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

Brenda C.K. Ip, Ilya G. Shenderovich, Peter M. Tolstoy, Jaroslaw Frydel, Gleb S. Denisov, Gerd Buntkowsky, Hans Heinrich Limbach

Результат исследований: Научные публикации в периодических изданияхстатьярецензирование

40 Цитирования (Scopus)

Аннотация

We have studied the hydrogen bond interactions of 15 N 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 1 H- 15 N recoupling under combined fast MAS and 1 H 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 1 H NMR in polar solution as compared to the solid state is discussed.

Язык оригиналаанглийский
Страницы (с-по)11370-11387
Число страниц18
ЖурналJournal of Physical Chemistry A
Том116
Номер выпуска46
DOI
СостояниеОпубликовано - 26 ноя 2012

Предметные области Scopus

  • Физическая и теоретическая химия

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