title: Deuterium quadrupolar tensors of L-histidine hydrochloride monohydrate-d7.
abstract: A deuterium NMR study at 14 T of a single crystal of L-histidine hydrochloride monohydrate has determined the deuteron quadrupole coupling constants CQ, asymmetry parameters eta, and electric field gradient orientation for the imidazolium and primary ammonium groups and for a water of crystallization. The imidazolium deuterons, which have very long relaxation times, have quite different coupling constants, reflecting different hydrogen bonding but nearly identical orientations, with the most distinct principal axis in both cases nearly parallel to the N-D vector. The -ND3 groups undergo 3-fold hops about the C-N bond axis and have typical quadrupole couplings; the D2O undergoes 2-fold hops, leading to a tensor with a large asymmetry parameter. With appropriate corrections for vibrational averaging, density functional cluster calculations give an excellent fit to the imidazolium tensor magnitudes and orientations.
authors.affiliation: Department of Chemistry, University of Nebraska at Lincoln, Lincoln, Nebraska 68588-0304, USA.
authors.forename: Xingang
authors.initials: X
authors.lastname: Zhao
authors.forename: Gerard S
authors.initials: GS
authors.lastname: Harbison
mesh_terms: D003903:Deuterium / Q000737:chemistry*; D006639:Histidine / Q000031:analogs & derivatives / Q000737:chemistry* / Q000378:metabolism; D006851:Hydrochloric Acid / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D006639:Histidine; D003903:Deuterium; D006851:Hydrochloric Acid