Structural sensitivity without chirality: Observation of magnetic Raman optical activity outside resonance

Magnetic Raman optical activity (MROA) is traditionally associated with systems fulfilling resonance conditions, i.e., those absorbing the excitation radiation. Its presence in far-from-resonance (FFR) regimes, where absorption is negligible, has not been previously reported.

In a recent study, Moumita Das and Petr Bouř from IOCB Prague identified MROA signals under FFR conditions in a range of common organic molecules. This observation challenges the established understanding of the phenomenon and suggests that MROA is more general than previously assumed.

The authors developed a theoretical description of the effect and implemented a computational protocol for simulating MROA intensities. The predicted spectral features show reasonable agreement with experimental data and reproduce observed trends.

The results further indicate that MROA spectra are sensitive not only to molecular identity but also to conformational changes. Researchers also detected this structural sensitivity in solution even when molecules lacked intrinsic chirality.

These findings position MROA as a potentially valuable analytical tool for conformational studies of both chiral and achiral molecules in liquids, with implications for spectroscopy and structural chemistry.

The Original article

Structural Sensitivity without Chirality: Observation of Magnetic Raman Optical Activity outside Resonance

Moumita Das, and Petr Bouř

J. Am. Chem. Soc. 2026, 148, 10, 11058–11067

https://doi.org/10.1021/jacs.5c22470

licensed under CC-BY 4.0

Abstract

Magnetic Raman optical activity (MROA) has been considered to be confined to a few systems fulfilling the resonance conditions. In a far-from-resonance (FFR) case when the systems do not absorb the excitation radiation, it has not been reported. However, we find it present in many common organic molecules. The underlying theory was elaborated, and a procedure for quantum chemical simulations of MROA intensities was implemented. The spectral features predicted at the density functional theory (DFT) level reasonably agree with the observations, describe the trends in the experimental data, and allow one to understand the phenomenon more deeply. It appears that not only do molecules have specific MROA patterns but the intensities are also very much dependent on the conformation. The sensitivity to the structure in solutions without the need for intrinsic molecular chirality makes MROA a unique tool for analytical chemistry and potentially usable for conformational studies of both chiral and achiral molecules in solutions and other liquids.