Probing ring currents in Mg-porphyrins by pump-probe spectroscopy

Area of Science:

• Quantum chemistry
• Molecular spectroscopy
• Photochemistry

Background:

• Theoretical studies predict strong ring currents in Mg-porphyrin molecules upon excitation with circularly polarized light.
• These induced ring currents can exceed those generated by external magnetic fields.

Purpose of the Study:

• To investigate the potential of circular dichroism (CD) spectroscopy for detecting and quantifying induced ring currents in Mg-porphyrin molecules.
• To establish a link between the CD signal magnitude and the probability of ring current formation.

Main Methods:

• Computational modeling of Mg-porphyrin molecules.
• Simulation of excitation with circularly polarized laser pulses.
• Analysis of the resulting circular dichroism spectra.

Main Results:

• The circular dichroism signal is shown to be directly proportional to the probability of the induced ring current.
• This spectroscopic method provides a sensitive probe for detecting these currents.
• The technique is analogous to magnetic circular dichroism (MCD) in probing excited state symmetries.

Conclusions:

• Circular dichroism spectroscopy is a viable method for detecting and characterizing light-induced ring currents in Mg-porphyrin.
• This approach offers a novel way to study molecular magnetism and excited-state properties.
• The findings pave the way for exploring new spectroscopic techniques in molecular science.