Quantifying Vertical Resonance Energy in Aromatic Systems with Natural Bond Orbitals

10 October 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Natural bond orbitals (NBOs) provide the familiar Lewis type (2c-2e-) localized description of a molecule. Interactions between nearly filled (2e-) orbitals and empty (π* or σ*) anti-bonding orbitals represent delocalization in the system and creates a framework to study stereoelectronic interactions. Here we show that deleting the interactions between π and π* orbitals in aromatic systems and acquiring the energy with the NBO program provides a highly intuitive and quantitative picture of π-aromaticity that correlates with the well-established nucleus-independent chemical shift (NICS) method. This natural bond orbital resonance energy (NBO-RE) measures the vertical resonance energy (VRE) of aromatic systems without the use of an external reference structure. The NBO-RE method is applicable to the study of local aromaticity in polycyclic aromatic hydrocarbons (PAHs) and other non-planar systems.


Natural Bond Orbitals
Resonance Energy

Supplementary materials

Supplementary Material for Quantifying Vertical Resonance Energy in Aromatic Systems with Natural Bond Orbitals
Computational methods, NBO-RE calculation procedure and data.


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.