The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra

We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio frequency, can be obtained from solid samples. Experimental results are shown for static and magic-angle spinning conditions. In addition, a tuning procedure based on the probes’ NMR noise characteristics and similar to the one described previously for liquids probes can also be used to optimize signal-to-noise ratios in 1H-MAS experiments.

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“…Similarly, large tuning offsets have been reported recently by Rossini et al [14] for optimized NQR spectra of 75 As and 35 Cl.…”

Section: Resultssupporting

confidence: 78%

Observation of NMR noise from solid samples

Schlagnitweit

Dumez

Nausner

et al. 2010

Journal of Magnetic Resonance

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“…This approach was in many instances easier to implement than measuring the reception tuning sensitivity directly, especially for samples containing large signals (such as those from bulk H 2 O), where solvent suppression techniques are difficult to implement reproducibly over a range of tuning conditions. Examples of this tuning procedure have been shown in both ambient temperature and cryogenically cooled probes 6,7, as well as with hyperpolarized spins 10,11 and with solid-state NMR probes 7,8. In that work, the appearance of a symmetrical “dip” spin-noise line shape was seen as the condition for optimal detection.…”

Section: Introductionmentioning

confidence: 93%

“…In related experiments, it was found that the tuning conditions for optimal transmission vs. optimal reception could differ significantly for different NMR probes 2,6–8. We refer to spin-noise as the process of spontaneous emission of signals by the spin system, and absorbed circuit noise as the process of absorption of circuit noise by the spin system.…”

Section: Introductionmentioning

confidence: 99%

Dependence of NMR noise line shapes on tuning, matching, and transmission line properties

Bendet-Taicher

Müller

Jerschow

2014

Concepts Magn Reson

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The tuning and matching conditions of rf circuits, as well as the properties of the transmission lines connecting these to the preamplifier, have direct consequences for NMR probe sensitivity and as for the optimum delivery of rf power to the sample. In addition, tuning/matching conditions influence radiation damping effects, which manifest themselves as fast signal flip-back and line broadening effects, and can lead to concentration-dependent frequency shifts. Previous studies have also shown that the appearance of spin-noise and absorbed circuit noise signals heavily depended on tuning settings. Consequently, all these phenomena are linked together. The mutual connections and interdependences of these effects are highlighted and reviewed here.

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“…It is highly desirable to have a priori knowledge of the approximate parameters, as this drastically reduces the otherwise lengthy time spent searching for NQR frequencies. Broadband frequency swept pulses may be utilized to expedite the location of NQR resonances,81 using WURST echo82 or WURST‐QCPMG56, 57 pulse sequences. In many cases, 35 Cl SSNMR and NQR spectroscopy can be used in conjunction with one another: the former for obtaining approximate values of C Q and η Q , and the latter for the identification of multiple sites with similar quadrupolar parameters and the refinement of C Q .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Cembranoid Analogues through Ring‐Closing Metathesis of Terpenoid Precursors: A Challenge Regarding Ring‐Size Selectivity

Heidt

Baro

Köhn

2015

Chemistry A European J

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A systematic study on ring-closing metathesis with Grubbs II catalyst to cembranoid macrocycles is described. Acyclic terpenoids with a functional group X in the homoallylic position relative to an RCM active terminus and substituents R, R(1) directly attached to the other terminal double bond were prepared from geraniol derived trienes and fragments that are based on bromoalkenes and dimethyl malonate. Such terpenoids were suitable precursors, despite the presence of competing double bonds in their framework. The size of R and R(1) is crucial for successful macrocyclization. Whereas small alkyl substituents at the double bond directed the RCM towards six-membered ring formation, cross metathesis leading to dimers dominated for bulkier alkyl groups. A similar result was obtained for precursors without functional group X. In the case of unsymmetrically substituted terpenoid precursor (R = Et, R(1) = Me) with homoallylic OTBS or OMe group, the RCM could be controlled towards formation of macrocyclic cembranoids, which were isolated with excellent E-selectivity. The role of the substituents was further studied by quantum chemical calculations of simplified model substrates. Based on these results a mechanistic rationale is proposed.

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The application of frequency swept pulses for the acquisition of nuclear quadrupole resonance spectra

Cited by 24 publications

References 75 publications

Observation of NMR noise from solid samples

Observation of NMR noise from solid samples

Dependence of NMR noise line shapes on tuning, matching, and transmission line properties

Synthesis of Cembranoid Analogues through Ring‐Closing Metathesis of Terpenoid Precursors: A Challenge Regarding Ring‐Size Selectivity

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