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Title: Two-dimensional NMR measurement and point dipole model prediction of paramagnetic shift tensors in solids

A new two-dimensional Nuclear Magnetic Resonance (NMR) experiment to separate and correlate the first-order quadrupolar and chemical/paramagnetic shift interactions is described. This experiment, which we call the shifting-d echo experiment, allows a more precise determination of tensor principal components values and their relative orientation. It is designed using the recently introduced symmetry pathway concept. A comparison of the shifting-d experiment with earlier proposed methods is presented and experimentally illustrated in the case of {sup 2}H (I = 1) paramagnetic shift and quadrupolar tensors of CuCl{sub 2}⋅2D{sub 2}O. The benefits of the shifting-d echo experiment over other methods are a factor of two improvement in sensitivity and the suppression of major artifacts. From the 2D lineshape analysis of the shifting-d spectrum, the {sup 2}H quadrupolar coupling parameters are 〈C{sub q}〉 = 118.1 kHz and 〈η{sub q}〉 = 0.88, and the {sup 2}H paramagnetic shift tensor anisotropy parameters are 〈ζ{sub P}〉 = − 152.5 ppm and 〈η{sub P}〉 = 0.91. The orientation of the quadrupolar coupling principal axis system (PAS) relative to the paramagnetic shift anisotropy principal axis system is given by (α,β,γ)=((π)/2 ,(π)/2 ,0). Using a simple ligand hopping model, the tensor parameters in the absence of exchange are estimated. Onmore » the basis of this analysis, the instantaneous principal components and orientation of the quadrupolar coupling are found to be in excellent agreement with previous measurements. A new point dipole model for predicting the paramagnetic shift tensor is proposed yielding significantly better agreement than previously used models. In the new model, the dipoles are displaced from nuclei at positions associated with high electron density in the singly occupied molecular orbital predicted from ligand field theory.« less
Authors:
; ;  [1] ;  [2] ;  [3]
  1. Department of Chemistry, Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210 (United States)
  2. Department of Physics, Dr. H. S. Gour University, Sagar, Madhya Pradesh 470003 (India)
  3. Division of Natural Science, Mathematics, and Nursing, Berea College, Berea, Kentucky 40403 (United States)
Publication Date:
OSTI Identifier:
22415452
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 1; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANISOTROPY; COMPARATIVE EVALUATIONS; COPPER CHLORIDES; COUPLING; DEUTERIUM; DIPOLES; ELECTRON DENSITY; FIELD THEORIES; HEAVY WATER; KHZ RANGE; LIGANDS; MOLECULAR ORBITAL METHOD; NMR SPECTRA; NUCLEAR MAGNETIC RESONANCE; PARAMAGNETISM; SOLIDS; TENSORS; TWO-DIMENSIONAL SYSTEMS