Solid-State NMR Fermi Contact and Dipolar Shifts in Organometallic Complexes and Metalloporphyrins

Zhang, Yong; Sun, Hao; Oldfield, Eric

doi:10.1021/ja043461j

Cited by 57 publications

(71 citation statements)

References 18 publications

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“…21 This is basically the approach that we used previously to evaluate both solution and solid-state NMR hyperfine shifts, as well as other hyperfine (ESR, ENDOR) properties. 7,16,17,22 Spin densities were converted to hyperfine shifts by using the relation obtained previously: 7…”

Section: Computational Detailsmentioning

confidence: 99%

NMR Hyperfine Shifts in Blue Copper Proteins: A Quantum Chemical Investigation

Zhang

Oldfield

2008

J. Am. Chem. Soc.

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We present the results of the first quantum chemical investigations of 1 H NMR hyperfine shifts in the blue copper proteins (BCPs): amicyanin, azurin, pseudoazurin, plastocyanin, stellacyanin, and rusticyanin. We find that very large structural models that incorporate extensive hydrogen bond networks, as well as geometry optimization, are required to reproduce the experimental NMR hyperfine shift results, the best theory vs experiment predictions having R 2 = 0.94, a slope = 1.01, and a SD = 40.5 ppm (or ~4.7% of the overall ~860 ppm shift range). We also find interesting correlations between the hyperfine shifts and the bond and ring critical point properties computed using atoms-in-molecules theory, in addition to finding that hyperfine shifts can be well-predicted by using an empirical model, based on the geometry-optimized structures, which in the future should be of use in structure refinement.

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Section: Computational Detailsmentioning

confidence: 99%

NMR Hyperfine Shifts in Blue Copper Proteins: A Quantum Chemical Investigation

Zhang

Oldfield

2008

J. Am. Chem. Soc.

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“…via chemical bonds) and/or (ii) magnetic dipole-dipole coupling (i.e. via space) [8][9][10][11]. These result in the so-called paramagnetic effect: the NMR signal shows large broadening and a shift of the resonance frequency, which strongly reduces the efficiency of NMR spectroscopy (see, for example, the review by Bertini and Luchinat [8]).…”

Section: Introductionmentioning

confidence: 99%

Bulk magnetization and 1H NMR spectra of magnetically heterogeneous model systems

Levin¹,

Bud’ko²

2011

Journal of Magnetism and Magnetic Materials

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“…The field is more advanced for molecular calculations, which have successfully been used to assign the NMR spectra of a range of complexes of interest. [14][15][16][17] Recently, we reported the calculated and experimental NMR parameters for 1 (see Fig. 1).…”

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confidence: 99%

Calculation and experimental measurement of paramagnetic NMR parameters of phenolic oximate Cu(ii) complexes

Dawson

Mack

et al. 2017

Chem. Commun.

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We present a strategy for predicting the unusual 1 H and 13 C shifts in NMR spectra of paramagnetic bisoximato copper(II) complexes using DFT. We demonstrate good agreement with experimental measurements, although 1 H-13 C correlation spectra show that a combined experimental and theoretical approach remains necessary for full assignment.In recent years, paramagnetic NMR (or "pNMR") has developed greatly, with systems from metalloproteins 1 (dilute, isolated spins) to metal-organic frameworks 2-4 (denser networks of potentially coupled spins) and metal oxides 5 (very dense networks of highly coupled spins) being studied. For dilute spins, the NMR conditions can be selected such that the signal from nuclei near the paramagnetic centre is "invisible" owing to rapid relaxation and only the longer-range throughspace pseudocontact shifts are observed. 1 These are generally on the order of a few ppm and occur over distances such that the unpaired electron can be treated as a point spin, resulting in a simple 1/r 3 relationship with the shift. For dense spin networks such as transition metal oxides, it may be possible to assign the NMR spectra by analysis of bonding pathways (via oxygen). 5 However, in the intermediate regime, including materials such as catalytically-active transition metal complexes and metal-organic frameworks (MOFs), both the through-bond Fermi contact and through-space pseudocontact interactions affect the observed NMR spectrum and assignment can be both nontrivial and counterintuitive. 2,6-9 For example, in the 13 C NMR spectrum of the MOF HKUST-1 (Cu3btc2, btc = benzene-1,3,5-tricarboxylate), 10 the broadest resonance, shifted most by paramagnetic interactions, is not the carboxylate C (separated from Cu 2+ by just two bonds), but rather the adjacent quaternary C (three bonds from Cu). This assignment was confirmed using the relatively costly and timeconsuming approach of specific 13 C labelling in conjunction with 1 H-13 C cross polarisation (CP) NMR, which is generally inefficient for paramagnetic materials. 2 It would, therefore, be desirable to have a more general assignment method that does not rely on the development of bespoke synthetic pathways for efficient isotopic enrichment. Owing to the rapid MAS rates (necessitating the use of small rotors with, consequently, small sample volumes) required for highresolution pNMR spectra, sensitivity is inherently low and it would, therefore, also be advantageous to be able to predict shifts prior to the experimental measurement, particularly as resonances can be several hundred ppm away from their typical diamagnetic range.Periodic density functional theory (DFT) calculations have enjoyed great success in solid-state NMR, allowing the optimisation of experimental structures to an energy minimum and the subsequent calculation of highly accurate NMR parameters [11][12][13] However, pNMR DFT calculations are still in their relative infancy, particularly for periodic solids. The field is more advanced for molecular calculations, which have successfull...

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Solid-State NMR Fermi Contact and Dipolar Shifts in Organometallic Complexes and Metalloporphyrins

Cited by 57 publications

References 18 publications

NMR Hyperfine Shifts in Blue Copper Proteins: A Quantum Chemical Investigation

NMR Hyperfine Shifts in Blue Copper Proteins: A Quantum Chemical Investigation

Bulk magnetization and 1H NMR spectra of magnetically heterogeneous model systems

Calculation and experimental measurement of paramagnetic NMR parameters of phenolic oximate Cu(ii) complexes

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