Distribution effects on 1H double-quantum MAS NMR spectra

J Magn Reson. 2004 Mar;167(1):161-7. doi: 10.1016/j.jmr.2003.12.008.

Abstract

The effect of a distribution in the (1)H-(1)H dipolar coupling on (1)H double-quantum (DQ) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spinning sideband patterns is considered. In disordered or amorphous materials a distribution in the magnitude of the (1)H-(1)H dipolar coupling is a realistic possibility. Simulations of the (1)H DQ MAS NMR spinning sideband spectra were performed with the two-spin approximation. These simulations reveal that a dipolar coupling distribution can greatly affect the DQ spectral shape and behavior of the DQ build-up. The spectral line shapes are quantified by measurement of the relative intensities of the DQ sidebands. These variations in the (1)H DQ NMR spectra are evaluated as a function of the width of the dipolar coupling distribution. As an example, the experimental DQ spinning sideband spectrum for a hydrated polyoxoniobate containing 15 H(2)O molecules per hexaniobate cluster, are better simulated with a distribution of dipolar couplings opposed to a single coupling constant.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Validation Study

MeSH terms

  • Computer Simulation
  • Magnetic Resonance Spectroscopy / methods*
  • Models, Chemical*
  • Models, Statistical*
  • Niobium / analysis*
  • Niobium / chemistry*
  • Protons
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Sodium / analysis*
  • Sodium / chemistry*
  • Spin Labels*

Substances

  • Protons
  • Spin Labels
  • sodium hexaniobate
  • Niobium
  • Sodium