Orbital contributions to magnetically induced current densities using gauge-including atomic orbitals

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Molecular Spectroscopy

Background:

• Magnetically Induced Current Density (MICD) is crucial for understanding molecular electronic structure and magnetic properties.
• Quantifying orbital contributions to MICD, particularly magnetically induced ring currents (MIRCs), is essential for accurate theoretical predictions.

Purpose of the Study:

• To develop and apply a method for calculating orbital contributions to MICD susceptibilities.
• To analyze the nature of orbital contributions to MIRC strengths in various molecular systems.

Main Methods:

• Utilized gauge-including atomic orbitals (GIAO) for calculating MICD susceptibilities.
• Employed the GIMIC program to analyze orbital contributions to MIRC strengths.
• Investigated five aromatic, one nonaromatic, and four antiaromatic molecules.

Main Results:

• Orbital contributions to MIRC strength for a given irreducible representation are divergence-free.
• Individual orbital MICD susceptibilities are generally not divergence-free.
• Antiaromatic molecules show dominant HOMO-LUMO transitions for MIRC, while aromatic molecules involve multiple occupied orbitals.
• Significant MIRC contributions from σ orbitals are observed in planar, strained molecules.

Conclusions:

• The developed method provides a robust framework for dissecting orbital contributions to magnetic responses.
• Understanding orbital contributions is key to differentiating aromaticity and antiaromaticity through magnetic criteria.
• The study highlights the importance of specific orbital transitions and types in determining MIRC strengths.