Inverse Optically-Induced Ring Currents in Ring-Shaped Molecules

Area of Science:

• Quantum Chemistry
• Molecular Physics
• Electronic Structure Theory

Background:

• Permanent electronic ring currents exist in degenerate excited electronic states (Γ_E).
• Previous work identified inverse-current manifolds where electronic current opposes light polarization, attributed to vibronic coupling.
• The role of pure electronic structure in supporting such currents was not fully explored.

Purpose of the Study:

• To investigate the existence of inverse-current manifolds in ring-shaped molecules based solely on electronic structure.
• To elucidate the underlying electronic mechanisms responsible for inverse-current formation.
• To provide a computational framework for identifying these manifolds in molecules.

Main Methods:

• Theoretical modeling using a tight-binding model with cyclic symmetry.
• Ab initio electronic structure calculations for benzene and sym-triazine.
• Analysis of electronic orbital angular momentum and current generation.

Main Results:

• Ring-shaped molecular systems demonstrate inverse-current manifolds on a purely electronic-structure basis, independent of vibronic coupling.
• The tight-binding model and ab initio calculations confirm the electronic origin of inverse currents.
• A method is proposed to distinguish between regular and inverse-current manifolds using quantum chemistry.

Conclusions:

• Inverse electronic ring currents can arise from intrinsic electronic properties of molecules, particularly in ring systems.
• This finding expands the understanding of electronic dynamics in excited states beyond vibronic effects.
• The developed framework facilitates the identification and study of inverse-current phenomena in various molecular systems.