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Rotational circular dichroism of diamagnetic and paramagnetic molecules. A computational study
Jiří Zdráhala1,2, Petr Bouř1,2
1Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo náměstí 2, 16610 Prague, Czech Republic.
The Journal of Chemical Physics
|July 11, 2023
Summary
Rotational circular dichroism (RCD) is a novel technique for analyzing chiral molecules. Paramagnetic RCD signals, particularly for radicals, are predicted to be strong enough for experimental measurement.
Area of Science:
- Quantum chemistry
- Molecular spectroscopy
- Chiroptical methods
Background:
- Rotational circular dichroism (RCD) is a predicted spectroscopic technique for chiral molecule analysis.
- Previous predictions indicated weak RCD signals for diamagnetic molecules.
Purpose of the Study:
- To review the quantum-mechanical foundations of RCD.
- To simulate RCD spectral profiles for various molecular systems.
- To assess the feasibility of experimental RCD measurements.
Main Methods:
- Quantum-mechanical calculations of RCD.
- Simulation of spectral profiles for diamagnetic molecules, radicals, and dipeptides.
- Consideration of electric quadrupolar contributions and spectral convolution.
Main Results:
- Electric quadrupolar moment does not contribute to field-free RCD.
- Distinct RCD spectra were simulated for different dipeptide conformers.
- Paramagnetic RCD signals for radicals can reach dissymmetry factors (gK) of ~10-2, suggesting potential measurability.
Conclusions:
- RCD offers a promising route to molecular chirality information.
- Paramagnetic RCD is likely measurable, with typical RCD/absorption ratios around 10-4.
- RCD spectral analysis can distinguish between molecular conformers.
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