics of surface-supported SAMs and MOCNs.