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77Se‐NMR is used to characterise several chalcogen bonded complexes of derivatives of the organoselenium drug ebselen, exploring a range of electron demand. NMR titration experiments support the intuitive understanding that chalcogen bond donors bearing more electron withdrawing substituents give rise stronger chalcogen bonds. The chemical shift of the selenium nucleus is also shown to move upfield as it participates in a chalcogen bond. Solid‐state NMR is used to explore chalcogen bonding in co‐crystals. Due to the lack of molecular reorientation on the NMR timescale in the solid state, the shape of the chemical shift tensor can be determined using this technique. A range of co‐crystals are shown to have extremely large chemical shift anisotropy, which suggests a strongly anisotropic electron density distribution around the selenium atom. A single crystal NMR experiment was conducted using one of the co‐crystals, affording the absolute orientation of the chemical shift tensor within the crystal. This showed that the selenium nucleus is strongly shielded in the direction of the chalcogen bond (due to the approach of the lone pair of the Lewis base), and strongly deshielded in the perpendicular direction. The orientation of the deshielded axis is consistent with the presence of a second σ‐hole which is not participating in a chalcogen bond, showing the profound effect of electron density anisotropy on the chemical shift. [ABSTRACT FROM AUTHOR]

Cerussite, PbCO 3 , like all members of the aragonite group, shows a tendency to form twins, due to high pseudo-symmetry within the crystal structure. We here demonstrate that the twin law of a cerussite contact twin may be established using only 207 Pb-NMR spectroscopy. This is achieved by a global fit of several sets of orientation-dependent spectra acquired from the twin specimen, allowing to determine the relative orientation of the twin domains. Also, the full 207 Pb chemical shift tensor in cerussite at room temperature is determined from these data, with the eigenvalues being δ 11 = (- 2315 ± 1) ppm, δ 22 = (- 2492 ± 3) ppm, and δ 33 = (- 3071 ± 3) ppm. [ABSTRACT FROM AUTHOR]

We report solid‐state 87Rb NMR spectra from two Rb‐ionophore complexes obtained with fast magic‐angle spinning (MAS) (up to 60 kHz) at 21.1 T. These Rb‐ionophore complexes containing macrocycles such as benzo‐15‐crown‐5 and cryptand [2.2.2] are typical of organic Rb salts that exhibit very large 87Rb quadrupole coupling constants (close to 20 MHz). We have also obtained static 87Rb NMR spectra for these two compounds and determined both 87Rb quadrupole coupling and chemical shift tensors. The experimental 87Rb NMR tensor parameters are compared with those obtained by quantum chemical computations. Our results demonstrate that the combination of fast MAS (60 kHz or higher) and a high magnetic field (21.1 T or higher) is sufficient to produce high‐quality solid‐state 87Rb NMR spectra for organic Rb solids at the natural abundance level. We anticipate that, with additional 87Rb isotope enrichment (up to 99%), the sensitivity of solid‐state 87Rb NMR will be 400 times higher than 39K NMR, which makes the former an attractive surrogate probe for studying K+ ion binding in biological systems. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are a class of important porous materials with many current and potential applications. Their applications almost always involve the interaction between host framework and guest species. Therefore, understanding of host–guest interaction in MOF systems is fundamentally important. Solid‐state NMR spectroscopy is an excellent technique for investigating host–guest interaction as it provides information complementary to that obtained from X‐ray diffraction. In this work, using MOF α‐Mg3(HCOO)6 as an example, we demonstrated that 13C chemical shift tensor of organic linker can be utilized to probe the host–guest interaction in MOFs. Obtaining 13C chemical shift tensor components (δ11, δ22, and δ33, where δ11 ≥ δ22 ≥ δ33) in this MOF is particularly challenging as there are six coordinatively equivalent but crystallographically non‐equivalent carbons in the unit cell with very similar local coordination environment. Two‐dimensional magic‐angle‐turning experiments were employed to measure the 13C chemical shift tensors of each individual crystallographically non‐equivalent carbon in three microporous α‐Mg3(HCOO)6 samples with different guest species. The results indicate that the δ22 component (with its direction approximately being co‐planar with the formate anion and perpendicular to the C−H bond) is more sensitive to the adsorbate molecules inside the MOF channel due to the weak C−H···O hydrogen bonding or the ring current effect of benzene. The 13C isotropic chemical shift, on the other hand, seems much less sensitive to the subtle changes in the local environment around formate linker induced by adsorption. The approach described in this study may be used in future studies on host–guest interaction within MOFs. [ABSTRACT FROM AUTHOR]

The design and implementation of a software package for the analysis of single-crystal NMR data is presented. The SCFit software can treat spectra arising from various interactions: (i) chemical shift tensor only; (ii) chemical shift tensor and quadrupolar coupling tensor; (iii) dipolar and indirect nuclear spin-spin coupling tensors; (iv) all four interactions. The software is demonstrated on recently reported 17O and 31P single-crystal NMR data for triphenylphosphine oxide and for two of its halogen-bonded cocrystals. The 17O single-crystal NMR data represent a case where all four above-mentioned interactions simultaneously affect the spectra. SCFit can fit the chemical shift and quadrupolar coupling in two ways: (i) through an unconstrained fitting process where all tensor parameters are freely optimized or (ii) through a constrained fitting process where the principal components of the tensors may be fixed to values known previously with high precision via the analysis of powder samples. The second strategy is explored in an effort to reduce the number of unknowns in the fitting process; an improvement in the precision of the resulting tensor orientations is noted in some cases. Image 1 • SCFit software for analyzing single-crystal NMR data is described. • Chemical shift, quadrupolar, and spin-spin coupling interactions are treated. • The utility of fixing tensor magnitudes to known values is explored. [ABSTRACT FROM AUTHOR]

In the present work, the non-bonding interaction of the new drug Alectinib and the CNT(6,6-6) nanotube has been studied at the B3LYP/6-31G* level of theory. Results have shown that the electronic properties, chemical shift tensors, and natural charges are sensitive to the adsorption on the CNT(6,6-6) nanotube. Furthermore, we studied the electronic spectra of the Alectinib and the complex CNT(6,6-6)/Alectinib by time dependent DFT (TD-DFT) method for investigation of the maximum wavelength value of the Alectinib before and after the non-bonded interaction with the CNT(6,6-6) nanotube. It was found that the adsorption of the compound Alectinib over the CNT(6,6-6) changed the value λmax as bathochromic shift. [ABSTRACT FROM AUTHOR]

Chemical shift tensors (CSTs) are an exquisite probe of local geometric and electronic structure. 15 N CST are very sensitive to hydrogen bonding, yet they have been reported for very few proteins to date. Here we present experimental results and statistical analysis of backbone amide 15 N CSTs for 100 residues of four proteins, two E. coli thioredoxin reassemblies (1-73-(U- 13 C, 15 N)/74-108-(U- 15 N) and 1-73-(U- 15 N)/74-108-(U- 13 C, 15 N)), dynein light chain 8 LC8, and CAP-Gly domain of the mammalian dynactin. The 15 N CSTs were measured by a symmetry-based CSA recoupling method, ROCSA. Our results show that the principal component δ 11 is very sensitive to the presence of hydrogen bonding interactions due to its unique orientation in the molecular frame. The downfield chemical shift change of backbone amide nitrogen nuclei with increasing hydrogen bond strength is manifested in the negative correlation of the principal components with hydrogen bond distance for both α-helical and β-sheet secondary structure elements. Our findings highlight the potential for the use of 15 N CSTs in protein structure refinement. [ABSTRACT FROM AUTHOR]

In the present work the adsorption properties of the molecule Resveratrol (RSV) ( trans -3,5,4′-Trihydroxystilbene) on CNT(8,0-10) nanotube was investigated by Density Functional Theory (DFT) in the gaseous phase for the first time. The non-bonded interaction effects of compounds RSV and CNT(8,0-10) nanotube on the electronic properties, chemical shift tensors and natural charge were determined and discussed. The electronic spectra of the RSV and the complex CNT(8,0-10)/RSV in the gaseous phase were calculated by Time Dependent Density Functional Theory (TD-DFT) for investigation of the maximum wavelength value of the RSV before and after the non-bonded interaction with the CNT(8,0-10) nanotube and molecular orbitals involved in the formation of absorption spectrum of the complex RSV at maximum wavelength. [ABSTRACT FROM AUTHOR]

In the present work, Density Functional Theory (DFT) was first time employed to investigate the interaction between new drug (6aR,10aR)-6,6,9-trimethyl-3-pentyl-6a,7,8,10a-tetrahydrobenzo[c]chromen-1-ol (Syndros) and the CNT(6,6-6) Nanotube in the gaseous phase. The interaction effects of compounds Syndros and CNT (6,6-6) nanotube on the electronic properties, chemical shift tensors and natural charge was also determined and discussed. The electronic spectra of the Syndros and the complex CNT(6,6-6)/Syndros in the gas phase were calculated by Time Dependent Density Functional Theory (TD-DFT) for the formation of adsorption effect on maximum wavelength of the Syndros. Nucleus-Independent Chemical Shifts (NICS) calculations have also been carried out for the compound Syndors and the complex CNT(6,6-6)/Syndros and the aromaticity of the compound Syndors before and after interaction with the CNT(6,6-6) Nanotube was investigated. [ABSTRACT FROM AUTHOR]

In this present work, first time interaction between new synthesized derivative of the 4-(( E )-((4-(( E )-phenyldiazenyl)phenyl)imino)methyl)benzoic acid (E-PABA) and the BN(6,6-7) Nanotube for medical applications were studied. The geometries of the compounds E-PABA, the BN(6,6-7) Nanotube and the Complex BN(6,6-7)/E-PABA were optimized by Density Functional Theory (DFT) in the gas phase. The adsorption effect of the compound E-PABA on the electronic properties, chemical shift tensors and natural charge of the BN(6,6-7) Nanotube was investigated and discussed. The electronic spectra of the E-PABA and the Complex BN(6,6-7)/E-PABA in the gas phase carried out by Time Dependent Density Functional Theory (TD-DFT) for the foundation adsorption effect on maximum wavelength of the E-PABA. [ABSTRACT FROM AUTHOR]

An improved implementation of single-crystal magic-angle-spinning (MAS) NMR is presented which gives access to chemical shift tensors both in orientation (relative to the crystal axis system) and principal axis values. For mounting arbitrary crystals inside ordinary MAS rotors, a mounting tool is described which allows to relate the crystal orientation determined by diffraction techniques to the rotor coordinate system. The crystal is finally mounted into a MAS rotor equipped with a special insert which allows a defined reorientation of the single-crystal by 90°. The approach is based on the idea that the dispersive spectra, which are obtained when applying read-pulses at specific rotor-phases, not only yield the size of the eigenvalues but also encode the orientation of the different chemical shift (rank-2) tensors. For this purpose two 2D-data sets with orthogonal crystal orientation are fitted simultaneously. The presented analysis for chemical shift tensors is supported by an analytical formula which allows fast calculation of phase and amplitude of individual spinning side-bands and by a protocol which solves the problem of finding the correct reference phase of the spectrum. Different rotor-synchronized pulse-sequences are introduced for the same reason. Experiments are performed on L -alanine and O-phosphorylethanolamine and the observed errors are analyzed in detail. The experimental data are opposed to DFT-computed chemical shift tensors which have been obtained by the extended embedded ion method. [ABSTRACT FROM AUTHOR]

We report synthesis and solid-state 17 O NMR characterization of four site-specifically 17 O-labeled 2-acylbenzoic acids (2-RC(O)C 6 H 4 COOH) where R=H and CH 3 ): 2-[3- 17 O]formylbenzoic acid, 2-[1,2- 17 O 2 ]formylbenzoic acid, 2-[3- 17 O]acetylbenzoic acid, and 2-[1,2,3- 17 O 3 ]acetylbenzoic acid. In the solid state, both 2-formyl- and 2-acetyl-benzoic acids exist as the cyclic phthalide form each containing a five-membered lactone ring and a cyclic hemiacetal/hemiketal group. Static and magic-angle-spinning 17 O NMR spectra were recorded at 14.1 and 21.1 T for these compounds, from which the 17 O chemical shift and nuclear quadrupolar coupling tensors were determined for each oxygen site. These results represent the first time that 17 O NMR tensors are fully characterized for lactone, cyclic hemiacetal, and cyclic hemiketal functional groups. We also report solid-state 17 O NMR data for the cyclic hemiketal group an anticoagulant drug, warfarin. Experimental 17 O NMR tensors in these compounds were compared with computational results obtained with a periodic DFT code BAND. [ABSTRACT FROM AUTHOR]

Single crystals of the compound [ { S c ( H 2 O) 5 (μ - O H) } 2 ]Cl 4 ⋅ 2H 2 O were studied by 45Sc-NMR, with the effect of the quadrupolar coupling interaction on the spectra of the spin-7/2 nucleus analysed in the hierarchical framework of perturbation theory. Orientation-dependent spectra acquired at B 0 = 17.6 T showed strong second-order effects due to the comparatively large coupling constant of χ = |14.613 ± 0.006| MHz, with an associated asymmetry parameter of η Q = 0.540 9 ± 0.000 4. By analysing the splittings of the ±3/2 satellites, which in good approximation are subjected to first-order effects only, the full quadrupolar coupling tensor could be determined. The second-order effects caused by this tensor were calculated according to theoretical predictions for all orientations, and subtracted from both the centres of gravity of the satellites, and the central transitions. This allowed extraction of the full chemical shift tensor, with the eigenvalues being δ 11 = (5.6 ± 0.9) ppm, δ 22 = (12.4 ± 0.9) ppm, and δ 33 = (38.5 ± 0.9) ppm. In spectra acquired at a lower magnetic field of B 0 = 9.4 T, third-order effects could be detected, and similarly quantified using analytical expressions. [Display omitted] • Single-crystal NMR of 45Sc (I = 7/2) in [{Sc(H 2 O) 5 (μ-OH)} 2 ]Cl 4 . 2H 2 O. • Spectra analysed in the hierarchical framework of perturbation theory. • Compact new notation for quadrupolar effects of second and third order. • Full tensor of quadrupolar interaction and chemical shift determined. [ABSTRACT FROM AUTHOR]

Abstract: Chemical shift tensors for the carboxyl and methyl carbons of l-alanine crystals were determined using a magnetically oriented microcrystal array (MOMA) prepared from a microcrystalline powder sample of l-alanine. A MOMA is a single-crystal-like composite in which microcrystals are aligned three-dimensionally in a matrix resin. The single-crystal rotation method was applied to the MOMA to determine the principal values and axes of the chemical shift tensors. The result showed good agreement with the literature data for the single crystal of l-alanine. This demonstrates that the present technique is a powerful tool for determining the chemical shift tensor of a crystal from a microcrystal powder sample. [Copyright &y& Elsevier]

The results of a 35/37Cl solid-state nuclear magnetic resonance (SSNMR) study of the 1-butyl-3-methylimidazolium chloride complex of meso-octamethylcalix[4]pyrrole ( 1) are reported. Line shapes obtained from magic-angle-spinning and stationary powder samples collected at 9.4 and 21.1 T are analyzed to provide the 35/37Cl quadrupolar tensor and chemical shift (CS) tensor and their relative orientation. The relatively high symmetry of the chloride ion coordination environment is manifested in the small value of the quadrupole coupling constant, CQ(35Cl) = 1.0 MHz. The isotropic chemical shift of 120 ppm (with respect to NaCl(s)) is at the upper edge of the typical range seen for organic hydrochlorides. Consideration of chemical shift anisotropy (span, Ω = 50 ppm) and non-coincidence of the quadrupolar and CS tensors were essential to properly simulate the experimental spectra. The utility of gauge-including projector-augmented wave density functional theory (GIPAW-DFT) calculations of chlorine quadrupolar and CS tensors in organic chlorides was explored by validation against available benchmark experimental data for solid amino acid hydrochlorides. The calculations are shown to systematically overestimate the value of the 35Cl quadrupole coupling constant. Additional calculations on various hydrated and solvated models of 1 are consistent with a structure in which solvent and water of hydration are absent. [ABSTRACT FROM AUTHOR]

Abstract: 5-Fluoro-dl-tryptophan (5F-Trp) is a very sensitive probe used to investigate orientation and dynamics of biomacromolecules at the in situ level. In order to establish a 19F NMR strategy, the crystal structure and 19F chemical shielding tensor of 5F-Trp are reported. A novel approach was developed to use F–F homonuclear dipole–dipole coupling information to analyze single-crystal NMR data without determining crystal orientations. The measured values for the principal components of the shielding tensor are σ 11 =0.9, σ 22 =−63.3, and σ 33 =−82.9ppm relative to TFA in D2O. The principal axes of the shielding tensors coincide with the indole ring symmetry, which makes it a straightforward and powerful tool to monitor protein alignment in oriented environments. Hartree–Fock (HF) and density functional theory (DFT) calculations of the chemical shielding tensors are also reported. [Copyright &y& Elsevier]

Abstract: Bayesian statistics and information theory are used to analyze the reliability of extracting chemical shift parameters from spinning sideband patterns of spin 1/2 systems. Efficient code has been written to calculate the two-dimensional posterior probability as a function of the chemical shift anisotropy, δ, and the asymmetry parameter, η, given the sideband intensities and the signal-to-noise ratio. This method has the advantage of assuming only that the noise in the sideband intensities is distributed as a Gaussian. It assumes nothing about the distribution of the values of parameters δ and η, which are shown in some cases to be highly non-Gaussian. The utility of Bayesian analysis is demonstrated on 1D slow-spinning MAS spectra and on sideband patterns extracted from 2D PASS spectra. Previous investigations have shown that there is an optimal range of spinning frequencies for determining δ. In this study, information theory is used to determine the signal-to-noise ratio dependence of the entropy in δ, η, and total entropy in spinning sideband spectra. The entropy is a measure of the information content of a probability distribution. When the entropy is zero, there is perfect information on a system, while if it is infinite, there is no information on the system. It is found that for all values of η and for signal-to-noise ratios in the range 50–1000, an entropy minimum in ν δ /ν r occurs for values 1.5⩽ ν δ /ν r ⩽3. In the same range of signal-to-noise ratios, the entropy in η is a monotonically decreasing function of ν δ /ν r . The global information content of a spinning sideband pattern (i.e., the total entropy) is dependent on the signal-to-noise ratio and has an optimal value at ν δ /ν r ≈2 at a signal-to-noise ratio of 50 and increasing to ≈2.5 for signal-to-noise ratios of 1000. Finally, the increase of information in a sideband pattern as a function of the number of sidebands used in the analysis is examined. Most of the information about δ and η is contained in the five central sidebands; i.e., sidebands −2 to 2. [Copyright &y& Elsevier]

Abstract: A new interpretation of 13C chemical shift tensors of amino acid carboxyl groups is presented. It is based on NMR results for 50 crystalline complexes of β-alanine, betaine, glycine and sarcosine with different inorganic and organic acids (XH), X-ray and vibrational data on the same systems and GIAO calculations for model complexes: (CH3COO–HX)−. Sensitivity of the chemical shift tensors on the amino acid electronic structure, crystal lattice, kind and strength of the hydrogen bonds is characterised in this way. Four categories of the complexes and hydrogen bonds are considered: (i) MO – the molecular complexes with the bonding proton not transferred to the amino acid carboxylate group, COO−⋯H–X; (ii) IP – the hydrogen bonded ion pairs with the bonding proton localised at the amino acid oxygen atom, COO–H⋯X−; (iii) BHB – the homoconjugated amino acid complexes with the bonding proton in the central region of short hydrogen bond, (COO–H–OOC)−; (iv) low-barrier hydrogen bonds with disordered proton position. Properties of the last category bonds are discussed by means of Mulliken theory of CT complexes. [Copyright &y& Elsevier]

Cobalt-59 and nitrogen-15 NMR spectra of the nitritopentamminecobalt(III) chloride, [(NH3)5Co-ONO]Cl2, and nitropentamminecobalt(III) chloride, [(NH3)5Co-NO2]Cl2, isomers in the solid state have been obtained at several applied magnetic field strengths. The 59Co NMR line shapes indicate that both the cobalt nuclear quadrupolar coupling constant (CQ) and the span of the chemical shift tensor (Ω) decrease when the complex isomerizes from [(NH3)5Co-ONO]2+ to [(NH3)5Co-NO2]2+; CQ decreases from 23 to 10.3 MHz and Ω changes from 1650 to 260 ppm. The 15N NMR line shapes also show a significant change in the nitrogen magnetic shielding tensor upon isomerization, with Ω decreasing from 710 to 547 ppm; also, an indirect spin-spin coupling, 1J(59Co,15N) = 63 Hz, is observed in the 15N NMR spectra of the nitro isomer. The NMR parameters are rationalized based on differences in the molecular structure of the two isomers. NMR spectra have also been recorded as the isomerization progresses with time and demonstrate the practicality of the technique for the study of solid-state isomerizations. [ABSTRACT FROM AUTHOR]

The 29Si-NMR chemical shift tensors of 21 simple singlet silylenes, R2Si:, are studied at the GIAO/MP2/6-311+G(2df,p)//B3LYP/6-311G(d,p) level of theory. The NMR chemical shielding tensor for all silylenes is predicted to be highly anisotropic, with a very large paramagnetic eigenvalue δ11 in the plane of the central R2Si unit and perpendicular to its C2 axis. Very large substituent effects on δ29Si are found, i.e., while for H2Si: δ29Si=772 is predicted, the divalent silicon in F2Si is strongly shielded (δ29Si=−9.3). On the other hand for (H3Si)2Si: δ29Si=1223 is computed. This exceptional substituent effects are a direct consequence of large changes of the dominant eigenvalue δ11. The theoretical analysis reveals, that δ11 in silylenes is determined by the energy difference between its lowest excited singlet state, S1, and the S0 ground state. Therefore, a direct relation between the experimentally easy accessible λmax of silylenes and the isotropic 29Si-NMR chemical shift exists. This correlation can be used to facilitate the NMR characterization of highly substituted silylenes. [Copyright &y& Elsevier]

Solid-state 17O NMR spectra were obtained at 4.70, 11.75 and 19.60 T for potassium hydrogen [17O4]dibenzoate (PHB) under both magic-angle spinning and stationary conditions. Spectral analyses yielded both the magnitude and orientation of the 17O chemical shift (CS) tensor and the electric field gradient (EFG) tensor for each of the two chemically distinct oxygen sites in PHB. For the oxygen site that is not involved in hydrogen bonding, the experimental 17O NMR tensors are: δiso=287±2 ppm, δ11=470±5 ppm, δ22=380±5 ppm, δ33=10±5 ppm, CQ=8.30±0.02 MHz, ηQ=0.23±0.05, α=0±5°, β=90±5°, and γ=30±5°. For the oxygen site in the short O⋯H⋯O hydrogen bond, the experimental 17O NMR tensors are: δiso=213±2 ppm, δ11=370±5 ppm, δ22=190±5 ppm, δ33=80±5 ppm, CQ=5.90±0.02 MHz, ηQ=0.55±0.05, α=5±5°, β=90±5°, and γ=90±5°. Extensive quantum mechanical calculations at both restricted Hartree–Fock and density functional theory levels were performed to investigate the effects of an effectively symmetrical O⋯H⋯O hydrogen bond on 17O CS and EFG tensors. [Copyright &y& Elsevier]

Cobalt-59 NMR experiments have been carried out on single-crystal and polycrystalline (powder) samples of (±)-tris(ethylenediamine)cobalt(III) chloride trihydrate, (±)-[Co(en)3]Cl3·3H2O, and of its dehydrate. In addition, the X-ray crystal structure of the dehydrated sample has been determined. X-ray diffraction measurements confirm a long-held assumption that dehydration has only minor effects on the structure of the [Co(en)3]3+ cation. Nevertheless, these small differences have a detectable effect on the 59Co nuclear magnetic resonance properties of these compounds; in particular, the nuclear quadrupole coupling constant, CQ. Straightforward identification of the c-axis for large single crystals of (±)-[Co(en)3]Cl3·3H2O and of its dehydrate allowed us to obtain single-crystal 59Co NMR data by orienting the crystals in an MAS rotor. Data collected on single crystals and polycrystalline samples indicate that CQ=−3.05±0.05 and −2.80±0.05 MHz for the hydrated and dehydrated samples, respectively; the signs have been assigned on the basis of a point charge model. The chemical shift tensor principal components were also determined: for the hydrated sample, δ⊥=7281±2 ppm, δ||=7004±4 ppm and δiso=7189 ppm; for the dehydrated sample, δ⊥=7288±2 ppm, δ||=7008±4 ppm and δiso=7195 ppm. The electric field gradient and chemical shift tensors are axially symmetric, as required by crystal symmetry. [Copyright &y& Elsevier]

Silver methanesulfonate, AgSO3CH3, is a photo-stable, commercially available compound which is a superior 109Ag standard for setting up CP/MAS experiments. The 109Ag CP/MAS spectrum at moderate sample spinning speeds easily yields a single, relatively narrow peak with a single transient. The 109Ag chemical shift of solid AgSO3CH3 is 87.2 ppm with respect to a 9 M aqueous solution of AgNO3. The static spectrum yields chemical shift tensor components δ11=191 ppm, δ22=63 ppm and δ33=8 ppm. Therefore the span, Ω, is 183 ppm and the skew, κ, is −0.39. These values are in accord with the known crystal structure. [Copyright &y& Elsevier]

Both the chemical shift and quadrupole coupling tensors for 14 N and 27 Al in the wurtzite structure of aluminum nitride have been determined to high precision by single-crystal NMR spectroscopy. A homoepitaxially grown AlN single crystal with known morphology was used, which allowed for optical alignment of the crystal on the goniometer axis. From the analysis of the rotation patterns of 14 N ( I = 1 ) and 27 Al ( I = 5 / 2 ), the quadrupolar coupling constants were determined to χ (14 N) = (8.19 ± 0.02) kHz, and χ (27 Al) = (1.914 ± 0.001) MHz. The chemical shift parameters obtained from the data fit were δ i s o = − (292.6 ± 0.6) ppm and δ Δ = − (1.9 ± 1.1) ppm for 14 N, and (after correcting for the second-order quadrupolar shift) δ i s o = (113.6 ± 0.3) ppm and δ Δ = (12.7 ± 0.6) ppm for 27 Al. DFT calculations of the NMR parameters for non-optimized crystal geometries of AlN generally did not match the experimental values, whereas optimized geometries came close for 27 Al with χ ¯ calc = (1.791 ± 0.003) MHz, but not for 14 N with χ ¯ calc = − (19.5 ± 3.3) kHz. [ABSTRACT FROM AUTHOR]