Solid-state 2H NMR Spectroscopy Research Articles

Mayenite-Based Electride C12A7e−: A Reactivity and Stability Study

Ru supported on mayenite electride, [Ca24Al28O64]4+(e−)4 a calcium aluminum oxide denoted as C12A7e−, are described in the literature as highly active catalysts for ammonia synthesis, especially under conditions of low absolute pressure. In this study, we investigated the application of recently reported plasma arc melting synthesized C12A7e− (aluminum solid reductant) as supports of Ru/C12A7e− catalysts in ammonia synthesis up to pressures of 7.6 MPa. Together with the plasma-arc-melting-based catalyst support, we investigated a similar plasma-synthesized C12A7e− (graphite solid reductant) and a vacuum-sintering-based C12A7e−. Complementary to the catalytic tests, we applied 2H solid-state NMR spectroscopy, DRUVVis-spectroscopy, thermal analysis and PXRD to study and characterize the reactivity of different plasma-synthesized and vacuum-sintered C12A7e− towards H2/D2 and H2O. The catalysts showed an immediate deactivation at pressures > 1 MPa, which can be explained by irreversible hydride formation at higher pressures, as revealed by reactivity tests of C12A7e− towards H2/D2. The direct formation of C12A7:D from C12A7e− is proven. It can be concluded that the application of Ru/C12A7e− catalysts at the industrial scale has limited prospects due to irreversible hydride formation at relevant pressures > 1 MPa. Furthermore, we report an in-depth study relating to structural changes in the material in the presence of H2O.

Membrane Deformation Modulated by Hydration and Cholesterol Unveiled by Solid-State 2H NMR Spectroscopy

Phospholipid membranes are biological liquid crystals in which intermolecular interactions at mesoscopic length scales play key roles in the emergence of membrane physical properties like structure and rigidity. Such interactions modulated by membrane hydration [1] and cholesterol [2] have been investigated using solid-state 2H NMR spectroscopy. The average structure is manifested by the lineshapes through principal values of static or residual coupling tensors due to quadrupolar interactions. The residual quadrupolar couplings (RQCs) yield segmental order parameters for the individual acyl segments (i), providing average membrane properties such as bilayer thickness, area/lipid, and spontaneous curvature [3]. We show that membrane dehydration and increased cholesterol content result in greater RQCs, indicative of membrane thickening. Elastic membrane deformations are exhibited as collective order-director fluctuations (ODF) contributing to the nuclear magnetic relaxation. At mesoscopic length scales the thermal fluctuations connect to membrane mechanical properties via the fluctuation-dissipation theorem. Model-free interpretation of the functional dependence of spin-lattice relaxation rates, R1Z, on segmental order parameters (square-law) reveals emergent material properties in the liquid-crystalline state. The R1Z relaxation dispersion and temperature dependence of square-law plots indicate a nematic-like membrane hydrocarbon core. Solid-state 2H NMR relaxation studies demonstrate that both dehydration and increased cholesterol content in the membrane lead to decreased slopes of square-law plots, indicating an increase in membrane bending rigidity, consistent with neutron spin-echo (NSE) measurements. Analogous 2H NMR studies with various membrane lipid compositions and peptide-reconstituted membranes have addressed lipid-mediated cell signaling and lipid-protein interactions. Molecular dynamics simulations provide further insights on the correspondence of the solid-state NMR and NSE results. [1] K.J. Mallikarjunaiah et al. (2019) Phys. Chem. Chem. Phys. 21, 18422. [2] S. Chakraborty et al. (2020) Proc. Natl. Acad. Sci. 117, 21896. [3] Mallikarjunaiah et al. (2011) Biophys. J. 100, 98.

Heterogeneous Polymer Dynamics Explored Using Static 1H NMR Spectra.

NMR spectroscopy continues to provide important molecular level details of dynamics in different polymer materials, ranging from rubbers to highly crosslinked composites. It has been argued that thermoset polymers containing dynamic and chemical heterogeneities can be fully cured at temperatures well below the final glass transition temperature (Tg). In this paper, we described the use of static solid-state 1H NMR spectroscopy to measure the activation of different chain dynamics as a function of temperature. Near Tg, increasing polymer segmental chain fluctuations lead to dynamic averaging of the local homonuclear proton-proton (1H-1H) dipolar couplings, as reflected in the reduction of the NMR line shape second moment (M2) when motions are faster than the magnitude of the dipolar coupling. In general, for polymer systems, distributions in the dynamic correlation times are commonly expected. To help identify the limitations and pitfalls of M2 analyses, the impact of activation energy or, equivalently, correlation time distributions, on the analysis of 1H NMR M2 temperature variations is explored. It is shown by using normalized reference curves that the distributions in dynamic activation energies can be measured from the M2 temperature behavior. An example of the M2 analysis for a series of thermosetting polymers with systematically varied dynamic heterogeneity is presented and discussed.

Microfluidic synthesis of monodisperse porous polystyrene microspheres for sorption of bovine serum albumin

Droplet microfluidics offers exquisite control over the flows of multiple fluids in micro-scale, enabling fabrication of advanced microspheres with precisely tuneable structures. The main goal of this work was to design monodispersed carboxylated polystyrene microspheres with a developed pore structure (a specific surface area more than 200 m2/g) using microfluidic technology. We investigated the influence of the composition of monomer phase for the stable formation of droplets. Under the stable region, the resulting microspheres (with diameter 50 µm) showed narrow size distribution having a coefficient of variation of below 2%. The obtained microspheres are characterised by morphology and surface structure by means of electron microscopy. The structure of cross-linked microspheres is investigated by solid-state 1H NMR spectroscopy. Finally, these microspheres have great potential for the effective sorption of biologically active substances (bovine serum albumin).

Enhanced Rotation by Ground State Destabilization in Amphidynamic Crystals of a Dipolar 2,3-Difluorophenylene Rotator as Established by Solid State 2H NMR and Dielectric Spectroscopy

We report the synthesis and rotational dynamics of the pillared metal–organic framework Zn2(F2BDC)2(DABCO) where F2BDC = 2,3-difluorobenzene-1,4-dicarboxylate acts as a rotating dipolar linker and DABCO = 1,4-diazabicyclo[2.2.2]octane acts as a spacer (F2MOF 1). The pillared structure of F2MOF 1 was confirmed by X-ray diffraction and CP-MAS 13C NMR analyses. Using variable temperature solid state 2H NMR and broadband dielectric spectroscopy, we characterized the rotational dynamics of the dipolar F2BDC linker in the solid state. Variable temperature (VT) quadrupolar echo 2H NMR measurements revealed a rotational activation energy of Ea = 6.8 ± 0.1 kcal/mol, which agreed well with temperature- and frequency-dependent dielectric measurements, indicating a barrier of Ea = 7.1 ± 0.5 kcal/mol. Structural data from single crystal X-ray diffraction and quantum mechanical calculations (DFT) suggest that the rotational potential is determined by steric interactions between the dipolar rotator and the stator linkers such that fluorine atoms in the F2BDC linker reduce the activation energy by destabilization of the coplanar BDC ground state.

Vitamin E - phosphatidylethanolamine interactions in mixed membranes with sphingomyelin: Studies by 2H NMR

Among the structurally diverse collection of lipids that comprise the membrane lipidome, polyunsaturated phospholipids are particularly vulnerable to oxidation. The role of α-tocopherol (vitamin E) is to protect this influential class of membrane phospholipid from oxidative damage. Whether lipid-lipid interactions play a role in supporting this function is an unanswered question. Here, we compare the molecular organization of polyunsaturated 1-[2H31]palmitoyl-2-docosahexaenoylphosphatidylethanolamine (PDPE-d31) and, as a control, monounsaturated 1-[2H31]palmitoyl-2-oleoylphosphatidylethanolamine (POPE-d31) mixed with sphingomyelin (SM) and α-tocopherol (α-toc) (2:2:1 mol) by solid-state 2H NMR spectroscopy. In both cases the effect of α-toc appears similar. Spectral moments reveal that the main chain melting transition of POPE-d31 and PDPE-d31 is broadened beyond detection. A spectral component attributed to the formation of inverted hexagonal HII phase in coexistence with lamellar Lα phase by POPE-d31 (20 %) and PDPE-d31 (18 %) is resolved following the addition of α-toc. Order parameters in the remaining Lα phase are increased slightly more for POPE-d31 (7%) than PDPE-d31 (4%). Preferential interaction with polyunsaturated phospholipid is not apparent in these results. The propensity for α-toc to form phase structure with negative curvature that is more tightly packed at the membrane surface, nevertheless, may restrict the contact of free radicals with lipid chains on phosphatidylethanolamine molecules that accumulate polyunsaturated fatty acids.

Luminescence performance of Cerium(III) ions incorporated into organofunctional mesoporous silica

Abstract Series of SBA-15 derived ordered mesoporous silica adsorbents bearing phenylsulfonic, phosphonic groups and their combinations were synthesized by non-grafting approach. Sodium metasilicate was used as precursor for the silica matrix. The materials were characterized using 1H, 31P, 29Si and 13C solid-state NMR spectroscopy, N2-physisorption isotherms, powder XRD, FTIR, TGA, SEM and TEM. It was found that all the samples exhibited typical hexagonal arrangement of mesoporous structure with high surface area. The active organic functions were, at least to some extent, incorporated into the framework of SBA-15, efficiently promoting the uptake of Ce(III) into the produced SBA-15 type matrices. Significant changes in luminescence of the samples were observed with both increasing content of incorporated cation and with change of heteroatoms (O, P, S) in functional groups of silica. The shapes of the peaks at 350–360 nm in the photoluminescence spectra originating from the 4f→5d (2F5/2, 2F7/2) transitions were indicative of the presence of Ce(III) ions in the mesoporous silica matrix with adsorption capacity increasing in the series up to ~2 mmol∙g−1(259.2 mg∙g−1). The Ce-incorporated samples dehydrated in vacuum exhibited decreased photoluminescence with integrated intensities comparable to those of water-containing samples. The high luminescent performances of these luminescent Ce-incorporated mesoporous materials could render attractive potential applications in optical amplification and laser systems, etc.

Preparation, Spectroscopic Characterization and Theoretical Study of a Three-Dimensional Conjugated 70 π-Electron Thiophene 6-mer Radical Cation π-Dimer

A radical cation, generated from an extended π-conjugated thiophene 6-mer composed of four ethynylene-thienylene and two vinylene-thienylene units, was observed to form a stable three-dimensional π-dimer containing 70 π-electrons. The π-dimer prepared in solution was investigated by using magnetic circular dichroism (MCD), ESR spectroscopy, and UV-vis-NIR absorption spectroscopy. Probing the individual NIR absorption bands showed that the MCD signals can be assigned to the pseudo Faraday A term, indicating that the absorption bands are comprised of nearly degenerate electronic transitions. X-ray crystallographic analysis revealed that the π-dimer has a three-dimensional face-to-face and continuous π-conjugated donutlike structure. Analysis of the UV-vis-NIR and ESR spectra of the π-dimer in the solid state confirmed that it possesses the dimer structure. The prediction made by using TD-DFT calculations that the dimer would have a 70 π-electron diatropic nature was confirmed by using solid state 1H NMR spectroscopy.

Elastic Moduli and Collective Dynamics of Phospholipids are Revealed by Solid-State 2H NMR Spectroscopy

Elastic Moduli and Collective Dynamics of Phospholipids are Revealed by Solid-State 2H NMR Spectroscopy

Stiffening of Phosphocholine Membranes by Cholesterol

Cholesterol is a key molecule in controlling membrane fluidity, packing state, and various functions in eukaryotic cell membranes. It also regulates antibiotic drug resistance by augmenting the mechanical properties of its host membrane against structural damage. While, structurally, cholesterol exhibits universal condensing effects on fluid lipid membranes (saturated and unsaturated), its effects on membrane mechanics are presumed to be non-universal. Specifically, cholesterol causes strong stiffening in saturated lipid membranes, yet its mechanical effects on unsaturated lipid membranes remain controversial. Previous studies on di-monounsaturated lipids, such as DOPC, have shown that cholesterol has little effect on the bending rigidity of such membranes, despite clear evidence of a condensing effect. In contrast, neutron spin echo (NSE) spectroscopy shows that cholesterol yields a non-trivial stiffening of DOPC membranes over NSE timescales [1]. Here, we report similar observations using solid-state 2H-NMR spectroscopy. The model-free functional dependence of spin lattice relaxation rates (R1Z) on segmental order parameters (SCD), unambiguously indicates increased membrane bending rigidity with cholesterol [2]. These results are contextualized within the fluctuation-dissipation theorem which connects relaxations from thermal fluctuations in liquid-crystalline membranes to quasi-elastic deformation on mesoscopic length scales. Parallel studies on membranes with different lipid unsaturation (e.g. POPC vs. DOPC) indicate that cholesterol-induced stiffening is dependent on chain unsaturation and is present in all studied membranes. Our dynamical results - as well as structural SANS/SAXS and ESR data - are in excellent agreement with real-space fluctuation analysis from molecular dynamics simulations on cognate DOPC-cholesterol bilayers and with standard theories of membrane mechanics. Our findings have significant biological implications and encourage reassessment of mechanical measurements of cholesterol-containing membranes over length and time scales relevant to biological processes. [1] R. Ashkar et al. Biophys. J. (2019) 116, 328a. [2] T.R. Molugu et al. (2016) Chem. Phys. Lipids 1848, 246.

Determination of n-alkane partitioning within phosphatidylethanolamine Lα/HII phases

Alkanes are known to promote the fluid lamellar (Lα)-to-inverted hexagonal (HII) phase transition of different phospholipids. In this work, we studied the interaction of decane and tetradecane with self-assemblies formed of 1-palmitoyl-2-oleoyl-sn-glycero-phosphoethanolamine (POPE), using sequential 2H and 31P solid-state NMR spectroscopy. This technique allowed calculating the partitioning constant of the alkanes between the Lα and HII phases of POPE. Our results show that both alkanes are preferentially distributed in the HII phase compared to the Lα phase. In the HII phase, both alkanes display a very high conformational disorder, consistent with their location in the intercylinder voids. This preferential partitioning in the HII phase is more pronounced for tetradecane than for decane. This finding is proposed to be associated with a less energetically favored insertion (limited solubility) of tetradecane in the lamellar phase. This proposition is supported by the observation that tetradecane experiences more conformational freedom than its shorter analog in POPE bilayers, suggesting that it is located, on average, closer to the middle of the bilayers. It is also established that the increase in size of the intercylinder voids, by the addition of 1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine (POPC) in the HII cylinders, enhances the partitioning of decane in the HII phase compared to the Lα phase. These findings propose handles to modulate the balance of the relative Lα/HII phase stability.

Polar surface structure of oxide nanocrystals revealed with solid-state NMR spectroscopy

Compared to nanomaterials exposing nonpolar facets, polar-faceted nanocrystals often exhibit unexpected and interesting properties. The electrostatic instability arising from the intrinsic dipole moments of polar facets, however, leads to different surface configurations in many cases, making it challenging to extract detailed structural information and develop structure-property relations. The widely used electron microscopy techniques are limited because the volumes sampled may not be representative, and they provide little chemical bonding information with low contrast of light elements. With ceria nanocubes exposing (100) facets as an example, here we show that the polar surface structure of oxide nanocrystals can be investigated by applying 17O and 1H solid-state NMR spectroscopy and dynamic nuclear polarization, combined with DFT calculations. Both CeO4-termination reconstructions and hydroxyls are present for surface polarity compensation and their concentrations can be quantified. These results open up new possibilities for investigating the structure and properties of oxide nanostructures with polar facets.

Orientation-Dependent Proton Relaxation of Water Molecules Trapped in Solids: Crystallites with Long-Lived Magnetization.

The longitudinal spin-lattice relaxation properties of water molecules trapped in a static powdered polycrystalline sample of barium chlorate monohydrate are investigated by means of solid-state 1H NMR spectroscopy. Different portions of the inhomogeneous Pake pattern that are associated with crystallites at different orientations with respect to the external magnetic field show either a mono- or a biexponential recovery. At high field (9.4 T), the chemical shift anisotropy is the main interaction that is responsible for the inhomogeneity of the relaxation rates. A theoretical description of rapid two-site hopping about the H-O-H bisector in the framework of Liouville space agrees very well with the experimental evidence. Numerical simulations predict a distribution of monoexponential time constants associated with individual single-crystal orientations. Overlapping signals give rise to biexponential recovery. This is confirmed experimentally by 1H NMR spectra of static single crystals.

Hydrogenation Properties of LnAl2 (Ln = La, Eu, Yb), LaGa2, LaSi2 and the Crystal Structure of LaGa2H0.71(2)

Many Zintl phases take up hydrogen and form hydrides. Hydrogen atoms occupy interstitial sites formed by alkali or alkaline earth metals and / or bind covalently to the polyanions. The latter is the case for polyanionic hydrides like SrTr2H2 (Tr = Al, Ga) with slightly puckered honeycomb-like polyanions decorated with hydrogen atoms. This study addresses the hydrogenation behavior of LnTr2, where the lanthanide metals Ln introduce one additional valence electron. Hydrogenation reactions were performed in autoclaves and followed by thermal analysis up to 5.0 MPa hydrogen gas pressure. Products were analyzed by powder X-ray and neutron diffraction, transmission electron microscopy, and NMR spectroscopy. Phases LnAl2 (Ln = La, Eu, Yb) decompose into binary hydrides and aluminium-rich intermetallics upon hydrogenation, while LaGa2 forms a ternary hydride LaGa2H0.71(2). Hydrogen atoms are statistically distributed over two kinds of trigonal-bipyramidal La3Ga2 interstitials with 67% and 4% occupancy, respectively. Ga-H distances (2.4992(2) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. 2H solid-state NMR spectroscopy and theoretical calculations on Density Functional Theory (DFT) level confirm that LaGa2H0.7 is a typical interstitial metallic hydride.

Guests Like Gear Levers: Donor Binding to Coordinatively Unsaturated Metal Sites in MIL-101 Controls the Linker's Rotation.

We present investigation of the effect of electron-donor guests on framework mobility in the metal-organic framework (MOF) MIL-101(Cr) monitored by solid state 2 H NMR spectroscopy. In a guest-free material, the mobile phenylene fragments of the terephthalate (TP) linkers populate two fractions with notably different kinetic parameters for torsional motion. Two fractions of rotational motion are indicative of non-equivalence of TP linker binding to the Cr3 O trimer, the primary building unit of the MIL-101 framework. It is established that the interaction of the guest molecules with coordinatively unsaturated metal sites (CUS) of the MOF dramatically decreases torsional barriers for the linker motions, enhancing the rotation rate. This result is opposite to a more conventional slowing down effect on the linker rotation of the guests not selectively interacting with the adsorption sites inside the framework of the MOFs. The effect of coordination on both the torsional barrier and the rotation rate depends notably on the particular guest interacting with the CUS. The found effects of the guest on the rotational motion represent a basis for developing the strategy for ruling and controlling the linker rotation in MOFs with CUS. It is shown that if water occupies CUS, another guest (tert-butanol, cyclohexanone) fails to competitively coordinate to the site.

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

We report the solid-state structural properties and phase transition behavior of 1,4-dibromo-2,3,5,6-tetramethylbenzene, demonstrating that this material undergoes an order–disorder phase transition below ambient temperature (at ca. 154 K on cooling and ca. 160 K on heating). In both the high-temperature and low-temperature phases, the crystal structure is based on π-stacking of the molecules. In the crystal structure of the high-temperature phase, the bromine occupancy in each substituent site is ca. 1/3 and the methyl group occupancy in each substituent site is ca. 2/3, consistent with statistical orientational disorder of the molecule between six distinct orientations. Natural-abundance solid-state 2H NMR spectroscopy confirms that, at ambient temperature, this disorder is dynamic via rapid molecular reorientation about an axis perpendicular to the aromatic ring. In the low-temperature phase, the bromine and methyl substituents occupy preferred sites within the crystal structure, with the distribution of site occupancies becoming progressively more ordered on decreasing temperature.

Phospholipid Headgroups Govern Emergent Bending Energy of Membranes with Implications for Lipid-Protein Interactions

Activities of integral membrane proteins are strongly affected by lipid molecular properties in the membrane bilayer [1]. Thermal motions in liquid-crystalline membranes modulate nuclear magnetic relaxation giving a connection to membrane mechanical properties through the fluctuation-dissipation theorem. Application of solid-state NMR methods uniquely investigates lipid membranes in terms of both structure and dynamics as they emerge from atomistic-level interactions. Here we employed solid-state 2H NMR spectroscopy [2] and relaxometry [3] to investigate how lipid headgroups influence the properties of 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE-d62) and 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphocholine (DPPC-d62) and their 1:1 mixtures in the liquid-disordered (ld or La) phase. Segmental order parameters (SCD) for DPPE-d62 are greater than DPPC-d62 indicating a smaller area per lipid and greater bilayer thickness. Mixtures of DPPC/DPPE (1:1) with one component deuterated showed nearly identical SCD values, regardless of the lipid species deuterated. Our results suggest SCD is determined by packing of the headgroups and is averaged over the entire system. Additional relaxation studies of the two perdeuterated lipids showed differences in their dynamics. The spin-lattice (R1Z) relaxation rates as a function of SCD2 implied collective mesoscopic dynamics and higher stiffness for DPPE-d62 membranes than for DPPC-d62 at the same temperatures [3]. In the mixtures of DPPE and DPPC the acyl chain dynamics are the same regardless of the associated headgroup and showed intermediate bending elasticities. Variation of both average and dynamic properties with phospholipid headgroup ratio suggests that membrane properties are modulated by the headgroup composition. Solid-state NMR relaxometry thus probes bending energies of biomembranes via mesoscopic dynamics that affect membrane protein function in the natural lipid environment. [1] M.F. Brown (2017) Annu. Rev. Biophys. 46, 379. [2] T.R. Molugu et al. (2017) Chem.Rev. 117, 12087. [3] T.R. Molugu et al. (2016) Chem.Phys.Lipids 199, 39.

Solid-State NMR Approaches to Study Protein Structure and Protein-Lipid Interactions.

Solid-state NMR spectroscopy has been developed for the investigation of membrane-associated polypeptides and remains one of the few techniques to reveal high-resolution structural information in liquid-disordered phospholipid bilayers. In particular, oriented samples have been used to investigate the structure, dynamics and topology of membrane polypeptides. Much of the previous solid-state NMR work has been developed and performed on peptides but the technique is constantly expanding towards larger membrane proteins. Here, a number of protocols are presented describing among other the reconstitution of membrane proteins into oriented membranes, monitoring membrane alignment by 31P solid-state NMR spectroscopy, investigations of the protein by one- and two-dimensional 15N solid-state NMR and measurements of the lipid order parameters using 2H solid-state NMR spectroscopy. Using such methods solid-state NMR spectroscopy has revealed a detailed picture of the ensemble of both lipids and proteins and their mutual interdependence in the bilayer environment.

Lipid-Mediated Interactions between the Antimicrobial Peptides Magainin 2 and PGLa in Bilayers

A synergistic enhancement of activities has been described for the amphipathic cationic antimicrobial peptides magainin 2 and PGLa when tested in antimicrobial assays or in biophysical experiments using model membranes. In the presence of magainin 2, PGLa changes from an in-planar alignment parallel to the membrane surface to a more transmembrane orientation when investigated in membranes made from fully saturated PC or PC/PG, but not when one of the fatty acyl chains is unsaturated. Such lipid-mediated changes in the membrane topology of polypeptide domains could provide an interesting mechanism for the regulation of membrane proteins. Here we investigated the PGLa topology in a wide variety of membranes made of saturated or unsaturated PE, PC, and/or PG using 15N solid-state NMR spectroscopy. In contrast to predictions made by previous models the data show that membrane curvature has only a minor effect on PGLa realignment. Furthermore, using 2H solid-state NMR spectroscopy of deuterated phospholipid fatty acyl chains the order parameters of the lipids were investigated in the presence of PGLa, magainin, or equimolar peptide mixtures. Both peptides cause a pronounced decrease in the order parameters when oriented parallel to the membrane surface, an effect that reverts when PGLa flips into transmembrane alignments. Taken together, these data are suggestive that the magainin-induced disordering of fatty acyl chains provides an important driving force for PGLa realignment.

Probing local structure of paramagnetic Ni-Al layered double hydroxides with solid-state 2H NMR spectroscopy

2H MAS NMR spectroscopy was applied to investigate the local structure of deuterated paramagnetic Ni2+-containing layered double hydroxides (LDHs) for the first time. Due to significantly smaller electronic dipole interaction, 2H NMR spectra of NiAl-LDHs show much better resolution than 1H NMR spectra, and different hydrogen species, including Ni3OD, Ni2AlOD and interlayer water, can be resolved in 2H NMR spectra. Quantitative analysis of the NMR spectra of LDHs with different Al percentages confirms the ordering of Al3+ ions in the hydroxide sheets (Al-O-Al avoidance). 2H MAS NMR spectroscopy gives new insight into different hydrogen species in paramagnetic NiAl-LDH and this approach can be extended to study the detailed structural information and properties of other paramagnetic LDHs.