Room temperature chiral discrimination in paramagnetic NMR spectroscopy

TL;DR

This paper extends a theory of chiral discrimination in NMR to paramagnetic systems, predicting larger signals at room temperature, supported by calculations on Dy$^{3+}$ complexes showing significant enhancement over diamagnetic molecules.

Contribution

The authors generalize the existing theory to include paramagnetic molecules, revealing new temperature-dependent contributions to the polarization and demonstrating potential for room temperature chiral detection.

Findings

Paramagnetic molecules exhibit polarization more than 1000 times larger than diamagnetic ones.

The theory predicts a new temperature dependence of the polarization, varying as the inverse square of temperature.

Calculations confirm the feasibility of room temperature chiral discrimination in paramagnetic NMR.

Abstract

A recently proposed theory of chiral discrimination in NMR spectroscopy based on the detection of a molecular electric polarization $\mathbf{P}$ rotating in a plane perpendicular to the NMR magnetic field [A. D. Buckingham, J. Chem. Phys. $\mathbf{140}$, 011103 (2014)], is here generalized to paramagnetic systems. Our theory predicts new contributions to $\mathbf{P}$, varying as the square of the inverse temperature. Ab initio calculations for ten Dy$^{3+}$ complexes, at 293K, show that in strongly anisotropic paramagnetic molecules $\mathbf{P}$ can be more than 1000 times larger than in diamagnetic molecules, making paramagnetic NMR chiral discrimination amenable to room temperature detection.