Calculation of NMR Shielding in Paramagnetic Molecules: Roadmap and Magnetic Couplings

TL;DR

This paper derives a simplified method for calculating NMR shielding in paramagnetic molecules, applicable to complex cases involving strong spin-orbit coupling and excited states, with practical computational implementation.

Contribution

It introduces a general theoretical framework for NMR shielding in paramagnetic systems, including a practical expression for zero-field-split ground states, and demonstrates computational application on transition metal complexes.

Findings

Effective calculation of NMR shielding in paramagnetic molecules.

Implementation of the method on Ni(II) and Co(II) complexes.

Extension to strong spin-orbit coupling and excited multiplet contributions.

Abstract

We present a simple derivation of the nuclear shielding in paramagnetic molecules, extendable to strong spin-orbit coupling cases of relevance to lanthanides and actinides, as well as encompassing contributions from excited multiplets. While our general formulation does not need electron paramagnetic resonance parameters, using them a simple and practical expression is obtained for the special case of the zero-field-split ground-state manifold, including magnetic (Zeeman and hyperfine) couplings between the sublevels. The latter method is implemented computationally and applied in the context of first-principles calculations on example Ni(II) and Co(II) complexes.