Anisotropy and NMR spectroscopy

Abstract

In this paper, different aspects concerning anisotropy in Nuclear Magnetic Resonance (NMR) spectroscopy have been reviewed. In particular, the relevant theory has been presented, showing how anisotropy stems from the dependence of internal nuclear spin interactions on the molecular orientation with respect to the external magnetic field direction. The consequences of anisotropy in the use of NMR spectroscopy have been critically discussed: on one side, the availability of very detailed structural and dynamic information, and on the other side, the loss of spectral resolution. The experiments used to measure the anisotropic properties in solid and soft materials, where, in contrast to liquids, such properties are not averaged out by the molecular tumbling, have been described. Such experiments can be based either on static low-resolution techniques or on one- and two-dimensional pulse sequences exploiting Magic Angle Spinning (MAS). Examples of applications of NMR spectroscopy have been shown, which exploit anisotropy to obtain important physico-chemical information on several categories of systems, including pharmaceuticals, inorganic materials, polymers, liquid crystals, and self-assembling amphiphiles in water. Solid-state NMR spectroscopy can be considered, nowadays, one of the most powerful characterization techniques for all kinds of solid, either amorphous or crystalline, and semi-solid systems for the obtainment of both structural and dynamic properties on a molecular and supra-molecular scale. Graphic abstract

Impact of thermal treatment on the Li-ion transport, interfacial properties, and composite preparation of LLZO garnets for solid-state electrolytes

“…In general, the linewidth (FWHM) of 7 Li NMR signals is directly related to ion dynamics, as faster ion motions can effectively average out the anisotropic interactions present in the solid state, 38,39 reducing the observed linewidths. Fig.…”

Thermal, structural and dynamic properties of ionic liquids and organic ionic plastic crystals with a small ether-functionalised cation

“…CSA powder patterns result from the superposition of multiple peaks generated from the anions orientated isotropically with respect to the magnetic field. 93 We attribute the complex 19 F spectra to the formation of much larger, bulky crystallites, resulting in a finite number of crystal orientations. Cooling the material to phase II resulted in the return to a homogenous material with the long-range structural ordering of anions in the sublattice, seen by a symmetric peak (FHWM at 30 1C was 15.8 kHz).…”

Breakdown of thermalization in spin chains with single-ion anisotropy

“…In this paper, we investigate localization of quantum states in a J 1 − J 2 model in the presence of a non-uniform magnetic field, and incorporating an additional term to address uniaxial single-ion anisotropy, which naturally arises in magnetic models with S ≥ 1/2 [76][77][78]. By employing numerically exact diagonalization, we calculate the temporal evolution of complementary quantifiers, namely imbalance, entanglement entropy, and participation entropy.…”