title: NMR parameters and geometries of OHN and ODN hydrogen bonds of pyridine-acid complexes.
abstract: In this paper, equations are proposed which relate various NMR parameters of OHN hydrogen-bonded pyridine-acid complexes to their bond valences which are in turn correlated with their hydrogen-bond geometries. As the valence bond model is strictly valid only for weak hydrogen bonds appropriate empirical correction factors are proposed which take into account anharmonic zero-point energy vibrations. The correction factors are different for OHN and ODN hydrogen bonds and depend on whether a double or a single well potential is realized in the strong hydrogen-bond regime. One correction factor was determined from the known experimental structure of a very strong OHN hydrogen bond between pentachlorophenol and 4-methylpyridine, determined by the neutron diffraction method. The remaining correction factors which allow one also to describe H/D isotope effects on the NMR parameters and geometries of OHN hydrogen bond were determined by analysing the NMR parameters of the series of protonated and deuterated pyridine- and collidine-acid complexes. The method may be used in the future to establish hydrogen-bond geometries in biologically relevant functional OHN hydrogen bonds.
authors.affiliation: Institut für Chemie, Freie Universität Berlin, Takustrasse 3, Berlin, Germany. limbach@chemie.fu-berlin.de <limbach@chemie.fu-berlin.de>
authors.forename: Hans-Heinrich
authors.initials: HH
authors.lastname: Limbach
authors.forename: Mariusz
authors.initials: M
authors.lastname: Pietrzak
authors.forename: Shasad
authors.initials: S
authors.lastname: Sharif
authors.forename: Peter M
authors.initials: PM
authors.lastname: Tolstoy
authors.forename: Ilya G
authors.initials: IG
authors.lastname: Shenderovich
authors.forename: Sergei N
authors.initials: SN
authors.lastname: Smirnov
authors.forename: Nikolai S
authors.initials: NS
authors.lastname: Golubev
authors.forename: Gleb S
authors.initials: GS
authors.lastname: Denisov
mesh_terms: D000143:Acids / Q000737:chemistry*; D003903:Deuterium / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D014732:Vibration
chemical_list: D000143:Acids; D011725:Pyridines; D006859:Hydrogen; D003903:Deuterium; D009584:Nitrogen; C023666:pyridine; D010100:Oxygen