title: Experimental and theoretical 17O NMR study of the influence of hydrogen-bonding on C=O and O-H oxygens in carboxylic solids.
abstract: A systematic solid-state 17O NMR study of a series of carboxylic compounds, maleic acid, chloromaleic acid, KH maleate, KH chloromaleate, K2 chloromaleate, and LiH phthalate.MeOH, is reported. Magic-angle spinning (MAS), triple-quantum (3Q) MAS, and double angle rotation (DOR) 17O NMR spectra were recorded at high magnetic fields (14.1 and 18.8 T). 17O MAS NMR for metal-free carboxylic acids and metal-containing carboxylic salts show featured spectra and demonstrate that this combined, where necessary, with DOR and 3QMAS, can yield site-specific information for samples containing multiple oxygen sites. In addition to 17O NMR spectroscopy, extensive quantum mechanical calculations were carried out to explore the influence of hydrogen bonding at these oxygen sites. B3LYP/6-311G++(d,p) calculations of 17O NMR parameters yielded good agreement with the experimental values. Linear correlations are observed between the calculated 17O NMR parameters and the hydrogen bond strengths, suggesting the possibility of estimating H-bonding information from 17O NMR data. The calculations also revealed intermolecular H-bond effects on the 17O NMR shielding tensors. It is found that the delta11 and delta22 components of the chemical shift tensor at O-H and C=O, respectively, are aligned nearly parallel with the strong H-bond and shift away from this direction as the H-bond interaction weakens.
authors.affiliation: Department of Physics, University of Warwick, Coventry, CV4 7AL, U. K.
authors.forename: Alan
authors.initials: A
authors.lastname: Wong
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Pike
authors.forename: Rob
authors.initials: R
authors.lastname: Jenkins
authors.forename: Guy J
authors.initials: GJ
authors.lastname: Clarkson
authors.forename: Tiit
authors.initials: T
authors.lastname: Anupõld
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Howes
authors.forename: David H G
authors.initials: DH
authors.lastname: Crout
authors.forename: Ago
authors.initials: A
authors.lastname: Samoson
authors.forename: Ray
authors.initials: R
authors.lastname: Dupree
authors.forename: Mark E
authors.initials: ME
authors.lastname: Smith
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010100:Oxygen / Q000737:chemistry*; D010103:Oxygen Isotopes
chemical_list: D002264:Carboxylic Acids; D010103:Oxygen Isotopes; D010100:Oxygen