An Additivity Scheme for Aromaticity: The Heteroatom Case.

Area of Science:

• Computational chemistry
• Theoretical organic chemistry
• Quantum chemistry

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are crucial in various scientific fields.
• Assessing aromaticity and ring currents in PAHs is essential for understanding their properties.
• Nucleus-independent chemical shift (NICS)-XY-Scan is a valuable tool for this assessment.

Purpose of the Study:

• To expand the NICS-XY-Scan additivity scheme to include heteroatomic systems (B, N, O, S).
• To enable rapid and resource-efficient prediction of aromaticity in large, complex molecules.
• To investigate the additive nature of magnetic aromaticity criteria and ring current localization.

Main Methods:

• Utilized an established additivity scheme based on NICS-XY-Scans of smaller molecular fragments.
• Applied the scheme to predict the aromatic profiles of larger PAHs containing heteroatoms.
• Analyzed the resulting NICS-XY-Scans to determine aromaticity and ring current behavior.

Main Results:

• Successfully extended the NICS-XY-Scan additivity approach to systems with B, N, O, and S heteroatoms.
• Demonstrated that the magnetic criterion of aromaticity exhibits additive behavior.
• Observed that ring currents in multi-ring systems are predominantly localized within subunits of up to three rings.

Conclusions:

• The NICS-XY-Scan additivity scheme provides an efficient method for evaluating aromaticity in complex heteroatomic systems.
• The additive nature of magnetic aromaticity criteria simplifies the analysis of large molecular structures.
• Ring current localization in subunits offers insights into the electronic structure and properties of PAHs.