Effects of Structure and Bonding on ¹⁹⁵ Pt Magnetic Shielding Tensors: Insights from Relativistic DFT and Localized Molecular Orbital Analysis

This study examines the use of density functional theory (DFT) calculations with a relativistic Hamiltonian for the prediction of ¹⁹⁵Pt NMR shielding tensors in coordination compounds, as well as the development and application of a method for obtaining quantitative relationships between ¹⁹⁵Pt chemical shift tensors and Pt-ligand bonding. We examine the importance of relativistic effects on ¹⁹⁵Pt magnetic shielding tensors, along with a representative GGA (PBE) and corresponding hybrid (PBE0) DFT functional approximation to determine what is necessary to achieve the best agreement with experiment without reliance upon fortuitous error cancellation. Two methodologies that address the issues of long-range effects on ¹⁹⁵Pt magnetic shielding tensors in solids are compared and contrasted: (i) calculations that treat the extended lattice of Pt-coordination compounds under periodic boundary conditions and (ii) all-electron calculations employing finite clusters as structural models. Natural bond orbital and natural localized molecular orbital analyses examining the contributions of individual orbitals to the ¹⁹⁵Pt magnetic shielding tensors are used to understand their relationship to the electronic structure and Pt-ligand bonding. Finally, the potential of these theoretical methods for investigating a wide range of materials containing platinum group elements is discussed.