Greek Cross (+) Aggregate: A Paradigm for Exciton Isolation

The exciton theory formulated by Kasha and co-workers and Davydov independently gave the fundamental understanding of the photophysics of molecular aggregates.1 Kasha demonstrated exciton splitting for various geometrical orientations of molecular transition dipoles based on the long-range Coulombic coupling employing the point dipole approximation. The molecular exciton theory highlighted the significance of the orthogonal arrangement of transition dipoles in isolating the exciton and subsequent null exciton coupling mediated monomer-like optical properties.2 The emergent photophysical properties from the crafted architectures were explored using both experimental tools and the state-of the-art computational methods for understanding the aggregates beyond the Kasha’s model. 

(1) Kasha, M.; Rawls, H. R.; El-Bayoumi, M. A. Pure Appl. Chem. 1965, 11, 371–392. 

(2) Sebastian, E.; Hariharan, M. J. Am. Chem. Soc. 2021, 143, 34,13769-13781.