Tricalixarenes and pentacalixarenes: synthesis and complexation studies

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Host-Guest Chemistry

Background:

• Calixarenes are well-established macrocyclic hosts with tunable properties.
• Developing novel macrocyclic architectures is crucial for advancing host-guest chemistry.
• Tricalixarenes represent a unique class of macrocycles with potential for complexation.

Purpose of the Study:

• To synthesize novel tricalixarene and pentacalixarene compounds.
• To investigate the complexation behavior of these new macrocycles with small molecules and C60 fullerene.

Main Methods:

• Synthesis of tricalix[4]arene, tricalix[5]arene, and pentacalix[4]arene via a two-step process involving ethynyl ketone intermediates.
• Aryne trimerization reaction in refluxing N,N-dimethylformamide (DMF) with a dialkylamine.
• Conversion of tricalixarenes to derivatives with lower rim hydroxyl groups and methylene bridges.
• Complexation studies using techniques to determine stoichiometry and binding interactions.

Main Results:

• Successful synthesis of tricalix[4]arene 4, tricalix[5]arene 14, and pentacalix[4]arene 10.
• Tricalix[5]arene 16 formed a 1:3 complex with N,N-dimethylethylenediamine.
• Tricalix[5]arene 16 formed a 1:1 complex with tris(aminomethyl)amine.
• Tricalix[5]arene 16 formed a 1:1 complex with C60 fullerene, with the guest likely residing within the macrocyclic cavity.

Conclusions:

• The synthesized tricalixarenes and pentacalixarenes are novel macrocyclic hosts.
• Tricalix[5]arene 16 exhibits versatile complexation capabilities with diamines and C60.
• The cooperative effect of multiple calixarene units in tricalixarene 16 facilitates guest binding, particularly for C60.