Intermolecular orbital interaction in π systems

ABSTRACT

Intermolecular interactions, in regard to which people tend to emphasise the noncovalent van der Waals (vdW) forces when conducting investigations throughout chemistry, can influence the structure, stability and function of molecules and materials. Despite the ubiquitous nature of vdW interactions, a simplified electrostatic model has been popularly adopted to explain common intermolecular interactions, especially those existing in π-involved systems. However, this classical model has come under fire in revealing specific issues such as substituent effects, due to its roughness; and it has been followed in past decades by sundry explanations which sometimes bring in nebulous descriptions. In this account, we try to summarise and present a unified model for describing and analysing the binding mechanism of such systems from the viewpoint of energy decomposition. We also emphasise a commonly ignored factor – orbital interaction, pointing out that the noncovalent intermolecular orbital interactions actually exhibit similar bonding and antibonding phenomena as those in covalent bonds.

KEYWORDS:

• Orbital interactions
• noncovalent van der Waals interactions
• π systems

Acknowledgments

We acknowledge the Beijing Computational Science Research Center, Beijing, China, for allowing us to use its Tianhe2-JK computing cluster.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Environmental Conservation Fund (ECF) of Hong Kong [project number 9211100 (29/2015)]