期刊
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
卷 136, 期 -, 页码 107-112出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.saa.2013.08.117
关键词
Pyridoyl benzoyl beta-diketones; Isotope effects on C-13 chemical shifts; Solid state NMR; Coupling constants; DFT calculations
类别
资金
- INTAS [96-1021]
The tautomeric equilibria for 2-pyridoyl-, 3-pyridoyl-, and 4-pyridoyl-benzoyl methane have been investigated using deuterium isotope effects on H-1 and C-13 chemical shifts both in the liquid and the solid state. Equilibria are established both in the liquid and the solid state. In addition, in the solution state the 2-bond and 3-bond J(H-1-C-13) coupling constants have been used to confirm the equilibrium positions. The isotope effects due to deuteriation at the OH position are shown to be superior to chemical shift in determination of equilibrium positions of these almost symmetrical -pyridoyl-benzoyl methanes. The assignments of the NMR spectra are supported by calculations of the chemical shifts at the DFT level. The equilibrium positions are shown to be different in the liquid and the solid state. In the liquid state the 4-pyridoyl derivative is at the B-form (C-1 is OH), whereas the 2-and 3-pyridoyl derivatives are in the A-form. In the solid state all three compounds are on the B-form. The 4-pyridoyl derivative shows unusual deuterium isotope effects in the solid, which are ascribed to a change of the crystal structure of the deuteriated compound. (C) 2013 Elsevier B.V. All rights reserved.
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