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NMR Studies of Solid Pentachlorophenol-4-Methylpyridine Complexes Exhibiting Strong OHN Hydrogen Bonds: Geometric H/D Isotope Effects and Hydrogen Bond Coupling Cause Isotopic Polymorphism

Ip, B. C. K. ; Shenderovich, I. G. ; Tostoy, P. M. ; Frydel, J. ; Denisov, G. S. ; Buntkowsky, G. ; Limbach, H. H. (2012)
NMR Studies of Solid Pentachlorophenol-4-Methylpyridine Complexes Exhibiting Strong OHN Hydrogen Bonds: Geometric H/D Isotope Effects and Hydrogen Bond Coupling Cause Isotopic Polymorphism.
In: Journal of Physical Chemistry A, 116 (46)
Article, Bibliographie

Abstract

We have studied the hydrogen bond interactions of N-15 labeled 4-methylpyridine (4-MP)with pentachlorophenol (PCP) in the solid state and in polar solution Using various NMR techniques. Previous spectroscopic, X-ray, and neutron crystallographic studies showed that the triclinic 1:1 complex (4-MPPCP) exhibits the strongest known intermolecular. OHN hydrogen bond in the solid state. By contrast, deuteration of the hydrogen bond gives rise to the formation of a monoclinic structure exhibiting a weaker hydrogen bond. By performing NMR experiments at different deuterium fractions and taking advantage of dipolar H-1-N-15 recoupling under combined fast MAS and H-1 decoupling, we provide an explanation of the origin of the isotopic polymorphism of 4-MPPCP and improve previous chemical shift correlations for OHN hydrogen bonds. Because of anharmonic ground state vibrations, an ODN hydrogen bond in the triclinic form exhibits a shorter oxygen-hydron and a longer oxygen-nitrogen distance as compared to surrounding OHN hydrogen bonds, which also implies a reduction of the local dipole moment. The dipole-dipole interaction between adjacent coupled OHN hydrogen bonds which determines the structure of triclinic 4-MPPCP is then reduced by deuteration, and other interactions become dominant, leading to the monoclinic form. Finally, the observation of stronger OHN hydrogen bonds by H-1 NMR in polar solution as compared to the solid state is discussed.

Item Type: Article
Erschienen: 2012
Creators: Ip, B. C. K. ; Shenderovich, I. G. ; Tostoy, P. M. ; Frydel, J. ; Denisov, G. S. ; Buntkowsky, G. ; Limbach, H. H.
Type of entry: Bibliographie
Title: NMR Studies of Solid Pentachlorophenol-4-Methylpyridine Complexes Exhibiting Strong OHN Hydrogen Bonds: Geometric H/D Isotope Effects and Hydrogen Bond Coupling Cause Isotopic Polymorphism
Language: English
Date: 2012
Journal or Publication Title: Journal of Physical Chemistry A
Volume of the journal: 116
Issue Number: 46
URL / URN: http://apps.webofknowledge.com/full_record.do?product=WOS&se...
Abstract:

We have studied the hydrogen bond interactions of N-15 labeled 4-methylpyridine (4-MP)with pentachlorophenol (PCP) in the solid state and in polar solution Using various NMR techniques. Previous spectroscopic, X-ray, and neutron crystallographic studies showed that the triclinic 1:1 complex (4-MPPCP) exhibits the strongest known intermolecular. OHN hydrogen bond in the solid state. By contrast, deuteration of the hydrogen bond gives rise to the formation of a monoclinic structure exhibiting a weaker hydrogen bond. By performing NMR experiments at different deuterium fractions and taking advantage of dipolar H-1-N-15 recoupling under combined fast MAS and H-1 decoupling, we provide an explanation of the origin of the isotopic polymorphism of 4-MPPCP and improve previous chemical shift correlations for OHN hydrogen bonds. Because of anharmonic ground state vibrations, an ODN hydrogen bond in the triclinic form exhibits a shorter oxygen-hydron and a longer oxygen-nitrogen distance as compared to surrounding OHN hydrogen bonds, which also implies a reduction of the local dipole moment. The dipole-dipole interaction between adjacent coupled OHN hydrogen bonds which determines the structure of triclinic 4-MPPCP is then reduced by deuteration, and other interactions become dominant, leading to the monoclinic form. Finally, the observation of stronger OHN hydrogen bonds by H-1 NMR in polar solution as compared to the solid state is discussed.

Uncontrolled Keywords: low-temperature nmr acid-base complexes inelastic neutron-scattering nuclear-magnetic-resonance state nmr low-barrier chemical-shifts proton-transfer o-h model systems
Additional Information:

042GT Times Cited:11 Cited References Count:109

Divisions: 07 Department of Chemistry
07 Department of Chemistry > Eduard Zintl-Institut > Physical Chemistry
Date Deposited: 27 Oct 2014 20:43
Last Modified: 29 May 2019 09:17
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