Core-electron contributions to the molecular magnetic response.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Magnetic Resonance

Background:

• Orbital contributions significantly influence molecular magnetic responses.
• Current methods using natural localized molecular orbitals (NLMOs) can yield anomalous core contributions.
• This ambiguity impacts the interpretation of magnetic properties and aromaticity in complex molecules.

Purpose of the Study:

• To develop a reliable method for dissecting orbital contributions to magnetic shielding.
• To accurately determine core contributions to magnetic response.
• To resolve discrepancies in magnetic response interpretations for nonplanar molecules.

Main Methods:

• Implementing a Remove Valence Electrons (RVE) approach.
• Calculating core- and σ-components of induced magnetic fields and current densities.
• Performing calculations on highly charged molecules (e.g., C6H6^30+) using GIAO and CMO bases.

Main Results:

• The RVE approach demonstrates that core contributions to magnetic response are minimal and localized at the nuclei.
• This contrasts sharply with findings from Natural Chemical Shielding (NCS) analyses.
• Anomalous core contributions previously reported are attributed to methodological artifacts.

Conclusions:

• The RVE method provides an accurate and cost-effective way to assess core and σ-electron contributions to magnetic response.
• Accurate core contribution assessment is crucial for correct magnetic shielding interpretation, especially for nonplanar systems.
• This work refines our understanding of magnetic properties in molecules like C60 and [14]helicene.