Perylene Diimide-Embedded Double [8]Helicenes.

Area of Science:

• Organic Chemistry
• Materials Science
• Chiral Science

Background:

• Rational design of helical structures is crucial for developing advanced materials.
• Configurationally stable materials with tailored properties are essential for chiral science applications.

Purpose of the Study:

• To develop a straightforward synthetic approach for novel double helicenes.
• To investigate the structural diversity and chiroptical properties of perylene diimide-embedded double [8]helicenes (PD8Hs).

Main Methods:

• Hybridization of [6]helicene subunits with a perylene diimide (PDI) scaffold.
• Single-crystal X-ray diffraction for absolute configuration determination.
• Chiral High-Performance Liquid Chromatography (HPLC) for enantiomer resolution.
• Circular Dichroism (CD) and Circularly Polarized Luminescence (CPL) spectroscopy.

Main Results:

• Synthesis of unprecedented perylene diimide-embedded double [8]helicenes (PD8Hs), the highest reported double carbohelicenes.
• Identification of six stereoisomers (two pairs of enantiomers, two mesomers) with diverse superhelical structures and packing arrangements.
• Achieved outstanding fluorescence quantum yields (~30%) due to the PDI chromophore.
• Resolved enantiomers and demonstrated excellent chiroptical performance (|g_abs| = 0.012, |g_lum| = 0.002 for PD8H-6R).

Conclusions:

• The developed synthetic strategy enables access to structurally diverse double helicenes.
• PD8Hs exhibit unique stereoisomerism and significant chiroptical properties, suitable for advanced chiral applications.
• Subtle configurational differences profoundly impact molecular structure and optical characteristics.