Null Exciton Splitting in Chromophoric Greek Cross (+) Aggregate

Abstract Exciton interactions in molecular aggregates play a crucial role in tailoring the optical behaviour of π‐conjugated materials. Though vital for optoelectronic applications, ideal Greek cross‐dipole ( α =90°) stacking of chromophores remains elusive. We report a novel Greek cross (+) assembly of 1,7‐dibromoperylene‐3,4,9,10‐tetracarboxylic tetrabutylester (PTE‐Br 2 ) which exhibits null exciton coupling mediated monomer‐like optical characteristics in the crystalline state. In contrast, nonzero exciton coupling in X‐type ( α =70.2°, PTE‐Br 0 ) and J‐type ( α =0°, θ =48.4°, PTE‐Br 4 ) assemblies have perturbed optical properties. Additionally, the semi‐classical Marcus theory of charge‐transfer rates predicts a selective hole transport phenomenon in the orthogonally stacked PTE‐Br 2 . Precise rotation angle dependent optoelectronic properties in crystalline PTE‐Br 2 can have consequences in the rational design of novel π‐conjugated materials for photonic and molecular electronic applications.