Imide Substitution Drives the Supramolecular Assembly of Perylene Diimide Into Laterally Modulated Metallic/Semiconducting Molecular Patterns

Abstract

Perylene dyes are key building blocks in organic optoelectronics and photocatalysis owing to their highly tunable electronic structure. Here, we investigate the impact of imide substitution with bulky 2,6‐isopropylphenyl (iPr) on the structural and electronic properties of perylene diimide (PDI) monolayers on Ag(111). By combining scanning tunneling microscopy, X‐ray absorption and photoemission spectroscopies, we identify two distinct molecular configurations coexisting within an ordered herringbone arrangement. Core level photoemission spectra of monolayer iPr‐PDI reveal two chemically inequivalent oxygen species, which originate from the sterically driven differences in adsorption height. This structural inequivalence translates into markedly different electronic coupling: molecules lying closer to the surface exhibit partial filling of the lowest unoccupied molecular orbitals due to charge transfer from the substrate, whereas those located further away remain electronically decoupled, as evidenced by spectroscopic data and supported by density functional theory calculations. These findings demonstrate that imide substitution can conveniently be exploited for modulating the interfacial electronic character of PDI molecules within a single‐component self‐assembly, since steric effects can modify molecular packing, adsorption height, and molecule–substrate coupling. Our results highlight that substrate‐mediated charge transfer remains a critical design parameter for optimizing charge dynamics in application‐specific organic sensitized heterostructures.