Relativistic Frozen Density Embedding calculations of solvent effects on the NMR shielding constants of transition metal nuclei

TL;DR

This paper assesses relativistic density functional theory methods for calculating solvent effects on NMR shielding constants of transition metals, comparing frozen density embedding with a relax-and-thaw approach.

Contribution

It introduces and evaluates a relativistic FDE method with a freeze-and-thaw procedure for solvent effect calculations on transition metal NMR shielding constants.

Findings

Relax-and-thaw approach improves solvent effect description.

FDE deficiencies are significant in some cases.

Relativistic DFT can effectively model transition metal NMR shifts.

Abstract

Nuclear Magnetic Resonance (NMR) shielding constants of transition metals in solvated complexes are computed at the relativistic density functional theory (DFT) level. The solvent effects evaluated with subsystem-DFT approaches are compared with the reference solvent shifts predicted from supermolecular calculations. Two subsystem-DFT approaches are analyzed -- in the standard frozen density embedding (FDE) scheme the transition metal complexes are embedded in an environment of solvent molecules whose density is kept frozen, in the second approach the densities of the complex and of its environment are relaxed in the "freeze-and-thaw" procedure. The latter approach improves the description of the solvent effects in most cases, nevertheless the FDE deficiencies are rather large in some cases.