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Proton magnetic shielding tensor in liquid water

Modig, Kristofer LU and Halle, Bertil LU (2002) In Journal of the American Chemical Society 124(40). p.12031-12041
Abstract
The nuclear magnetic shielding tensor is a sensitive probe of the local electronic environment, providing information about molecular structure and intermolecular interactions. The magnetic shielding tensor of the water proton has been determined in hexagonal ice, but in liquid water, where the tensor is isotropically averaged by rapid molecular tumbling, only the trace of the tensor has been measured. We report here the first determination of the proton shielding anisotropy in liquid water, which, when combined with chemical shift data, yields the principal shielding components parallel (sigma(parallel to)) and perpendicular (sigma(perpendicular to)) to the O-H bond. We obtained the shielding anisotropy sigma(parallel to) -... (More)
The nuclear magnetic shielding tensor is a sensitive probe of the local electronic environment, providing information about molecular structure and intermolecular interactions. The magnetic shielding tensor of the water proton has been determined in hexagonal ice, but in liquid water, where the tensor is isotropically averaged by rapid molecular tumbling, only the trace of the tensor has been measured. We report here the first determination of the proton shielding anisotropy in liquid water, which, when combined with chemical shift data, yields the principal shielding components parallel (sigma(parallel to)) and perpendicular (sigma(perpendicular to)) to the O-H bond. We obtained the shielding anisotropy sigma(parallel to) - sigma(perpendicular to) by measuring the proton spin relaxation rate as a function of magnetic induction field in a water sample where dipole-dipole couplings are suppressed by H/D isotope dilution. The temperature dependence of the shielding components, determined from 0 to 80 degreesC, reflects vibrational averaging over a distribution of instantaneous hydrogen-bond geometries in the liquid and thus contains unique information about the temperature-dependent structure of liquid water. The temperature dependence of the shielding anisotropy is found to be 4 times stronger than that of the isotropic shielding. We analyze the liquid water shielding components in the light of previous NMR and theoretical results for vapor and ice. We show that a simple two-state model of water structure fails to give a consistent interpretation of the shielding data and we argue that a more detailed analysis is needed that quantitatively relates the shielding components to hydrogen bond geometry. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of the American Chemical Society
volume
124
issue
40
pages
12031 - 12041
publisher
The American Chemical Society
external identifiers
  • wos:000178487100040
  • scopus:0037048626
ISSN
1520-5126
DOI
10.1021/ja026981s
language
English
LU publication?
yes
id
81569822-0f46-4d49-a4b8-ef22c3b0cfc2 (old id 325573)
date added to LUP
2007-11-16 10:46:51
date last changed
2017-10-01 04:53:25
@article{81569822-0f46-4d49-a4b8-ef22c3b0cfc2,
  abstract     = {The nuclear magnetic shielding tensor is a sensitive probe of the local electronic environment, providing information about molecular structure and intermolecular interactions. The magnetic shielding tensor of the water proton has been determined in hexagonal ice, but in liquid water, where the tensor is isotropically averaged by rapid molecular tumbling, only the trace of the tensor has been measured. We report here the first determination of the proton shielding anisotropy in liquid water, which, when combined with chemical shift data, yields the principal shielding components parallel (sigma(parallel to)) and perpendicular (sigma(perpendicular to)) to the O-H bond. We obtained the shielding anisotropy sigma(parallel to) - sigma(perpendicular to) by measuring the proton spin relaxation rate as a function of magnetic induction field in a water sample where dipole-dipole couplings are suppressed by H/D isotope dilution. The temperature dependence of the shielding components, determined from 0 to 80 degreesC, reflects vibrational averaging over a distribution of instantaneous hydrogen-bond geometries in the liquid and thus contains unique information about the temperature-dependent structure of liquid water. The temperature dependence of the shielding anisotropy is found to be 4 times stronger than that of the isotropic shielding. We analyze the liquid water shielding components in the light of previous NMR and theoretical results for vapor and ice. We show that a simple two-state model of water structure fails to give a consistent interpretation of the shielding data and we argue that a more detailed analysis is needed that quantitatively relates the shielding components to hydrogen bond geometry.},
  author       = {Modig, Kristofer and Halle, Bertil},
  issn         = {1520-5126},
  language     = {eng},
  number       = {40},
  pages        = {12031--12041},
  publisher    = {The American Chemical Society},
  series       = {Journal of the American Chemical Society},
  title        = {Proton magnetic shielding tensor in liquid water},
  url          = {http://dx.doi.org/10.1021/ja026981s},
  volume       = {124},
  year         = {2002},
}