The Presumption of Innocence? A DFT-Directed Verdict on Oxidized Amavadin and Vanadium Catecholate Complexes

Geethalakshmi, K. R.; Waller, Mark P.; Bühl, Michæl

doi:10.1021/ic701650y

Cited by 20 publications

(49 citation statements)

References 62 publications

(102 reference statements)

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“…Similar behavior was reported in a previous study of vanadium complexes with oxyamine ligands where substantial errors were observed for δ zz , the chemical shift component perpendicular to the oxyamine plane. 24, 32 The fact that even at this level of theory difficulties are encountered in describing the interaction between the three-membered oxyamine-vanadium is consistent with the well-known problems with calculations of these strained compounds. The lower calculated anisotropies suggest that the molecule is less symmetric than the models used and indicate that the calculations underestimate the bonding between the vanadium and the oxyamine unit when using the X-ray structures.…”

Section: Resultssupporting

confidence: 61%

“…17, 18, 23, 24, 32, 38–42 Table 1 contains the results of calculations performed on the HIDA and HIDPA complexes using three functionals, b3lyp, PBE1PBE, and PBEPBE, and three basis sets, 6–311++G(d,p), 6–311++G, and tzvp as available in the Gaussian03 program. 43 The results obtained for the quadrupolar coupling constant and the asymmetry parameters of the EFG tensor for the HIDPA complex are in good agreement with experiment.…”

Section: Resultsmentioning

confidence: 99%

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51V solid-state NMR and density functional theory studies of eight-coordinate non-oxo vanadium complexes: oxidized amavadin

et al. 2009

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SUMMARY Using 51V magic angle spinning solid-state NMR spectroscopy and Density Functional Theory calculations we have characterized the chemical shift and quadrupolar coupling parameters for two eight-coordinate vanadium complexes, [PPh4][V(V)(HIDPA)2] and [PPh4][V(V)(HIDA)2]; HIDPA = 2,2′-(hydroxyimino)dipropionate and HIDA = 2,2′-(hydroxyimino)diacetate. The coordination geometry under examination is the less common non-oxo eight coordinate distorted dodecahedral geometry that has not been previously investigated by solid-state NMR spectroscopy. Both complexes were isolated by oxidizing their reduced forms: [V(IV)(HIDPA)2]2- and [V(IV)(HIDA)2]2-. V(IV)(HIDPA)22- is also known as amavadin, a vanadium-containing natural product present in the Amanita muscaria mushroom and responsible for vanadium accumulation in nature. The quadrupolar coupling constants, CQ, are found to be moderate, 5.0 to 6.4 MHz while the chemical shift anisotropies are relatively small for vanadium complexes, −420 and 360 ppm. The isotropic chemical shifts in the solid state are −220 and −228 ppm for the two compounds, and near the chemical shifts observed in solution. Presumably this is a consequence of the combined effects of the increased coordination number and the absence of oxo groups. Density Functional Theory calculations of the electric field gradient parameters are in good agreement with the NMR results while the chemical shift parameters show some deviation from the experimental values. Future work on this unusual coordination geometry and a combined analysis by solid-state NMR and Density Functional Theory should provide a better understanding of the correlations between experimental NMR parameters and the local structure of the vanadium centers.

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Section: Resultssupporting

confidence: 61%

Section: Resultsmentioning

confidence: 99%

51V solid-state NMR and density functional theory studies of eight-coordinate non-oxo vanadium complexes: oxidized amavadin

et al. 2009

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“…Moreover, in this calculation, the principal components of the computed CSA tensor are also in reasonable agreement with the experiment ( δ σ agrees to within 90 ppm, and η σ –to within 0.04) and the computed values are similar to the previously reported calculations conducted at a comparable level of theory. 66 …”

Section: Resultsmentioning

confidence: 99%

“…66 DFT calculations generally predict the NMR parameters accurately. However, when a ligand is non-innocent with large 51 V isotropic chemical shifts, the experimentally observed de-shielding is less well described.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Noninnocent Metal Complexes Using Solid-State NMR Spectroscopy: o-Dioxolene Vanadium Complexes

et al. 2011

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51V solid-state NMR (SSNMR) studies of a series of non-innocent vanadium(V) catechol complexes have been conducted to evaluate the possibility that 51V NMR observables, quadrupolar and chemical shift anisotropies, and electronic structures of such compounds can be used to characterize these compounds. The vanadium(V) catechol complexes described in these studies have relatively small quadrupolar coupling constants, which cover a surprisingly small range from 3.4 to 4.2 MHz. On the other hand, isotropic 51V NMR chemical shifts cover a wide range from −200 ppm to 400 ppm in solution and from −219 to 530 ppm in the solid state. A linear correlation of 51V NMR isotropic solution and solid-state chemical shifts of complexes containing non-innocent ligands is observed. These experimental results provide the information needed for the application of 51V SSNMR spectroscopy in characterizing the electronic properties of a wide variety of vanadium-containing systems, and in particular those containing non-innocent ligands and that have chemical shifts outside the populated range of −300 ppm to −700 ppm. The studies presented in this report demonstrate that the small quadrupolar couplings covering a narrow range of values reflect the symmetric electronic charge distribution, which is also similar across these complexes. These quadrupolar interaction parameters alone are not sufficient to capture the rich electronic structure of these complexes. In contrast, the chemical shift anisotropy tensor elements accessible from 51V SSNMR experiments are a highly sensitive probe of subtle differences in electronic distribution and orbital occupancy in these compounds. Quantum chemical (DFT) calculations of NMR parameters for [VO(hshed)(Cat)] yield 51V CSA tensor in reasonable agreement with the experimental results, but surprisingly, the calculated quadrupolar coupling constant is significantly greater than the experimental value. The studies demonstrate that substitution of the catechol ligand with electron donating groups results in an increase in the HOMO-LUMO gap and can be directly followed by an upfield shift for the vanadium catechol complex. In contrast, substitution of the catechol ligand with electron withdrawing groups results in a decrease in the HOMO-LUMO gap and can directly be followed by a downfield shift for the complex. The vanadium catechol complexes were used in this work because the 51V is a half-integer quadrupolar nucleus whose NMR observables are highly sensitive to the local environment. However, the results are general and could be extended to other redox active complexes that exhibit similar coordination chemistry as the vanadium catechol complexes.

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Nuclear Magnetic Resonance (NMR) Parameters of Transition Metal Complexes: Methods and Applications

Kaupp

Bühl

2005

Encyclopedia of Inorganic Chemistry

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This article provides an overview of first‐principle computations targeted at nuclear magnetic resonance (NMR) properties of transition‐metal complexes. Recent methodological developments and illustrative applications are highlighted, all of which are rooted in density functional theory (DFT). Special attention is called to chemical applications of such NMR computations, ranging from structure elucidation of metalloenzymes to detailed interpretation of NMR spectra of paramagnetic compounds.

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The Presumption of Innocence? A DFT-Directed Verdict on Oxidized Amavadin and Vanadium Catecholate Complexes

Cited by 20 publications

References 62 publications

51V solid-state NMR and density functional theory studies of eight-coordinate non-oxo vanadium complexes: oxidized amavadin

51V solid-state NMR and density functional theory studies of eight-coordinate non-oxo vanadium complexes: oxidized amavadin

Characterization of Noninnocent Metal Complexes Using Solid-State NMR Spectroscopy: o-Dioxolene Vanadium Complexes

Nuclear Magnetic Resonance (NMR) Parameters of Transition Metal Complexes: Methods and Applications

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