The adsorption and monolayer self-assembly of functional metal–organic blocks on solid surfaces are critical for the physicochemical properties of these low-dimensional materials. Although modern microscopy tools are very sensitive to the lateral arrangement of such blocks, they are still unable to offer directly the complete structural analysis especially for nonplanar molecules containing different atoms. Here, we apply a combinatorial approach for the characterization of such interfaces, which enables unexpected insights. An archetypal metalloporphyrin on a catalytically active surface as a function of its molecular coverage and substituent arrangement is characterized by low-energy electron diffraction, scanning probe microscopy, X-ray photoelectron spectroscopy, normal-incidence X-ray standing waves, and density functional theory. We look into Ru tetraphenyl porphyrin (Ru-TPP) on Ag(111), which is also converted into its planarized derivates via surface-assisted cyclodehydrogenation reactions. Depending on the arrangement of the phenyl substituents, the Ru atoms have distinct electronic structures and the porphyrin macrocycles adapt differently to the surface: saddle shape (pristine Ru-TPP) or bowl shape (planarized Ru-TPP derivates). In all cases, the Ru atom resides close to the surface (2.59/2.45 Å), preferably located at hollow sites and in the interface between the plane of the porphyrin macrocycle and the Ag surface. For the more flexible pristine Ru-TPP, we identify an additional self-assembled structure, allowing the molecular density of the self-assembled monolayer to be tuned within ∼20%. This precise analysis is central to harnessing the potential of metalloporphyrin/metal interfaces in functional systems.

The normal incidence X-ray standing wave (NIXSW) technique has been used to follow the evolution of the adsorption geometry of Ni adatoms on the Fe3O4(001)-(√2 × √2)R45° surface as a function of temperature.

We report the on-surface synthesis of a nonmetal porphyrin, namely, silicon tetraphenylporphyrin (Si-TPP), by the deposition of atomic silicon onto a freebase TPP layer on a Ag(100) surface under ultrahigh vacuum (UHV) conditions. Scanning tunneling microscopy provides insights into the self-assembly of the TPP molecules before and after Si insertion. Silicon coordinates with all four nitrogen atoms of the TPP macrocycle and interacts with a silver atom of the substrate as confirmed by scanning tunneling spectroscopy, X-ray photoelectron spectroscopy, and complementary density functional theory calculations. The Si-TPP complex presents a saddle-shaped conformation that is stable under STM manipulation. Our study shows how protocols established for the on-surface metalation of tetrapyrroles can be adopted to achieve nonmetal porphyrins. Complementary experiments yielding Si-TPP and Ge-TPP on Ag(111) highlight the applicability to different main group elements and supports. The success of our nonmetal porphyrin synthesis procedure is further corroborated by a temperatureprogrammed desorption experiment, revealing the desorption of Ge-TPP. This extension of interfacial complex formation beyond metal elements opens promising prospects for new tetrapyrrole architectures with distinct properties and functionalities.