Weakly Self-Assembled [6]Helicenes: Circularly Polarized Light and Spin Filtering Properties

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Chiroptical activity and spin filtering are crucial properties for advanced electronic and optical applications.
• [6]Helicenes are promising chiral scaffolds, but their self-assembly and spin properties require further investigation.
• Peripheral functionalization can tune the properties of molecular systems.

Purpose of the Study:

• To synthesize and characterize novel 2,15- and 4,13-disubstituted [6]helicene derivatives.
• To investigate the self-assembling behavior and its influence on chiroptical properties.
• To explore the spin filtering capabilities and chiral induced spin selectivity (CISS effect) of these systems.

Main Methods:

• Synthesis of [6]helicenes functionalized with 3,4,5-tris(dodecyloxy)-N-(4-ethynylphenyl)benzamide moieties.
• Characterization of chiroptical properties in monomeric and aggregated states.
• Measurement of spin polarization using magnetic-conducting atomic force microscopy (AFM).

Main Results:

• The synthesized [6]helicene derivatives exhibit weak self-assembly, influenced by peripheral amide groups and steric effects.
• Chiroptical properties remain similar in both monomeric and aggregated states, despite H-bonding interactions.
• Significant chiral induced spin selectivity (CISS effect) was observed, with experimental spin polarization (SP) values ranging from 35-40%.

Conclusions:

• Peripheral functionalization of [6]helicenes can lead to materials with tunable self-assembly and spin properties.
• The weak self-assembly does not significantly alter chiroptical characteristics but conditions the CISS effect.
• These findings highlight the potential of functionalized [6]helicenes for applications in chiral electronics and spintronics.