Search results for "Solid-state nuclear magnetic resonance"
showing 10 items of 61 documents
Crystallization, spectral, crystallographical, and thermoanalytical studies of succinobucol polymorphism.
2011
Four different polymorphs, A, C, D, and E, of succinobucol were isolated and characterized by means of solid-state nuclear magnetic resonance spectroscopy, single crystal and powder X-ray diffraction, differential scanning calorimetry, thermogravimetry, and attenuated total reflection–infrared spectroscopy. From a number of experiments, the same polymorphs (C, D, and E) and an equilibrium phase mixture B consisting of polymorphs C and D were repeatedly gained using different solvents or their mixtures. Although polymorph A was obtained directly from recrystallization only on few occasions, polymorphs C, D, and E proved to be metastable kinetic polymorphs, which slowly transform to a thermod…
Solid-state NMR and computational investigation of solvent molecule arrangement and dynamics in isostructural solvates of droperidol.
2015
(13)C, (15)N and (2)H solid-state NMR spectroscopy have been used to rationalize arrangement and dynamics of solvent molecules in a set of isostructural solvates of droperidol. The solvent molecules are determined to be dynamically disordered in the methanol and ethanol solvates, while they are ordered in the acetonitrile and nitromethane solvates. (2)H NMR spectra of deuterium-labelled samples allowed the characterization of the solvent molecule dynamics in the alcohol solvates and the non-stoichiometric hydrate. The likely motion of the alcohol molecules is rapid libration within a site, plus occasional exchange into an equivalent site related by the inversion symmetry, while the water mo…
Unraveling the packing pattern leading to gelation using SS NMR and X-ray diffraction: direct observation of the evolution of self-assembled fibers
2010
A detailed understanding of the mode of packing patterns that leads to the gelation of low molecular mass gelators derived from bile acid esters was carried out using solid state NMR along with complementary techniques such as powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and polarizing optical microscopy (POM). Solid state 13C{1H} cross polarization (CP) magic angle spinning (MAS) NMR of the low molecular mass gel in its native state was recorded for the first time. A close resemblance in the packing patterns of the gel, xerogel and bulk solid states was revealed upon comparing their 13C{1H}CPMAS NMR spectral pattern. A doublet r…
NMR Spectra of Anilines
2009
1 Introduction 2 Ring and N-Substituted Anilines 3 Multinuclear NMR Studies of p-F-Aniline Derivatives 4 Dynamic NMR of Aniline Derivatives 5 Anilines with Other (Fused) Aromatic Rings 6 NMR Relaxation Studies of Aniline Derivatives 7 Solid State NMR Studies 8 Theoretical Calculations of Aniline NMR Parameters Keywords: aniline NMR spectra; aniline (aminobenzene, phenylamine); ring and N-substituted anilines; dual-substituent-parameter (DSP) analysis; cyclic amine structures; dynamic NMR of aniline derivatives; H NMR spectroscopy as measure of donor strengths; aniline derivative NMR relaxation studies
Solid-state NMR investigation on the interactions between a synthetic montmorillonite and two homopolypeptides.
2006
Abstract Interactions of two homopolypeptides (polylysine and polyglutamic acid) with a synthetic montmorillonite were studied by 1H MAS, 1H–27Al HETCOR and 1H–13C CP-MAS NMR experiments. 1H–27Al HETCOR with 1H spin-diffusion NMR appears to be a powerful probe for the identification of the polypeptide fragments, which interact with the montmorillonite interlayer surfaces. In particular, selective interactions were observed between the polypeptide side-chains and the montmorillonite octahedral aluminum atoms. 1H–13C CP-MAS NMR experiments were used to assess the dynamics of the two polypeptides through the measurement of the t1/2 characteristic time of selected carbons. Results indicate that…
Nuclear magnetic resonance at millitesla fields using a zero-field spectrometer
2016
We describe new analytical capabilities for nuclear magnetic resonance (NMR) experiments in which signal detection is performed with chemical resolution (via spin-spin J couplings) in the zero to ultra-low magnetic field region, below 1μT. Using magnetic fields in the 100μT to 1mT range, we demonstrate the implementation of conventional NMR pulse sequences with spin-species selectivity.
Pre- and post-modification of mixed cyclodextrin-calixarene co-polymers: A route towards tunability
2017
Various pre-modified and post-modified cyclodextrin-calixarene hyper-reticulated co-polymers were synthesized, fully characterized by different techniques (FT-IR, 13C{1H} CP-MAS and LGFS solid-state NMR, thermogravimetry, porosimetry), and tested to assess their absorption abilities as nanosponges. The construction of the polymer network was accomplished exploiting the well-known CuAAC reaction between two different heptakis-6-azido-β-cyclodextrins and two different propargyloxy-calix[4]arenes. Post-modification was aimed to achieve the presence of ionizable (acidic or basic) groups on the polymer framework. Sequestration tests towards two model pollutant molecules surprisingly showed that …
Influence of Dynamics on The Analysis of Solid-State NMR Data From Membrane-bound Peptides
2009
By isotope labeling of membrane-bound peptides, typically with 2H, 19F, or 15N, solid-state NMR experiments can yield data from which the orientation of peptides in a native membrane environment can be determined. Such an orientation is defined by a tilt angle and an azimuthal rotation angle.Here we show that to obtain correct values of the orientation angles, it is important to include dynamics in the analysis of the NMR data. Nevertheless the effects of dynamics are different depending on the type of isotope labeling and NMR experiment considered.To analyze the influence of dynamics in detail, we generated virtual NMR observables using a model peptide undergoing explicit Gaussian fluctuat…
Secondary interactions as driving force in heterocomplex formation of 2,7-disubstituted-1,8-naphthyridines: Quantum chemical, NMR and mass spectral i…
2009
Abstract Tautomerism and dimerization of 2,7-disubstituted-1,8-naphtyridines has been studied theoretically by quantum chemical methods and experimentally by liquid and solid state NMR and ESI-TOF mass spectral techniques. The heterocomplex formation has been proven in solution by variable temperature 1H NMR and in solid state by 13C CPMAS NMR spectra of a grinded mixture of two congeners. Secondary interactions have been proposed as driving forces in the heterocomplex formation. The energy differences between homo- and heterocomplexes were calculated with recently developed DFT + D methods. The energy data obtained by the quantum chemical methods are in agreement with the concept of second…