Covalent Control of Excitonic Interactions in Perylenediimide Trimers: A Computational Study

Area of Science:

• Materials Science
• Organic Electronics
• Computational Chemistry

Background:

• Controlling supramolecular aggregate structure is key for advanced organic electronic applications.
• Covalently tethering chromophores offers a novel strategy to dictate molecular assembly and function.
• Perylenediimide (PDI) systems are widely studied for their optoelectronic properties.

Purpose of the Study:

• To elucidate structure-property relationships in covalently tethered perylenediimide (PDI) trimers.
• To investigate how different tethering strategies influence electronic coupling and excitonic behavior.
• To provide insights for designing PDI-based materials for organic electronics.

Main Methods:

• First-principles calculations were employed to model three PDI trimer systems: noncovalent (u-PDI3), stapled (t-PDI3), and folded (s-PDI3).
• Analysis focused on interchromophore geometry, including twist angles and slip displacements.
• Electronic coupling, charge-transfer (CT) character, and exciton bandwidth were calculated.

Main Results:

• Covalent tethering significantly controls interchromophore geometry, impacting electronic coupling.
• The stapled t-PDI3 system exhibits symmetric cofacial alignment, leading to strong electronic coupling (0.16-0.17 eV) and high CT character.
• Noncovalent u-PDI3 shows heterogeneous coupling (0.07-0.15 eV), while folded s-PDI3 has uniform CT character with moderate coupling (0.10-0.14 eV).

Conclusions:

• Engineered covalent tethering provides precise control over excitonic and charge-transfer properties in PDI aggregates.
• The findings demonstrate a pathway to tune molecular aggregate properties for specific organic electronic applications.
• This study highlights the potential of foldamer and stapled architectures for advanced materials design.