Noncovalent Lone Pair⋅⋅⋅(No-π!)-Heteroarene Interactions: The Janus-Faced Hydroxy Group

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Chemical Physics

Background:

• Noncovalent interactions are crucial in molecular recognition and self-assembly.
• Hydrogen bonding to aromatic systems is a well-studied interaction.
• The role of electron-deficient heteroarenes in noncovalent interactions requires further investigation.

Purpose of the Study:

• To compare the strength and solvent dependence of hydroxy group interactions with heteroarenes versus benzene.
• To investigate the binding preferences of alkyl fluorides with heteroarenes and benzene.
• To quantify the attractive interaction between quinoxaline and terminal alkynes.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to study molecular interactions.
• Designed top-pan molecular balances were utilized for quantitative interaction measurements.
• Comparative analysis of interaction strengths in different solvent environments.

Main Results:

• Hydroxy groups form significantly stronger, solvent-independent lone pair-heteroarene interactions with pyrazine and quinoxaline compared to π-facial hydrogen bonds to benzene.
• Alkyl fluorides demonstrate a preference for interacting with heteroarene rings over benzene.
• The attractive interaction between quinoxaline and a terminal alkyne surpasses the strength of intramolecular hydrogen bonds to arenes.

Conclusions:

• Electron-deficient heteroarenes are potent interaction partners, outperforming benzene in noncovalent interactions with hydroxyl groups and alkyl fluorides.
• Lone pair-heteroarene interactions represent a strong and versatile binding motif in supramolecular chemistry.
• These findings have implications for the design of novel materials and molecular systems based on specific noncovalent interactions.