Discrete Macrocycles with Fixed Chirality and Two Distinct Sides: Dipole-Dependent Chiroptical Response

Area of Science:

• Molecular Chemistry
• Supramolecular Chemistry
• Chiroptics

Background:

• Molecular symmetry is crucial for designing molecules with specific properties.
• Pillar[5]arene macrocycles offer a versatile platform for creating symmetrical structures.
• Controlling dipolar characteristics is key to tuning chiroptical responses.

Purpose of the Study:

• To synthesize and characterize C5-symmetric pillar[5]arene derivatives with tunable dipolar structures.
• To investigate the impact of dipolar character on chiroptical properties, specifically luminescence.
• To enhance the dissymmetry factor for luminescence in these molecular systems.

Main Methods:

• Synthesis of rim-differentiated pillar[5]arenes.
• Incorporation of electron-withdrawing ester groups to introduce dipolar character.
• Chiroptical measurements of separated enantiomers.
• Spectroscopic analysis to determine luminescence efficiency and response wavelength.

Main Results:

• C5-symmetric pillar[5]arenes with variable dipolar structures were successfully synthesized.
• Electron-withdrawing groups increased response wavelength and luminescence efficiency.
• A strong correlation was observed between dipolar character and electronic transition dissymmetry.
• Suppressing the dipole in a methoxy-substituted derivative enhanced the luminescence dissymmetry factor by an order of magnitude.

Conclusions:

• Molecular dipole suppression is an effective strategy to enhance luminescence dissymmetry in C5-symmetric pillar[5]arenes.
• These findings provide insights into the rational design of advanced chiroptical materials.
• The enhanced dissymmetry factors achieved surpass those of previously reported non-C5-symmetric analogues.