Preserving chemical reactivity on oxygen-passivated Fe via axial coordination to an ordered ZnTPP monolayer

he preservation of molecular reactivity on catalytic surfaces is one of the main key challenges in the fabrication of ordered organic–inorganic hybrid architectures. In this work, we investigate the behavior of a prototypical reactive molecule: a bromo-substituted naphthalimide derivative (Br-PNI) deposited in ultra-high vacuum on an iron passivated surface, either left as-prepared or pre-covered with an ordered zinc porphyrin monolayer. X-ray photoelectron spectroscopy reveals that the bare iron passivated surface promotes partial cleavage of the carbon–bromine bond even at room temperature, suggesting a catalytic activity toward dehalogenation reactions. This is also consistent with the flat-lying configuration of these molecules, as assessed by near-edge x-ray absorption fine structure (NEXAFS) analysis, which promotes direct contact with the substrate. In contrast, when Br-PNI is deposited on top of the zinc porphyrin monolayer, wetting the entire surface, axial coordination between the zinc ion and the Br-PNI pyridyl group induces an upright, out-of-plane molecular orientation, effectively separating the reactive bromine substituent from the catalytic surface. These results demonstrate that axial coordination with ordered porphyrin monolayers can simultaneously control molecular orientation and inhibit unwanted surface-catalyzed reactions, thereby providing a general strategy for integrating reactive functional groups into well-defined multilayer architectures.