Solid State NMR for Nonexperts: An Overview of Simple but General Practical Methods (original) (raw)
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High resolution 31P solid state NMR in phosphorus-transition metal compounds
Materials Chemistry and Physics, 1991
The use of a high resolution solid state 31P NMR technique to investigate the coordination of phopshorus ligands bound to transition metal atoms is reviewed using examples which include information on molecular structure and crystallographic sites in organometallic solids, and characterization of supported transition metal complexes on surfaces. Moreover 31P CPMAS (cross polarization magic angle spinning) experiments can afford a wealth of information such as chemical shift anisotropy, isotropic coupling constants with quadrupolar nuclei and quadrupole coupling constants that are often obscured in solution state due to the rapid isotropic motion of the molecules.
Physical chemistry chemical physics : PCCP, 2017
A benchmark for structural interpretation of the P NMR shift and the J NMR spin-spin coupling in the phosphate group was obtained by means of theoretical calculations and NMR measurements in diethylphosphate (DEP) and 5,5-dimethyl-2-hydroxy-1,3,2-dioxaphosphinane 2-oxide (cDEP). The NMR parameters were calculated employing the B3LYP, BP86, BPW91, M06-2X, PBE0, KT2, KT3, MP2, and HF methods, and the 6-31+G(d), Iglo-n (n = II, III), cc-pVnZ (n = D, T, Q, 5), aug-cc-pVnZ (n = D, T and Q), and pcS-n and pcJ-n (n = 1, 2, 3, 4) bases, including the solvent effects described with explicit water molecules and/or the implicit Polarizable Continuum Model (PCM). The effect of molecular dynamics (MD) on NMR parameters was MD-calculated using the GAFF force field inclusive of explicit hydration with TIP3P water molecules. Both the optimal geometries and the dynamic behaviors of the DEP and cDEP phosphates differed notably, which allowed a reliable theoretical benchmark of the P NMR parameters fo...
Journal of Magnetic Resonance, 2012
Heterogeneous samples, such as soils, sediments, plants, tissues, foods and organisms, often contain liquid-, gel-and solid-like phases and it is the synergism between these phases that determine their environmental and biological properties. Studying each phase separately can perturb the sample, removing important structural information such as chemical interactions at the gel-solid interface, kinetics across boundaries and conformation in the natural state. In order to overcome these limitations a Comprehensive Multiphase-Nuclear Magnetic Resonance (CMP-NMR) probe has been developed, and is introduced here, that permits all bonds in all phases to be studied and differentiated in whole unaltered natural samples. The CMP-NMR probe is built with high power circuitry, Magic Angle Spinning (MAS), is fitted with a lock channel, pulse field gradients, and is fully susceptibility matched. Consequently, this novel NMR probe has to cover all HR-MAS aspects without compromising power handling to permit the full range of solution-, gel-and solid-state experiments available today. Using this technology, both structures and interactions can be studied independently in each phase as well as transfer/interactions between phases within a heterogeneous sample. This paper outlines some basic experimental approaches using a model heterogeneous multiphase sample containing liquid-, gel-and solid-like components in water, yielding separate 1 H and 13 C spectra for the different phases. In addition, 19 F performance is also addressed. To illustrate the capability of 19 F NMR soil samples, containing two different contaminants, are used, demonstrating a preliminary, but real-world application of this technology. This novel NMR approach possesses a great potential for the in situ study of natural samples in their native state.
Multinuclear solid-state NMR of inorganic materials
2002
Chapter headings. Preface. Introduction. Physical background. Experimental approaches. 29Si NMR. 27Al NMR. 17O NMR. NMR of other commonly studied nuclei. NMR of low-gamma nuclides. NMR of other spin-1/2 nuclei. NMR of other quadrupolar nuclei. Solid state NMR of metals and alloys.
Characterization of porous media structure by non linear NMR methods
In this paper we discuss the possibility of modifying the multiple spin echoes existing theory, developed for a homogeneous system, to describe also an inhomogeneous system such as a porous medium. We report here the first experimental application of MSE methods to materials like travertine. The ratio A 2 /A 1 from water in travertine presents minima for characteristic values of the delay time , like what was previously observed in the trabecular bone. By a judicious choice of the delay time and of the G gradient strength, the MSE sequence can be made sensitive to a specific length-scale of the sample heterogeneity. Furthermore the MSE image shows a particular new contrast that makes the non linear NMR method very attractive for the assessment of variations of the porous structure in porous systems.
Characterization of porous solids by NMR
Physical Review Letters, 1993
We are using a novel NMR method, that has been developed in our laboratory and employs the depression of the freezing point (AT,) of confined liquid within porous media, to investigate the effect of pre-drying silica with average pore diameter ranging from 60 A to 1000 A. Cyclohexane was the confined liquid. Pre-drying was found to affect only the smallest pores. A study to compare partially filled and over-filled samples showed that the average AT, for partially filled samples is greater than for over-filled. We have also investigated the use of water as the absorbed liquid and compared results with those obtained from cyclobexane studies. Reasonable agreement was found but cvclohexane was more sensitive. The method is fast and is suitable for monitoring pore size distributions in the range of 50-1000 A.
Solid-State NMR Study of an Open-Framework Aluminophosphate-Oxalate Hybrid
The Journal of Physical Chemistry B, 2003
Short-range order within a novel aluminophosphate-oxalate hybrid material with the unit cell formula [CH 2 (NH 3 )CH(NH 3 )CH 3 ] 2 [Al 4 P 6 O 20 (OH) 4 (C 2 O 4 )]H 2 O was studied by multinuclear solid-state NMR measurements. The 13 C, 27 Al, and 31 P MAS NMR spectra showed several resonance lines that could not be predicted by the single-crystal X-ray diffraction analysis. The underlying variety of carbon, aluminum, and phosphorus local environments was due to the nonuniform arrangement of the protonated 1,2diaminopropane species and water molecules residing within the pores of the open-framework material. 1 H → 13 C CPMAS NMR spectrum evidenced that the diaminopropane species either occupied two different positions or were present as two different isomers, which also gave rise to two slightly different deformations of one (P(3)O 4 ) of the three crystallographically distinct PO 4 tetrahedra. 1D 1 H and 31 P MAS and 2D 1 H → 31 P CP-MAS spectra revealed that the water molecule, occupying a well defined position within the pore with about 42% abundance, attracted H(2) from the hydroxyl group attached to the P(3) atom and involved the hydrogen atom into a strong hydrogen bond. The displacement of H(2) due to the interaction with the water molecule was determined by measuring H(2)-P(3) distances using 1 H → 31 P variable-contact-time CPMAS NMR experiments. As evidenced by 27 Al MAS and 3QMAS NMR spectra, the deformation of the P(3)O 4 tetrahedra by water and diaminopropane species further affected also local environments of the two proximal crystallographically inequivalent aluminum sites Al and Al(2).