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Intramolecular hydrogen bond and proton transfer in 3-(2-benzimidazolylthio)-2,4-pentanedione. Crystallographic evidence and theoretical calculations

Lubomir Smrcok ; Daniel Tunega ; Vratislav Langer (Institutionen för oorganisk miljökemi) ; Miroslav Koóš
Zeitschrift für Kristallographie (0044-2968 ). Vol. 217 (2002), 5, p. 217-222.
[Artikel, refereegranskad vetenskaplig]

Crystal structure of the title compound is orthorhombic, Pbca, a=7.8689(2)Å, b=9.6519(3)Å, c=31.3579(9)Å. The structure was solved by direct methods and refined by a full-matrix least squares procedure to final R (all)=0.0682 for 2853 unique diffractions merged from 24459 measured at 183(2)K. The molecule is formed by two planar moieties joined through an atom of sulphur. The short intramolecular O...O contact is 2.430(2)Å, the intramolecular hydrogen bond is slightly asymmetric. Theoretical ab initio calculations done at B3LYP/SVP and ONIOM(MP2/SVP:B3LYP/SVP) levels showed that the experimental geometry of pentanedione pseudoring is close to the geometry corresponding to a transition state on the asymmetric potential energy curve. Calculated energy difference between two minima is only –4.72 kJ/mol and the energy barrier –6.02 kJ/mol, which agrees well to ~6.6kJ/mol found in microwave spectroscopic study of malonaldehyde.

Nyckelord: X-ray diffraction, crystal structure, intramolecular hydrogen bond



Denna post skapades 2006-08-29. Senast ändrad 2013-05-15.
CPL Pubid: 9765

 

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