Concerted Interplay of Excimer and Dipole Coupling Governs the Exciton Relaxation Dynamics in Crystalline Anthracenes

Abstract

We report a conjoint theoretical and experimental investigation on the role of concerted long‐ (dipole coupling) and short‐range (orbital overlap mediated excimer) electronic interactions in modulating the emission of six crystalline acetylanthracenes (1‐3). Friedel‐Crafts acylation of anthracene rendered crystalline acetylanthracenes with discrete close‐packing, varied orbital overlap, and resultant distinct emission (blue‐green‐yellow) from cooperative excimer and dipole coupling. Time‐resolved emission spectral (TRES) studies and Kasha’s exciton theory based quantitative estimation of dipole coupling (mean field approximation) substantiates the exciton dynamics in crystalline 1‐3. Extension of Kasha’s exciton model beyond the traditional nearest‐neighbor approach, and consistent agreement among the computed spectral shifts and TRES temporal components corroborate a holistic approach to decipher the exciton relaxation dynamics in molecular assembly of novel photonic materials.