Hydrogen bonding patterns of calix[4]arenes with thiourea functionalities in solution and in the solid state

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Materials Science

Background:

• Calixarenes are versatile macrocyclic compounds with tunable properties.
• Thiourea moieties are known for their hydrogen bonding capabilities and coordination chemistry.
• Functionalization of calixarene upper rims is crucial for developing advanced molecular architectures.

Purpose of the Study:

• To synthesize novel calix[4]arene derivatives incorporating thiourea functional groups.
• To selectively prepare mono- and di-substituted calix[4]arenes and their dimers.
• To investigate the structural and hydrogen bonding characteristics of these new compounds.

Main Methods:

• Synthesis via condensation of 1,3-di(p-amino)calix[4]arene with alkyl isothiocyanates.
• Selective preparation of mono- and dithiourea-substituted calix[4]arenes.
• Homocoupling reactions to form calix[4]arene dimers.
• Structural characterization using X-ray crystallography and 1H NMR spectroscopy.
• Computational studies to analyze hydrogen bonding patterns.

Main Results:

• Successfully synthesized various calix[4]arene derivatives bearing thiourea groups at the upper rim.
• Achieved selective synthesis of mono- and dithiourea derivatives in good yields.
• Prepared calix[4]arene dimers linked by thiourea groups through homocoupling.
• X-ray crystallography revealed intricate intra- and intermolecular hydrogen bonding networks.
• 1H NMR and computational data corroborated the observed hydrogen bonding patterns.

Conclusions:

• Novel calix[4]arene-thiourea conjugates were efficiently synthesized.
• The study elucidated the formation of unique hydrogen bonding motifs in these derivatives and dimers.
• These findings contribute to the design of new supramolecular structures and functional materials based on calixarenes.