Two-ring chirality generated by the alignment of two achiral phenylacetylene macrocycles

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Physical Chemistry

Background:

• Achiral components can generate chirality upon mechanical binding.
• The chiroptical properties of such assemblies depend on the relative orientation of the constituent rings.
• Previous studies showed distinct chiroptical properties in isomeric assemblies of phenylacetylene macrocycles (PAMs).

Purpose of the Study:

• To synthesize a novel two-ring chiral analog by fusing phenylacetylene macrocycles (PAMs).
• To investigate the chiroptical properties of the synthesized analog.
• To elucidate the relationship between ring alignment and chiroptical characteristics.

Main Methods:

• Synthesis of a two-ring chiral analog (4) via ring-fusion of two 6-phenylacetylene macrocycles (6PAMs) to an 11-phenylacetylene macrocycle (11PAM).
• Characterization of chiroptical properties, including molar circular dichroism and molar optical rotation.
• Comparative analysis of chiroptical data between isomeric assemblies (1 and 2) and the synthesized analog (4).

Main Results:

• The synthesized two-ring chiral analog (4) exhibited distinct chiroptical properties.
• Comparison with isomeric assemblies (1 and 2) revealed significant differences in molar circular dichroism and molar optical rotation.
• The observed disparities in chiroptical properties were directly correlated with the specific alignment of the achiral phenylacetylene macrocycle rings.

Conclusions:

• The study successfully synthesized a novel chiral molecule from achiral precursors.
• The alignment of phenylacetylene macrocycle rings is a critical factor in determining the chiroptical response of the assembly.
• This work provides a foundation for designing molecules with tunable chiroptical properties based on mechanical bond architecture.