Versatility of the Cyano Group in Intermolecular Interactions

Area of Science:

• Computational Chemistry
• Supramolecular Chemistry
• Organic Chemistry

Background:

• Lewis acids with positive electrostatic potential regions are crucial for molecular recognition.
• Cyano groups (C≡N) are known electron-withdrawing substituents.
• Understanding noncovalent interactions is fundamental in chemistry.

Purpose of the Study:

• To investigate the formation of intense positive electrostatic potential regions by multiple cyano groups.
• To quantify the strength and nature of noncovalent bonds formed between these Lewis acids and ammonia (NH3).
• To explore the influence of molecular structure on binding affinity.

Main Methods:

• Computational modeling was used to design and analyze molecules with multiple cyano substituents on alkane, alkene, and alkyne frameworks.
• Density Functional Theory (DFT) calculations were employed to determine electrostatic potential and binding energies.
• Analysis of noncovalent interactions, including tetrel bonds, was performed.

Main Results:

• Multiple cyano groups synergistically create a strong positive electrostatic potential region (π-hole) midway between them.
• Ammonia (NH3) forms strong noncovalent bonds with these Lewis acids, with binding energies up to 13.6 kcal/mol.
• The binding involves tetrel bonds to carbon atoms of the cyano groups or connecting linkers. Cyclic systems slightly weaken binding, and fluorine substituents are less effective than cyano groups.

Conclusions:

• Strategically placed cyano groups can generate potent Lewis acid sites capable of strong ammonia binding.
• The synergistic effect of multiple cyano groups offers a tunable approach for designing molecules with specific noncovalent interaction properties.
• This study highlights the potential of cyano-functionalized molecules in supramolecular chemistry and materials design.