DFT Calculations of the <sup>183</sup>W NMR Chemical Shifts in Reduced Polyoxotungstates

The (183)W nuclear shielding in a variety of tungsten polyoxometalates (POM) (Lindqvist, Anderson, decatungstates, Keggin) of different shapes and charges has been modeled by DFT calculations that take into account relativistic effects, by means of the zero-order regular approximation (ZORA), and solvent effects, by the conductor-like screening model (COSMO) continuum method. The charge/surface area ratio (q/A) is proposed as an indicator of the charge density to which the solvation energies of all POMs are correlated in a satisfactory way. Among the various theoretical levels tested (ZORA scalar or spin-orbit, frozen-core or all-electron basis set, geometry optimization in the gas phase or in the continuum solvent, etc.), the best results are obtained when both geometry optimization in solvent and spin-orbit shielding are included (mean absolute error of delta=35 ppm). The quality of the computed chemical shifts depends systematically on the charge density as expressed by q/A; thus, POMs with low q/A ratios display the best agreement with experimental data. The performance of the method is such that computed values can aid the assignment of the (183)W NMR spectra of polyoxotungstates, as shown by the case of alpha-[PW(11)TiO(40)](5-), whose six signals are ranked computationally so as to almost reproduce the experimental ordering even though the signals are spaced by as little as 5 ppm.

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“…This had the additional advantage of being consistent with other related computational work on POMs 7. 9, 33, 34, 54–58…”

Section: Resultssupporting

confidence: 82%

“…Similar findings were recently reported by Poblet and Kazansky and their co‐workers 33. 34 All these observations consistently illustrate that solvation effects and the level of relativistic treatment play an important role. It was the purpose of this work to show how these problems can be overcome.…”

Section: Introductionsupporting

confidence: 90%

Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of ¹⁸³W NMR Chemical Shifts

Bagno

Bonchio

Autschbach

2006

Chemistry A European J

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“…This may be due to the slightly weak interaction between Re and its adjacent atoms compared with related bonds in PW 12 . As Poblet demonstrated that the reduction of a fully oxidized anion is accompanied by an expansion of the geometry, [33] the bonds in single-and double-electron reduced polyanions of PW 11 ReN are elongated. So, the reduced polyanions are loosened by adding reduced electrons.…”

Section: Resultsmentioning

confidence: 98%

A DFT Study on the Electronic and Redox Properties of [PW₁₁O₃₉(ReN)]^n–(n = 3, 4, 5) and [PW₁₁O₃₉(OsN)]^2–

et al. 2006

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“…In the present study we will make use of the previous experience [32][33][34][35] to find the best methodology for computing accurate d( 31 P) of solvated POMs. The task is even more complicated because POMs are negatively charged polyanions that must be modelled in the presence of a stabilising medium to accurately reproduce their features.…”

Section: Introductionmentioning

confidence: 99%

Accurate calculation of³¹P NMR chemical shifts in polyoxometalates

Pascual-Borràs

López

Poblet

2015

Phys. Chem. Chem. Phys.

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We search for the best density functional theory strategy for the determination of (31)P nuclear magnetic resonance (NMR) chemical shifts, δ((31)P), in polyoxometalates. Among the variables governing the quality of the quantum modelling, we tackle herein the influence of the functional and the basis set. The spin-orbit and solvent effects were routinely included. To do so we analysed the family of structures α-[P2W18-xMxO62](n-) with M = Mo(VI), V(V) or Nb(V); [P2W17O62(M'R)](n-) with M' = Sn(IV), Ge(IV) and Ru(II) and [PW12-xMxO40](n-) with M = Pd(IV), Nb(V) and Ti(IV). The main results suggest that, to date, the best procedure for the accurate calculation of δ((31)P) in polyoxometalates is the combination of TZP/PBE//TZ2P/OPBE (for NMR//optimization step). The hybrid functionals (PBE0, B3LYP) tested herein were applied to the NMR step, besides being more CPU-consuming, do not outperform pure GGA functionals. Although previous studies on (183)W NMR suggested that the use of very large basis sets like QZ4P were needed for geometry optimization, the present results indicate that TZ2P suffices if the functional is optimal. Moreover, scaling corrections were applied to the results providing low mean absolute errors below 1 ppm for δ((31)P), which is a step forward in order to confirm or predict chemical shifts in polyoxometalates. Finally, via a simplified molecular model, we establish how the small variations in δ((31)P) arise from energy changes in the occupied and virtual orbitals of the PO4 group.

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DFT Calculations of the ¹⁸³W NMR Chemical Shifts in Reduced Polyoxotungstates

Cited by 32 publications

References 35 publications

Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of ¹⁸³W NMR Chemical Shifts

Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of ¹⁸³W NMR Chemical Shifts

A DFT Study on the Electronic and Redox Properties of [PW₁₁O₃₉(ReN)]^n–(n = 3, 4, 5) and [PW₁₁O₃₉(OsN)]^2–

Accurate calculation of³¹P NMR chemical shifts in polyoxometalates

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DFT Calculations of the 183W NMR Chemical Shifts in Reduced Polyoxotungstates

Cited by 32 publications

References 35 publications

Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of 183W NMR Chemical Shifts

Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of 183W NMR Chemical Shifts

A DFT Study on the Electronic and Redox Properties of [PW11O39(ReN)]n–(n = 3, 4, 5) and [PW11O39(OsN)]2–

Accurate calculation of31P NMR chemical shifts in polyoxometalates

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DFT Calculations of the ¹⁸³W NMR Chemical Shifts in Reduced Polyoxotungstates

Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of ¹⁸³W NMR Chemical Shifts

Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of ¹⁸³W NMR Chemical Shifts

A DFT Study on the Electronic and Redox Properties of [PW₁₁O₃₉(ReN)]^n–(n = 3, 4, 5) and [PW₁₁O₃₉(OsN)]^2–

Accurate calculation of³¹P NMR chemical shifts in polyoxometalates