# Accurate Calculation of Electron Paramagnetic Resonance Parameters for Molybdenum Compounds

## TL;DR

This paper identifies the best computational methods for accurately predicting EPR parameters of molybdenum compounds, important for understanding their electronic structure.

## Contribution

A curated database of Mo(V) compounds and evaluation of quantum chemical protocols for EPR parameters is presented.

## Key findings

- Unmodified SARC basis sets with X2C Hamiltonian yield converged HFC and g-values for Mo compounds.
- PBE0-DH functional provides best agreement with experimental HFCs and is recommended for EPR calculations.
- DFT remains preferable over DLPNO-CCSD for HFCs in Mo complexes.

## Abstract

Paramagnetic molybdenum compounds are of great interest in inorganic chemistry and metalloenzyme catalysis. Electron paramagnetic resonance (EPR) spectroscopies that determine hyperfine coupling constants (HFCs) and g‐tensor values are essential for investigating the electronic structure of these compounds, but require support from accurate quantum chemical approaches. Here, a database of Mo(V) complexes with well‐defined structures and EPR parameters is presented, and optimal quantum chemical protocols for 95Mo HFCs and g‐values are investigated. It is shown that unmodified segmented all‐ electron relativistically contracted (SARC) all‐electron basis sets can produce converged results for HFCs and g‐values with the exact‐2‐component (X2C) Hamiltonian. The dependence of EPR parameters on the functional is studied in detail. Double‐hybrid functionals and global hybrids with high exact exchange are top performers for 95Mo HFCs, with PBE0‐DH achieving the best agreement with experiment. Comparison of density functional theory (DFT)‐derived HFCs with values obtained by coupled cluster theory with the domain‐based local pair natural orbital approach (DLPNO‐CCSD) shows that DFT remains the method of choice for the present set of compounds. Smaller differentiation among functionals is observed for g‐tensors, although PBE0‐DH is still a top performer and can be recommended as the most reliable approach overall for describing both valence and core properties of Mo compounds.

Using a curated database of experimentally characterized, biologically relevant Mo(V) compounds, this study evaluates the optimal choice of basis sets, density functionals, and wavefunction methods for accurately computing g‐tensor values and 95Mo hyperfine coupling constants, with the goal of establishing reliable protocols for predicting electron paramagnetic resonance of molybdenum complexes and enzyme cofactors.© 2025 WILEY‐VCH GmbH