Complexation of fullerenes with 5,5'-Biscalix

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Calixarenes are versatile macrocyclic compounds with tunable host-guest properties.
• Fullerenes (C(60) and C(70)) are important carbon allotropes with unique electronic and structural characteristics.
• Designing selective receptors for fullerenes remains a key challenge in supramolecular chemistry.

Purpose of the Study:

• To synthesize and characterize a novel biscalixarene derivative.
• To investigate the complexation behavior of the synthesized biscalixarene with C(60) and C(70) fullerenes.
• To elucidate the structural basis of the host-guest interaction through X-ray crystallography.

Main Methods:

• Oxidative coupling reaction for the synthesis of 5,5 '-Biscalix[5]arene.
• Spectroscopic techniques (NMR, Mass Spectrometry) for characterization.
• X-ray crystallographic analysis of the free ligand and the C(60) complex.
• UV-Vis titration for determination of association constants.

Main Results:

• 5,5 '-Biscalix[5]arene was successfully synthesized and characterized, revealing an o,u,u,d,u conformation in its tetrabenzoyl ester precursor.
• The biscalixarene forms stable complexes with both C(60) (K(assoc) = 43 M(-)(1)) and C(70) (K(assoc) = 233 M(-)(1)).
• X-ray crystallography of the C(60) complex shows a distinct clamshell-shaped architecture, attributed to a conformational switch from anti to syn upon complexation.

Conclusions:

• The synthesized 5,5 '-Biscalix[5]arene acts as an effective host for C(60) and C(70) fullerenes.
• The observed conformational change is crucial for the efficient binding of the fullerene guests.
• This study provides valuable insights into the design of macrocyclic hosts for fullerene recognition.