NMR mit Tischgeräten und deren Anwendungen von der Materialwissenschaft bis zur organischen Chemie

Monitoring Hydrogenation Reactions using Benchtop 2D NMR with Extraordinary Sensitivity and Spectral Resolution

Low-field benchtop nuclear magnetic resonance (BT-NMR) spectrometers with Halbach magnets are being increasingly used in science and industry as cost-efficient tools for the monitoring of chemical reactions, including hydrogenation. However, their use of low-field magnets limits both resolution and sensitivity. In this paper, we show that it is possible to alleviate these two problems through the combination of parahydrogen-induced polarization (PHIP) and fast correlation spectroscopy with time-resolved non-uniform sampling (TR-NUS). PHIP can enhance NMR signals so that substrates are easily detectable on BT-NMR spectrometers. The interleaved acquisition of one- and two-dimensional spectra with TR-NUS provides unique insight into the consecutive moments of hydrogenation reactions, with a spectral resolution unachievable in a standard approach. We illustrate the potential of the technique with two examples: the hydrogenation of ethylphenyl propiolate and the hydrogenation of a mixture of two substrates - ethylphenyl propiolate and ethyl 2-butynoate.

Cultural Heritage Studies with Mobile NMR

Nuclear magnetic resonance (NMR) provides in situ information about selected isotope densities in samples and objects, while also providing contrast through rotational and translational molecular dynamics. These parameters are probed not only in NMR spectroscopy and imaging but also in nondestructive materials testing by mobile stray-field NMR, the unique properties of which are valuable in cultural heritage studies. We present recent progress in the analysis of cultural heritage with mobile ¹ H NMR stray-field sensors, for which the detection zone is outside of the NMR magnet. Prominent applications include the analysis of stratigraphies in paintings and frescoes, and the assessment of material states changing under the impact of aging, conservation, and restoration.