Year-2008 nuclear quadrupole moments

Pyykkö, Pekka

doi:10.1080/00268970802018367

Cited by 455 publications

(518 citation statements)

References 106 publications

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“…We also considered the newer rangeseparated hybrid functionals. The long-range corrected LC-ωPBE, that has the correct asymptotic behaviour of the 30 exchange interaction, and the parameterized range-separated CAM-B3LYP hybrid functional give similar results and are in fact the best performers of all the DFT methods. For LC-ωPBE and CAM-B3LYP, the observed V zz values are reproduced with a MAE of 0.075-0.076 au, or ca.…”

Section: Scheme 1: Test Set For Efgs Of First-row Transition-metal Comentioning

confidence: 75%

“…47 In view of these limitations it is not surprising that the CCSD/QZVPP/6-31G** results are in worse agreement with experiment (MAE 0.12 au) than those from the hybrid DFT variants. Thus, the 30 latter are clearly the methods of choice for the computation of EFGs in transition-metal complexes.…”

Section: Scheme 1: Test Set For Efgs Of First-row Transition-metal Comentioning

confidence: 99%

“…Systematic DFT performance studies have fertilised computational transition-metal chemistry tremendously, 2 and will continue to do so as new functionals are constantly being developed. 30 Apart from geometries and energies, spectroscopic properties of transition-metal complexes are important targets for DFT. 3 A key quantity that can affect such spectroscopic observation (or, in fact, enable it in the first place) is the electric field gradient (EFG) at a quadrupolar nucleus.…”

Section: Introductionmentioning

confidence: 99%

“…25 Many experimental studies of the quadrupole interaction in transition metal complexes involve solid-state NMR spectroscopy. While this technique can often accurately determine the EFG parameters, the latter also encode long-range 30 intermolecular effects. As we want to assess the intrinsic accuracy of DFT methods for single molecules, gas-phase experimental data is therefore preferable as reference.…”

Section: Introductionmentioning

confidence: 99%

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Electric field gradients of transition metal complexes from density functional theory: assessment of functionals, geometries and basis sets

Björnsson

Bühl

2010

Dalton Trans.

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Electric field gradients (EFGs) were computed for the first-row transition metal nuclei in Cr(C 6 H 6 )(CO) 3 , MnO 3 F, Mn(CO) 5 H, MnCp(CO) 3 , Co(CO) 4 H, Co(CO) 3 (NO) and VCp(CO) 4 , for which experimental gas-phase data (in form of nuclear quadrupole coupling constants) are available from microwave spectroscopy. A variety of exchange-correlation functionals were assessed, 10 among which range-separated hybrids (such as CAM-B3LYP or LC-ωPBE) perform best, followed by global hybrids (such as B3LYP) and gradient-corrected functionals (such as BP86). While large basis sets are required on the metal atom for converged EFGs, smaller basis sets can be employed on the ligands. In most cases, EFGs show little sensitivity toward the geometrical parameters.

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Section: Scheme 1: Test Set For Efgs Of First-row Transition-metal Comentioning

confidence: 75%

Section: Scheme 1: Test Set For Efgs Of First-row Transition-metal Comentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electric field gradients of transition metal complexes from density functional theory: assessment of functionals, geometries and basis sets

Björnsson

Bühl

2010

Dalton Trans.

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“…The magnitude of the quadrupolar coupling constant is given by CQ = eQVZZ/h, where Q is the nuclear quadrupole moment (for which a value of 146.6 mB was used for 27 Al). 22 The asymmetry parameter is given by ηQ = (VXX − VYY)/VZZ.…”

Section: Dft Calculationsmentioning

confidence: 99%

An NMR crystallographic approach to monitoring cation substitution in the aluminophosphate STA-2

Seymour

Eschenroeder

Wright

et al. 2015

Solid State Nuclear Magnetic Resonance

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The substitution of the divalent cations Mg 2+ and Zn 2+ into the aluminophosphate (AlPO) framework of STA-2 has been studied using an "NMR crystallographic" approach, combining multinuclear solid-state NMR spectroscopy, X-ray diffraction and firstprinciples calculations. Although the AlPO framework itself is inherently neutral, the positive charge of the organocation template in an as-made material is usually balanced either by the coordination to the framework of anions from the synthesis solution, such as OH  or F  , and/or by the substitution of aliovalent cations. However, the exact position and distribution of the substituted cations can be difficult to determine, but can have a significant impact upon the catalytic properties a material exhibits once calcined.   For as-made Mg substituted STA-2, the positive charge of the organocation template is balanced by the substitution of Mg 2+ for Al 3+ and, where required, by hydroxide anions coordinated to the framework. 27 Al MAS NMR spectra show that Al is present in both tetrahedral and five-fold coordination, with the latter dependent on the amount of substituted cations, and confirms the bridging nature of the hydroxyl groups, while high-resolution MQMAS spectra are able to show that Mg appears to preferentially substitute on the Al1 site. This conclusion is also supported by first-principles calculations.The calculations also show that 31 P chemical shifts depend not only on the topologicallydistinct site in the SAT framework, but also on the number of next-nearest-neighbour Mg species, and the exact nature of the coordinated hydroxyls (whether the P atom forms part of a six-membered ring, P(OAl)2OH, where OH bridges between two Al atoms). The calculations demonstrate a strong correlation between the 31 P isotropic chemical shift and the average bond angle. In contrast, for Zn substituted STA-2, both X-ray diffraction and NMR spectroscopy show less preference for substitution onto Al1 or Al2, with both appearing to be present, although that into Al1 appears slightly more favoured.

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Quadrupolar Nuclei in Solids

Vega

2010

Encyclopedia of Magnetic Resonance

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Year-2008 nuclear quadrupole moments

Cited by 455 publications

References 106 publications

Electric field gradients of transition metal complexes from density functional theory: assessment of functionals, geometries and basis sets

Electric field gradients of transition metal complexes from density functional theory: assessment of functionals, geometries and basis sets

An NMR crystallographic approach to monitoring cation substitution in the aluminophosphate STA-2

Quadrupolar Nuclei in Solids

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