Dispersion‐Clamped Crystalline Supramolecular Columnar π‐Stacks of Adamantyl‐Substituted Pyrenes

Abstract

ABSTRACT Despite their importance in supramolecular chemistry, zero‐offset columnar π‐stacks of polycyclic aromatic hydrocarbons (PAHs) are rarely observed in crystals because close cofacial packing is penalized by Pauli repulsion. Here we show a crystalline phase (CP) of adamantyl‐substituted pyrene that exhibits one‐dimensional, translationally aligned columnar π‐stacks enabled by dispersion‐assisted adamantyl “clamps”. Single‐crystal x‐ray diffraction reveals an exceptionally short interplanar separation of 3.297(3) Å at 100 K. Energy‐decomposition analysis shows that the adamantyl substituents provide larger dispersion stabilization relative to their Pauli penalty, rationalizing the formation of the zero‐offset π‐columns. The solution‐to‐crystal color shift is exceptionally large (Δ E obs = −0.761 eV), which exceeds exciton coupling contributions and is dominated by intermolecular orbital interactions captured by a frontier crystal orbital (FCO) model. To the best of our knowledge, both the translationally zero‐offset π‐columns and the large crystallization‐induced red shift are unprecedented for ambient‐pressure CPs of neutral, closed‐shell hydrocarbon PAHs.