Electron correlation and vibrational effects in predictions of paramagnetic NMR shifts

Abstract

Electronic structure calculations are fundamentally important for the interpretation of nuclear magnetic resonance (NMR) spectra from paramagnetic systems that include organometallic and inorganic compounds, catalysts, or metal-binding sites in proteins....

Paramagnetic Nuclear Magnetic Resonance Shifts for Triplet Systems and Beyond with Modern Relativistic Density Functional Methods

“…Based on the results for nickelocene, only the functionals BP86, , KT3, PBE, PBE0, , HSE06, – LC-ωPBE, ωB97X-D, B3LYP (VWN V-fit), ,, CAM-B3LYP, BH&HLYP, ,, PKZB, TPSS, TPSSh, , r 2 SCAN, , and LH20t are considered. It is noted that the EPR properties and thus the pNMR shifts are not substantially affected by the specific conformer for vanadocene, i.e., eclipsed vs staggered . We have verified that this also holds at the theoretical level in the present work for all metallocenes.…”

An Atomically Dispersed Mn-Photocatalyst for Generating Hydrogen Peroxide from Seawater via the Water Oxidation Reaction (WOR)

“…To provide further interpretation of the Mn′ and Mn″ components (Figure 3d,e), we created simplified models of possible environments surrounding the Mn 2+ ions in the Mn/AB-C 3 N 4 catalyst and energy-optimized them at the density functional theory (DFT) level (with the PBE0-D4 xc-functional, Grimme D4 correction, and the def2-TZVP basis set for Mn and def2-SVP for H, C, N, O; see Figure 3f). The 55 Mn A iso was subsequently calculated for each model at the coupled cluster level of theory with the DLPNO-CCSD approach 72,73 and the aug-cc-pVTZ-J basis set for Mn and EPR-II for H, C, N, O (Table S3). We note that state-ofthe-art coupled cluster calculations were necessary to provide reliable estimates of the EPR parameters.…”

“…We note that state-ofthe-art coupled cluster calculations were necessary to provide reliable estimates of the EPR parameters. Although DFT provides good structures and energetics, DFT is not capable of accurate predictions of EPR parameters in transition metal systems; 73 see Figure S7. With the predicted 55 Mn A iso values, we could correlate the Mn′ and Mn″ components to two distinct types of environments around the Mn 2+ ions present in the catalyst structure: the six-coordinated moiety represented by Models I/II with calculated 55 Mn A iso = −229 MHz, and the "edge" environment characterized by Model IV with calculated 55 Mn A iso = −258 MHz.…”

Computational NMR of the iron pyrazolylborate complexes [Tp2Fe]+ and Tp2Fe including solvation and spin-crossover effects

“…Only the BH signal is reproduced better by DLPNO-CCSD. In this comparison one must bear in mind that other factors, e.g., the presently omitted rovibrational effects 70 may disfavour the ab initio data in this case. The fact that the DLPNO-CCSD data are quasirelativistic, as opposed to the fully relativistic nature of the DFT data, also contributes to the differences.…”

“…This method has recently been applied with good results to HFC computations in pNMR by Jaworski and Hedin. 70…”