Benchmark Study on the Calculation of ¹¹⁹Sn NMR Chemical Shifts

Abstract

A new benchmark set termed SnS51 for assessing quantum chemical methods for the computation of 119Sn NMR chemical shifts is presented. It covers 51 unique 119Sn NMR chemical shifts for a selection of 50 tin compounds with diverse bonding motifs and ligands. The experimental reference data are in the spectral range of ±2500 ppm measured in seven different solvents. Fifteen common density functional approximations, two scalar- and one spin–orbit relativistic approach are assessed based on conformer ensembles generated using the CREST/CENSO scheme and state-of-the-art semiempirical (GFN2-xTB), force field (GFN-FF), and composite DFT methods (r2SCAN-3c). Based on the results of this study, the spin–orbit relativistic method combinations of SO-ZORA with PBE0 or revPBE functionals are generally recommended. Both yield mean absolute deviations from experimental data below 100 ppm and excellent linear regression determination coefficients of ≤0.99. If spin–orbit calculations are not affordable, the use of SR-ZORA with B3LYP or X2C with ωB97X or M06 may be considered to obtain qualitative predictions if no severe spin–orbit effects, for example, due to heavy nuclei containing ligands, are expected. An empirical linear scaling correction is demonstrated to be applicable for further improvement, and respective empirical parameters are given. Conformational effects on chemical shifts are studied in detail but are mostly found to be small. However, in specific cases when the ligand sphere differs substantially between conformers, chemical shifts can change by up to several hundred ppm.

London Dispersion Effects in a Distannene/Tristannane Equilibrium: Energies of their Interconversion and the Suppression of the Monomeric Stannylene Intermediate

“…Upon heating the solution, the signal for 3 diminishes in intensity and a new signal appeared at δ=417.5 ppm (computational study revealed a δ calc . of 505.9 ppm for the dimer 2 ) [35, 36] . This new signal intensifies as the temperature is increased further.…”

“…= À 340.1 ppm for 3). [35,36] Upon heating the solution, the signal for 3 diminishes in intensity and a new signal appeared at δ = 417.5 ppm…”

Optimization of the r2SCAN-3c Composite Electronic-Structure Method for Use with Slater-Type Orbital Basis Sets

“…In standard quantum chemical problems, the nonrelativistic Schrödinger equation is approximately solved to obtain the final wave function. However, relativistic effects can affect the molecular geometry as well as properties, especially when heavy atoms (typically with Z > 36) are present. − They can be included implicitly by relativistic effective core-potentials (ECPs) that replace the core electrons. This approach has the advantage of a lower computational cost and is sufficient for most chemical problems which mainly depend on valence electrons like thermochemisty .…”

Reducing Exact Two-Component Theory for NMR Couplings to a One-Component Approach: Efficiency and Accuracy

“…Nuclear magnetic resonance (NMR) spectroscopy is an indispensable tool for organic, inorganic, and organometallic chemistry. NMR spectra can be measured for almost all elements and provide important information about the chemical environment. − An accurate theoretical framework beyond the third row of the periodic table of elements necessitates the inclusion of special relativity. − For instance, it was shown that selenium and tin NMR spectra are substantially affected by relativistic effects. − This holds for both the chemical shift, describing the position of the signal, and the indirect spin–spin coupling constant (SSCC), describing the multiplet pattern.…”