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Description
The interaction of conjugated organic molecules with oxide surfaces is of fundamental interest and relevant for applications ranging from optoelectronics to model catalysis. While organic/metal interfaces are well studied, the behavior on the transparent conductive oxide In₂O₃ remains comparatively unexplored. We investigate the adsorption of metal phthalocyanines (MPc) and metal free phthalocyanine (H₂Pc) on In₂O₃(111) using low temperature scanning tunneling microscopy (STM), non contact atomic force microscopy (nc AFM), and density functional theory (DFT). The comparable size of the molecules and the surface unit cell enables a (1×1) arrangement despite symmetry mismatch (4 fold rotational symmetry of the molecule vs. 3 fold surface symmetry). Across different MPc species (CuPc, CoPc, etc.), we identify a common, robust adsorption site that enforces molecular overlap in the first layer, and a less frequent site that allows non overlapping (1×1) packing. Including H₂Pc reveals how the macrocycle interacts with the oxide in the absence of a metal center, providing a reference for understanding metal dependent adsorption. These insights link phthalocyanines to concepts in single atom catalysis: the Pc macrocycle stabilizes isolated metal atoms in a well defined N₄ pocket. Our results highlight how oxide surfaces—and by extension carbon–nitride like motifs—may offer more robust platforms for stabilizing single metal atoms, bridging molecular model systems and extended SAC materials.