Synthesis and Characterization of a Brønsted Pair Functionalized Shape-Persistent Macrocycle

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Physical Chemistry

Background:

• Macrocycles are cyclic molecules with diverse applications in host-guest chemistry and materials science.
• Developing macrocycles with specific internal functionalities remains a key challenge in supramolecular chemistry.
• Shape-persistent macrocycles maintain their conformation, enabling predictable interactions.

Purpose of the Study:

• To describe the synthesis and characterization of the first shape-persistent macrocycle with a Brønsted pair-functionalized interior.
• To investigate the structural and property differences between the synthesized macrocycle and its precursor.
• To explore the origin of observed property variations using theoretical methods.

Main Methods:

• Post-cyclization transformation of a precursor ester (compound 2) to yield the target macrocycle (compound 1).
• Characterization of macrocycle 1 and ester 2, focusing on differences in solubility and appearance.
• Theoretical investigations, including conformational analysis, to elucidate structure-property relationships.

Main Results:

• Successful synthesis of a novel shape-persistent macrocycle (1) featuring a Brønsted pair-functionalized interior.
• Significant differences in solubility and appearance were observed between macrocycle 1 and its precursor ester 2.
• Theoretical studies indicated that a strong O-H-N hydrogen bond within macrocycle 1 likely causes conformational changes, explaining the property disparities.

Conclusions:

• The first shape-persistent macrocycle with a Brønsted pair-functionalized interior has been synthesized.
• The observed dramatic differences in macrocycle characteristics are attributed to conformational changes induced by intramolecular hydrogen bonding.
• This work opens new avenues for designing functional macrocyclic compounds with tunable properties.