Vicinal tungsten-tungsten coupling constants in polyoxotungstates: DFT calculations challenge an empirical rule

Angewandte Chemie - International Edition

Volumn 44, Issue 13, 2005, Pages 2023-2026

  Bagno, Alessandro ^a   Bonchio, Marcello ^b  

^a UNIVERSITY OF PADOVA   (Italy)

^b INSTITUTE ON MEMBRANE TECHNOLOGY   (Italy)

Author keywords

Density functional calculations; NMR spectroscopy; Polyoxometalates; Spin spin coupling; Tungsten

Indexed keywords

CHEMICAL BONDS; COMPUTATIONAL METHODS; INORGANIC POLYMERS; NUCLEAR MAGNETIC RESONANCE; PROBABILITY DENSITY FUNCTION;

CORNER JUNCTIONS; COUPLING CONSTANT; POLYOXOMETALATES;

TUNGSTEN COMPOUNDS;

EID: 16844384718     PISSN: 14337851     EISSN: None     Source Type: Journal    
DOI: 10.1002/anie.200462292     Document Type: Article

References (26)

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10. C. R. Mayer, I. Fournier, R. Thouvenot, Chem. Eur. J. 2000, 6, 105-110. Coupling constants were reported for a similar derivative exhibiting very similar behavior to the POM discussed here.
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15. J. Autschbach, T. Ziegler in Calculation of NMR and EPR Parameters (Eds.: M. Kaupp, M. Bühl, V. G. Malkin), Wiley-VCH, Weinheim, 2004.
16. [9] We used double-ζ or triple-ζ basis sets, the latter with a single or double set of polarization functions on all atoms (DZ, TZP, and TZ2P, respectively), with frozen core orbitals where appropriate. Relativistic core potentials were generated with the Dirac utility.
17. [8]
18. See the Supporting Information for details. DSO, PSO, FC, and SD denote the diamagnetic and paramagnetic spin-orbit, Fermi contact, and spin-dipole contributions. All couplings are dominated by the FC term, which accounts for 90-95% of the total.
19. Only the DSO, PSO, and FC terms were calculated; the DSO term never exceeded 2 mHz.
20. Although most POMs bear remarkably large negative charges (up to -12), solvent effects on coupling constants are hardly known, consistent with their low charge density (q/m ratio; see X. López, C. Bo, J. M. Poblet, J. Am. Chem. Soc. 2002, 124, 12574-12582 for a discussion of its implications). Thus, isolated-ion modeling is probably suitable, despite the higher q/m of the model system. Work is in progress to address this issue.
21. WO and α values large negative values are predicted (see Supporting Information). However, this region is probably incompatible with the cage structures of POMs.
22. [9]
23. WO = 1.907 Å, α = 160° the calculated coupling decreased from 25 Hz to 23 Hz.
24. All basis sets of DZ quality. W: 4f shell frozen; O: 1s shell frozen; Si: 2p shell frozen. No core was frozen for H and Li.
25. The relative contributions of FC and PSO terms (Supporting Information) follow the same trend as the model system.
26. See the Supporting Information for details of bond lengths.