Non-covalent intermolecular carbon-carbon interactions in polyynes

Area of Science:

• Computational Chemistry
• Materials Science
• Organic Chemistry

Background:

• Polyynes, linear carbon allotropes related to carbyne, are investigated for their intermolecular interactions.
• Understanding these interactions is crucial for designing novel molecular materials.

Purpose of the Study:

• To investigate the type and strength of non-covalent interactions in polyyne dimer and tetramer complexes.
• To assess how end-group functionalities and chain length influence interaction energy.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Molecular Electrostatic Potential (MEP) analysis and Quantum Theory of Atoms-in-Molecules (QTAIM) were used for characterization.

Main Results:

• Non-covalent carbon-carbon (CC) interactions were identified, driven by electrostatic complementarity between triple and single bonds.
• Interaction energy (Eint) increased significantly with polyyne chain length, from -1.07 kcal mol⁻¹ for acetylene dimer to -45.83 kcal mol⁻¹ for 50yne dimer.
• End-group substitutions and tetramer formation further enhanced interaction energies, showing strong cooperativity.

Conclusions:

• CC interactions play a key role in stabilizing polyyne dimers and tetramers.
• The significant energy gains in larger polyyne complexes predict the formation of stable polyyne bundles.
• These findings offer insights for the design of new functional molecular materials.