Since the first pioneering studies on small deuterated peptides dating more than 20 years ago, ¹H detection has evolved into the most efficient approach for investigation of biomolecular structure, dynamics, and interactions by solid-state NMR. The development of faster and faster magic-angle spinning (MAS) rates (up to 150 kHz today) at ultrahigh magnetic fields has triggered a real revolution in the field. This new spinning regime reduces the ¹H–¹H dipolar couplings, so that a direct detection of ¹H signals, for long impossible without proton dilution, has become possible at high resolution. The switch from the traditional MAS NMR approaches with ¹³C and ¹⁵N detection to ¹H boosts the signal by more than an order of magnitude, accelerating the site-specific analysis and opening the way to more complex immobilized biological systems of higher molecular weight and available in limited amounts. This paper reviews the concepts underlying this recent leap forward in sensitivity and resolution, presents a detailed description of the experimental aspects of acquisition of multidimensional correlation spectra with fast MAS, and summarizes the most successful strategies for the assignment of the resonances and for the elucidation of protein structure and conformational dynamics. It finally outlines the many examples where ¹H-detected MAS NMR has contributed to the detailed characterization of a variety of crystalline and noncrystalline biomolecular targets involved in biological processes ranging from catalysis through drug binding, viral infectivity, amyloid fibril formation, to transport across lipid membranes.

A combination of solid-state NMR methods for the extraction of ²³Na shift and quadrupolar parameters in the as-synthesized, structurally complex NaMnO₂ Na-ion cathode material, under magic-angle spinning (MAS) is presented. We show that the integration of the Magic-Angle Turning experiment with Rotor-Assisted Population transfer (RAPT) can be used both to identify shifts and to extract a range of magnitudes for their quadrupolar couplings. We also demonstrate the applicability of the two-dimensional one pulse (TOP) based double-sheared Satellite Transition Magic-Angle Spinning (TOP-STMAS) showing how it can yield a spectrum with separated shift and second-order quadrupolar anisotropies, which in turn can be used to analyze a quadrupolar lineshape free of anisotropic bulk magnetic susceptibility (ABMS) induced shift dispersion and determine both isotropic shift and quadrupolar products. Combining all these experiments, the shift and quadrupolar parameters for all observed Na environments were extracted and yielded excellent agreement with the density functional theory (DFT) based models that were reported in previous literature. We expect these methods to open the door for new possibilities for solid-state NMR to probe half-integer quadrupolar nuclei in paramagnetic materials and other systems exhibiting large shift dispersion.

Perovskite-type oxhydrides such as BaTiO_3−xH_y exhibit mixed hydride ion and electron conduction and are an attractive class of materials for developing energy storage devices. However, the underlying mechanism of electric conductivity and its relation to the composition of the material remains unclear. Here we report detailed insights into the hydride local environment, the electronic structure and hydride conduction dynamics of barium titanium oxyhydride. We demonstrate that DFT-assisted solid-state NMR is an excellent tool for differentiating between the different feasible electronic structures in these solids. Our results indicate that upon reduction of BaTiO₃ the introduced electrons are delocalized among all Ti atoms forming a bandstate. Furthermore, each vacated anion site is reoccupied by at most a single hydride, or else remains vacant. This single occupied bandstate structure persists at different hydrogen concentrations (y = 0.13–0.31) and a wide range of temperatures (∼100–300 K).

For paramagnetic species, it has been long understood that the hyperfine interaction between the unpaired electrons and the nucleus results in a nuclear magnetic resonance (NMR) peak that is shifted by a paramagnetic shift, rather than split by the coupling, due to an averaging of the electronic magnetic moment caused by electronic relaxation that is fast in comparison to the hyperfine coupling constant. However, although this feature of paramagnetic NMR has formed the basis of all theories of the param-agnetic shift, the precise theory and mechanism of the electronic relaxation required to predict this result has never been discussed, nor has the assertion been tested. In this paper, we show that the standard semi-classical Redfield theory of relaxation fails to predict a paramagnetic shift, as does any attempt to correct for the semi-classical theory using modifications such as the inhomogeneous master equation or Levitt & ndash;di Bari thermalization. In fact, only the recently-introduced Lindbladian theory of relaxation in magnetic resonance [J. Magn. Reson., 310, 106645 (2019)] is able to correctly predict the paramagnetic shift tensor and relaxation-induced linewidth in pNMR. Furthermore, this new formalism is able to pre-dict the NMR spectra of paramagnetic species outside the high-temperature and weak-order limits, and is therefore also applicable to dynamic nuclear polarization. The formalism is tested by simulations of five case studies, which include Fermi-contact and spin-dipolar hyperfine couplings, g-anisotropy, zero-field splitting, high and low temperatures, and fast and slow electronic relaxation.

Methanol is a liquid hydrogen carrier and potential platform molecule, and significant efforts are currently devoted to hydrogenate CO2 to methanol. In this work, hydrogenations of CO2 and captured CO2 (as dimethyl-carbamic acid, DMCA, and methylcarbamic acid, MCA) to methanol over Ru-MACHO (pre)catalysts were studied with a Ru-II-catalyst model by Density Functional Theory (DFT) calculations. For the hydrogenation of CO2, the concerted reaction was the rate-determining step involving a synchronous hydride transfer and proton transfer from the Ru-II-catalyst to coordinatively saturated intermediate methanediol. In the hydrogenation cycles of DMCA and MCA, the first hydride transfer reactions were more difficult than the concerted hydride and proton transfer from the Ru-II-catalyst to the aldehyde group of intermediate formaldehyde. These first hydride transfer reactions were identified as the rate-determining steps. The hydrogenations of DMCA and MCA were found much more favourable in methanol production than the direct CO2 hydrogenation, however, formamides could be main intermediate products due to the easier C-O breakage than C-N breakage in gem diols, and during the further hydrogenation of formamides, formaldehyde could be the main intermediate due to the easier C-N breakage than C-O breakage in alkanolamines. In all three hydrogenation cases, the amino (NH) ligand of the Ru-II-catalyst initially remained chemically innocent, and intermediates were stabilized by N-H center dot O hydrogenbonding interactions (HBIs) facilitating the continuation of catalytic hydrogenation cycles, but the NH ligand took part in multi-bond concerted reactions to produce eventually methanol.

Structural and morphological control of crystalline nanoparticles is crucial in the field of heterogeneous catalysis and the development of reaction specific catalysts. To achieve this, colloidal chemistry methods are combined with ab initio calculations in order to define the reaction parameters, which drive chemical reactions to the desired crystal nucleation and growth path. Key in this procedure is the experimental verification of the predicted crystal facets and their corresponding electronic structure, which in case of nanostructured materials becomes extremely difficult. Here, by employing P-31 solid-state nuclear magnetic resonance aided by advanced density functional theory calculations to obtain and assign the Knight shifts, we succeed in determining the crystal and electronic structure of the terminating surfaces of ultrafine Ni2P nanoparticles at atomic scale resolution. Our work highlights the potential of ssNMR nanocrystallography as a unique tool in the emerging field of facet-engineered nanocatalysts. Structural and morphological control of crystalline nanoparticles is crucial in heterogeneous catalysis. Applying DFT-assisted solid-state NMR spectroscopy, we determine the surface crystal and electronic structure of Ni2P nanoparticles, unveiling NMR nanocrystallography as an emerging tool in facet-engineered nanocatalysts.

We present a complete description of frequency-swept adiabatic pulses applied to isolated spin-1/2 nuclei with a shift anisotropy in solid materials under magic-angle spinning. Our theoretical framework unifies the existing descriptions of adiabatic pulses in the high-power regime, where the radiofrequency (RF) amplitude is greater than twice the spinning frequency, and the low-power regime, where the RF power is less than the spinning frequency, and so links the short high-powered adiabatic pulse (SHAP) and single-sideband-selective adiabatic pulses (S³AP) schemes used in paramagnetic solid-state NMR. We also identify a hitherto unidentified third regime intermediate between the low- and high-power regimes, and separated from them by rotary resonance conditions. We show that the prevailing benchmark of inversion performance based on (super) adiabatic factors is only applicable in the high- and intermediate-power regimes, but fails to account both for the poor performance at rotary resonance, and the impressive inversion seen in the low-power regime. For low-power pulses, which are non-adiabatic according to this definition of (super) adiabaticity, the effective Floquet Hamiltonian in the jolting frame reveals “hidden” (super) adiabaticity. The theory is demonstrated using a combination of simulation and experiment, and is used to refine the practical recommendations for the experimentalist who wishes to use these pulses.

Reactions of di(2-pyridyl) ketone, (py)(2)CO, with indium(III) halides in CH3NO2 have been studied, and a new transformation of the ligand has been revealed. In the presence of In-III, the C=O bond of (py)(2)CO is subjected to nucleophilic attack by the carbanion -:CH2NO2, yielding the dinuclear complexes [In2X4{(py)(2)C(CH2NO2)(O)}(2)] (X = Cl, 1; X = Br, 2; X = I, 3) in moderate to good yields. The alkoxo oxygens of the two eta(1):eta(2):eta(1)-(py)(2)C(CH2NO2)(O)- ligands doubly bridge the In-III centers and create a {In-2(mu(2)-OR)(2)}(4+) core. Two pyridyl nitrogens of different organic ligands and two terminal halogeno ions complete a distorted-octahedral stereochemistry around each In(III) ion. After maximum excitation at 360 or 380 nm, the solid chloro complex 1 emits blue light at 420 and 440 nm at room temperature, the emission being attributed to charge transfer within the coordinated organic ligand. Solid-state In-115 NMR spectra, in combination with DFT calculations, of 1-3 have been studied in detail at both 9.4 and 14.1 T magnetic fields. The nuclear quadrupolar and chemical shift parameters provide valuable findings concerning the electric field gradients and magnetic shielding at the nuclei of indium, respectively. The experimentally derived C-Q values are 40 +/- 3 MHz for 1, 46 +/- 5 MHz for 2, and 50 +/- 10 and 64 +/- 7 MHz for the two crystallographically independent InIII sites for 3, while the diso values fall in the range 130 +/- 30 to -290 +/- 60 ppm. The calculated C-Q and asymmetry parameter (eta(Q)) values are fully consistent with the experimental values for 1 and 2 and are in fairly good agreement for 3. The results have been analyzed and discussed in terms of the known (1, 3) and proposed (2) structural features of the complexes, demonstrating that In-115 NMR is an effective solid-state technique for the study of indium(III) complexes.

Highly active nickel phosphide (Ni₂P) nanoclusters confined in a mesoporous SiO₂ catalyst were synthesized by a two-step process targeting tight control over the Ni₂P size and phase. The Ni precursor was incorporated into the MCM-41 matrix by one-pot synthesis, followed by the phosphorization step, which was accomplished in oleylamine with trioctylphosphine at 300 °C so to achieve the phase transformation from Ni to Ni₂P. For benchmarking, Ni confined by the mesoporous SiO₂ (absence of phosphorization) and 11 nm Ni₂P nanoparticles (absence of SiO₂) was also prepared. From the microstructural analysis, it was found that the growth of Ni₂P nanoclusters was restricted by the mesoporous channels, thus forming ultrafine and highly dispersed Ni₂P nanoclusters (<2 nm). The above approach led to promising catalytic performance following the order u-Ni₂P@m-SiO₂ > n-Ni₂P > u-Ni@m-SiO₂ > c-Ni₂P in the selective hydrogenation of SO₂ to S. In particular, u-Ni₂P@m-SiO₂ exhibited SO₂ conversions of 94% at 220 °C and ∼99% at 240 °C, which are higher than the 11 nm stand-alone Ni₂P particles (43% at 220 °C and 94% at 320 °C), highlighting the importance of the role played by SiO₂ in stabilizing ultrafine nanoparticles of Ni₂P. The reaction activation energy E_a over u-Ni₂P@m-SiO₂ is ∼33 kJ/mol, which is lower than those over n-Ni₂P (∼36 kJ/mol) and c-Ni₂P (∼66 kJ/mol), suggesting that the reaction becomes energetically favored over the ultrafine Ni₂P nanoclusters.

Highly mesoporous SiO2-encapsulated NixPy crystals, where (x, y) = (5, 4), (2, 1), and (12, 5), were successfully synthesized by adopting a thermolytic method using oleylamine (OAm), trioctylphosphine (TOP), and trioctylphosphine oxide (TOPO). The Ni5P4@SiO2 system shows the highest reported activity for the selective hydrogenation of SO2 toward H2S at 320 degrees C (96% conversion of SO2 and 99% selectivity to H2S), which was superior to the activity of the commercial CoMoS@Al2O3 catalyst (64% conversion of SO2 and 71% selectivity to H2S at 320 degrees C). The morphology of the Ni5P4 crystal was finely tuned via adjustment of the synthesis parameters receiving a wide spectrum of morphologies (hollow, macroporous-network, and SiO2-confined ultrafine clusters). Intrinsic characteristics of the materials were studied by Xray diffraction, high-resolution transmission electron microscopy/scanning transmission electron microscopy-high-angle annular dark-field imaging, energydispersive X-ray spectroscopy, the Brunauer-Emmett-Teller method, H-2 temperature-programmed reduction, X-ray photoelectron spectroscopy, and experimental and calculated P-31 magic-angle spinning solid-state nuclear magnetic resonance toward establishing the structure-performance correlation for the reaction of interest. Characterization of the catalysts after the SO2 hydrogenation reaction proved the preservation of the morphology, crystallinity, and Ni/P ratio for all the catalysts.