Natural-Abundance Solid-State ²H NMR Spectroscopy at High Magnetic Field

Abstract

High-resolution solid-state (2)H NMR spectroscopy provides a method for measuring (1)H NMR chemical shifts in solids and is advantageous over the direct measurement of high-resolution solid-state (1)H NMR spectra, as it requires only the application of routine magic angle sample spinning (MAS) and routine (1)H decoupling methods, in contrast to the requirement for complex pulse sequences for homonuclear (1)H decoupling and ultrafast MAS in the case of high-resolution solid-state (1)H NMR. However, a significant obstacle to the routine application of high-resolution solid-state (2)H NMR is the very low natural abundance of (2)H, with the consequent problem of inherently low sensitivity. Here, we explore the feasibility of measuring (2)H MAS NMR spectra of various solids with natural isotopic abundances at high magnetic field (850 MHz), focusing on samples of amino acids, peptides, collagen, and various organic solids. The results show that high-resolution solid-state (2)H NMR can be used successfully to measure isotropic (1)H chemical shifts in favorable cases, particularly for mobile functional groups, such as methyl and -N(+)H(3) groups, and in some cases phenyl groups. Furthermore, we demonstrate that routine (2)H MAS NMR measurements can be exploited for assessing the relative dynamics of different functional groups in a molecule and for assessing whole-molecule motions in the solid state. The magnitude and field-dependence of second-order shifts due to the (2)H quadrupole interaction are also investigated, on the basis of analysis of simulated and experimental (1)H and (2)H MAS NMR spectra of fully deuterated and selectively deuterated samples of the α polymorph of glycine at two different magnetic field strengths.

High-Resolution Solid-State2H NMR Spectroscopy of Polymorphs of Glycine

“…Similar differences in the distribution of intensities and linewidths between the α and γ polymorphs are also observed in the 2 H MAS NMR spectra recorded at MAS frequency 14 kHz (Figure ). Previously, it has been suggested that the line broadening observed in the 2 H MAS NMR spectrum of the γ polymorph may be due to the frequency of the reorientational motion of the −N + D 3 group , approaching the same order of magnitude as the static 2 H quadrupole coupling constant.…”

“…The measurement of high-resolution 2 H NMR spectra for solids is substantially more straightforward than measurement of the corresponding 1 H NMR spectra, as 2 H NMR spectra can be recorded using standard heteronuclear 1 H decoupling and magic angle sample spinning (MAS). − The only significant drawback of solid-state 2 H NMR arises from the very low natural abundance of the 2 H isotope (∼0.0115%), and the inherently low sensitivity of the technique dictates that isotopic labeling of materials for 2 H NMR studies of solids is usually necessary, although progress has also been made in recording solid-state 2 H NMR spectra for materials with natural isotopic abundance. Thus, we have shown recently that natural-abundance solid-state 2 H NMR spectroscopy can be applied successfully to study structural and dynamic properties of solids …”

Temperature-Dependent Structural Properties, Phase Transition Behavior, and Dynamic Properties of a Benzene Derivative in the Solid State

“…In the present work, we have recorded the 2 H NMR spectrum for a sample of DBTMB with natural isotopic abundances. As described elsewhere, − given the very low natural abundance of the 2 H isotope (0.015%), it is advantageous to record the 2 H NMR spectrum for natural-abundance samples under conditions of magic-angle sample spinning (MAS; the frequency of MAS is denoted ν r ). Under such circumstances, the broad-line 2 H NMR powder pattern is split into a set of narrow peaks separated by the spinning frequency ν r , with the overall intensity envelope reflecting, at least approximately, the intensity distribution of the 2 H NMR powder pattern.…”

“…In the present work, we have recorded the 2 H NMR spectrum for a sample of DBTMB with natural isotopic abundances. As described elsewhere, [49][50][51][52][53][54][55][56][57] given the very low natural abundance of The natural-abundance solid-state 2 H NMR spectrum of DBTMB recorded at ambient temperature (25 °C) with MAS at νr = 2 kHz is shown in Figure 7a. The intensity distribution of the spinning sidebands is very similar to that observed previously in the same type of 2 H NMR measurement at the same MAS frequency for a sample of hexamethylbenzene with natural isotopic abundances.…”

Physical methods and techniques NMR spectroscopy

“…10). 78 Double-quantum (DQ) natural abundance 1 H-1 H combined rotation and multiple-pulse spectroscopy (CRAMPS) solid-state NMR correlation spectra, have determined ribbon-like and quartet-like self-assembly structure for guanosine crystals that were not suitable for X-ray diffraction. Distinct resonances and DQ peaks were assigned by means of gauge-including projector-augmented wave (GIPAW) chemical shift calculations.…”