title: 1H CSA parameters by ultrafast MAS NMR: Measurement and applications to structure refinement.
abstract: A1H anisotropic-isotropic chemical shift correlation experiment which employs symmetry-based recoupling sequences to reintroduce the chemical shift anisotropy in ν1and ultrafast MAS to resolve1H sites in ν2is described. This experiment is used to measure1H shift parameters for L-ascorbic acid, a compound with a relatively complex hydrogen-bonding network in the solid. The1H CSAs of hydrogen-bonded sites with resolved isotropic shifts can be extracted directly from the recoupled lineshapes. In combination with DFT calculations, hydrogen positions in crystal structures obtained from X-ray and neutron diffraction are refined by comparison with simulations of the full two-dimensional NMR spectrum. The improved resolution afforded by the second dimension allows even unresolved hydrogen-bonded sites1H to be assigned and their shift parameters to be obtained.
authors.affiliation: School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
authors.forename: Habeeba K
authors.initials: HK
authors.lastname: Miah
authors.affiliation: School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
authors.forename: Rosalie
authors.initials: R
authors.lastname: Cresswell
authors.affiliation: UK 850 MHz Solid-state NMR Facility, Department of Physics, Millburn House, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: Dinu
authors.initials: D
authors.lastname: Iuga
authors.affiliation: UK 850 MHz Solid-state NMR Facility, Department of Physics, Millburn House, University of Warwick, Coventry CV4 7AL, UK. Electronic address: Jeremy.Titman@nottingham.ac.uk.
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Titman