Central sp ³ ‐C Substitution Directs Supramolecular Assembly and Molecular Properties of Tris‐HBC Nanographenes

ABSTRACT

Understanding how structural modifications control the electronic and supramolecular behavior of hexa‐ peri ‐hexabenzocoronene (HBC) nanographenes remains a central challenge in π ‐conjugated materials design. Here, we demonstrate that variation of a central sp ³ ‐C substituent in tris‐HBC( t Bu) ₅ nanographenes modulates the electronic structure through combined through‐bond and through‐space effects. Single‐crystal X‐ray diffraction reveals a pronounced substituent‐size dependence on supramolecular organization. The ─CH ₃ derivative assembles exclusively via π–π stacking into well‐separated two‐dimensional parallel layers with one‐dimensional channels. In contrast, the ─H analogue adopts offset antiparallel layered assemblies driven by cooperative π–π and C─H⋯arene edge contacts, bringing adjacent layers into closer proximity. Notably, solvent‐mediated hydrogen‐bonding induces a distinct layered arrangement in the ─OH analogue. The bulkier ─OCH ₃ and ─OC ₂ H ₅ substituents disrupt this packing motif, with only two HBC units participating in intermolecular π–π stacking, while the third engages in C─H⋯ π interactions with a differently oriented neighboring unit, leading to a different packing arrangement. Consistent with these structural differences, systematic variations in redox potentials, photophysical responses, excited‐state lifetimes, and vibrational features are observed, in good agreement with density functional theory (DFT) and time‐dependent DFT calculations. Overall, central sp ³ substitution provides an effective strategy for tuning structure–property relationships in tris‐HBC nanographenes.