Null Exciton Splitting in Chromophoric Greek Cross (+) Aggregate

Abstract

Exciton interactions in molecular aggregates play a crucial role in tailoring the optical behavior 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-Br2) which exhibits null exciton coupling mediated monomer-like optical characteristics in crystalline state. Contrastingly, nonzero exciton coupling in X-type (α = 70.2°, PTE-Br0) and J-type (α = 0°, θ = 48.4°, PTE-Br4) assemblies render perturbed optical properties. Additionally, the semi-classical Marcus theory of charge-transfer rates predicts a selective hole transport phenomenon in the orthogonally stacked PTE-Br2. Precise rotation angle dependent optoelectronic properties in crystalline PTE-Br2 can have consequences in the rational design of novel π-conjugated materials for photonic and molecular electronic applications.