Discrete Dimers of Redox-Active and Fluorescent Perylene Diimide-Based Rigid Isosceles Triangles in the Solid State

Area of Science:

• Organic materials science
• Photonics and optoelectronics
• Supramolecular chemistry

Background:

• Rigid covalent chiroptical organic materials with multiple redox states are crucial for organic electronics and photonics.
• Perylene diimide (PDI) fluorophores offer high fluorescence but suffer from aggregation-caused emission quenching in the solid state.

Purpose of the Study:

• To design and synthesize chiral isosceles triangles incorporating PDI and pyromellitic diimide (PMDI) or naphthalene diimide (NDI) units.
• To investigate the optical, electronic, and magnetic properties of these novel triangular structures.
• To address the challenge of solid-state emission quenching in PDI derivatives.

Main Methods:

• Synthesis of chiral isosceles triangles with PDI, PMDI, or NDI units.
• Characterization using optical spectroscopies, single-crystal X-ray diffraction (XRD), and cyclic voltammetry.
• Computational modeling to understand electronic and optical properties.

Main Results:

• Synthesized rigid triangular molecules with PDI and NDI/PMDI units.
• Observed discrete, nearly cofacial PDI-PDI π-dimers in the solid state via XRD.
• Achieved high fluorescence quantum yields in solution, with significant solid-state excimer fluorescence.
• Demonstrated superior intramolecular energy transfer in NDI-PDI containing triangles.
• Confirmed multiple, accessible, and reversible redox states through cyclic voltammetry.

Conclusions:

• The designed rigid triangular structures effectively mitigate solid-state aggregation-caused quenching.
• These materials exhibit promising photoluminescence and redox properties for molecular optoelectronic devices.
• The study provides a pathway for developing advanced chiroptical organic materials.