Covalent Control of Excitonic Interactions in Perylene Diimide Trimers: A Computational Study

Le résumé fourni par la source

Covalently tethering chromophores is an emerging strategy to control the structure and function of supramolecular aggregates for organic electronic applications. In this study, we employ first principle calculations to elucidate structure-property relationships in three perylene diimide (PDI) trimer systems: a non-covalent assembly (u-PDI3), a stapled assembly (t-PDI3), and a folded (foldamer) assembly, (s-PDI3) in aqueous solvent. Our results show how tethering controls inter-chromophore geometry, particularly twist angles and slip displacements, which determine electronic coupling patterns. The t-PDI3 system enforces symmetric cofacial alignment with small twist angles, producing high charge-transfer (CT) character across low-lying excited states, strong coupling (0.16-0.17 eV), and the largest exciton bandwidth. In contrast, u-PDI3 features varying electronic transition character and coupling heterogeneity (0.07-0.15 eV), while s-PDI3 has uniform CT character with moderate coupling strength (0.10-0.14 eV). The findings highlight how covalent tethering can be engineered to tune excitonic and charge-transfer properties in π-stacked molecular aggregates.

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