High-field QCPMG NMR of large quadrupolar patterns using resistive magnets

Hung, Ivan; Shetty, Kiran Kumar; Ellis, Paul D.; Brey, Wallace S.; Gan, Zhehong

doi:10.1016/j.ssnmr.2009.10.001

Cited by 19 publications

(12 citation statements)

References 52 publications

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“…[98][99][100][101][102][103] Recently, 35 Cl UW NMR experiments have been applied to study chlorine atoms in terminal and bridging bonding environments in transition metal complexes, as well as in terminal carbon-chlorine bonds in organic molecules, where powder patterns can be over several MHz in breadth. 41,[104][105][106][107][108][109] -25-The 35 Cl SSNMR spectra for all compounds are shown in Figure 6 and the corresponding EFG tensor parameters are presented in Table 3. The 35 Cl NMR powder pattern for Pt(NH 3 ) Figure S12).…”

Section: Resultsmentioning

confidence: 99%

Unravelling the Structure of Magnus’ Pink Salt

Lucier

Johnston

et al. 2014

J. Am. Chem. Soc.

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A combination of multinuclear ultra-wideline solid-state NMR, powder X-ray diffraction (pXRD), X-ray absorption fine structure experiments, and first principles calculations of platinum magnetic shielding tensors has been employed to reveal the previously unknown crystal structure of Magnus' pink salt (MPS), [Pt(NH3)4][PtCl4], study the isomeric Magnus' green salt (MGS), [Pt(NH3)4][PtCl4], and examine their synthetic precursors K2PtCl4 and Pt(NH3)4Cl2·H2O. A simple synthesis of MPS is detailed which produces relatively pure product in good yield. Broad (195)Pt, (14)N, and (35)Cl SSNMR powder patterns have been acquired using the WURST-CPMG and BRAIN-CP/WURST-CPMG pulse sequences. Experimentally measured and theoretically calculated platinum magnetic shielding tensors are shown to be very sensitive to the types and arrangements of coordinating ligands as well as intermolecular Pt-Pt metallophilic interactions. High-resolution (195)Pt NMR spectra of select regions of the broad (195)Pt powder patterns, in conjunction with an array of (14)N and (35)Cl spectra, reveal clear structural differences between all compounds. Rietveld refinements of synchrotron pXRD patterns, guided by first principles geometry optimization calculations, yield the space group, unit cell parameters, and atomic positions of MPS. The crystal structure has P-1 symmetry and resides in a pseudotetragonal unit cell with a distance of >5.5 Å between Pt sites in the square-planar Pt units. The long Pt-Pt distances and nonparallel orientation of Pt square planes prohibit metallophilic interactions within MPS. The combination of ultra-wideline NMR, pXRD, and computational methods offers much promise for future investigation and characterization of Pt-containing systems.

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Section: Resultsmentioning

confidence: 99%

Unravelling the Structure of Magnus’ Pink Salt

Lucier

Johnston

et al. 2014

J. Am. Chem. Soc.

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“…The sources of field fluctuations in resistive magnets were characterized and progress was made toward ameliorating them [10]. The remarkable possibilities of high fields for reducing broadening in the spectra of half-integer quadrupolar nuclei was explored in resistive magnets [14, 15, 17]. The Keck Foundation supported the development of a 25 T magnet at the NHMFL for chemical applications of NMR and EPR [9, 19, 20].…”

Section: Sch Magnetmentioning

confidence: 99%

“…The Keck magnet achieved a homogeneity of 48 ppm which was corrected to 12 ppm with the addition of ferromagnetic shims. The utility of a resistive magnet such as the Keck for wide line NMR was demonstrated [15] and pulse techniques to take advantage of the high field of this resistive magnet for high resolution NMR have been explored [12, 16]. The limitations of both stability and homogeneity, however, led to the Keck magnet serving as a test facility for further improvements in field homogeneity and suppression of field fluctuations [21] rather than as a tool for routine high-field NMR investigations.…”

Section: Sch Magnetmentioning

confidence: 99%

NMR spectroscopy up to 35.2 T using a series-connected hybrid magnet

Gan

Hung

Wang

et al. 2017

Journal of Magnetic Resonance

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The National High Magnetic Field Laboratory has brought to field a Series-Connected Hybrid magnet for NMR spectroscopy. As a DC powered magnet it can be operated at fields up to 36.1 T. The series connection between a superconducting outsert and a resistive insert dramatically minimizes the high frequency fluctuations of the magnetic field typically observed in purely resistive magnets. Current-density-grading among various resistive coils was used for improved field homogeneity. The 48 mm magnet bore and 42 mm outer diameter of the probes leaves limited space for conventional shims and consequently a combination of resistive and ferromagnetic shims are used. Field maps corrected for field instabilities were obtained and shimming achieved better than 1 ppm homogeneity over a cylindrical volume of 1 cm diameter and height. The magnetic field is regulated within 0.2 ppm using an external 7Li lock sample doped with paramagnetic MnCl2. The improved field homogeneity and field regulation using a modified AVANCE NEO console enables NMR spectroscopy at 1H frequencies of 1.0, 1.2 and 1.5 GHz. NMR at 1.5 GHz reflects a 50% increase in field strength above the highest superconducting magnets available presently. Three NMR probes have been constructed each equipped with an external lock rf coil for field regulation. Initial NMR results obtained from the SCH magnet using these probes illustrate the very exciting potential of ultra-high magnetic fields.

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“…CPMG acquisition has also proven beneficial in combination with magic angle spinning (MAS) [68,69] and two-dimensional experiments, such as magic-angle-turning [70] and multiple-quantum correlation techniques [20,26,27,[71][72][73][74]. In addition, it has recently been shown that the rapid cyclical refocusing of QCPMG makes it an ideal experiment for application in powered resistive magnets due to its reduced sensitivity to field inhomogeneity and instability [75].…”

Section: Introductionmentioning

confidence: 99%