Acta Crystallographica Section B

Structural Science

Volume 61, Part 6 (December 2005)

research papers

Acta Cryst. (2005). B61, 724-730 [ doi:10.1107/S0108768105030077 ]

Variable-temperature neutron diffraction studies of the short, strong hydrogen bonds in the crystal structure of pyridine-3,5-dicarboxylic acid

J. A. Cowan, J. A. K. Howard, G. J. McIntyre, S. M.-F. Lo and I. D. Williams

Abstract: Pyridine-3,5-dicarboxylic acid has been studied by single-crystal neutron diffraction at 15 and 296 K. Pyridine-3,5-dicarboxylic acid, in which the carboxylic acid protons have been replaced by deuterons, has also been studied at 15, 150 and 296 K. The protonated structure contains a short NHO hydrogen bond [NO 2.523 (2) Å at 15 K]. Temperature-dependent proton migration occurs where the N-H distance in the hydrogen bond changes from 1.213 (4) Å at 15 K to 1.308 (6) Å at 300 K. In the deuterated structure the overall hydrogen-bond length increased [NO 2.538 (3) Å at 15 K] and the magnitude of the migration increased so that the N-D distance changes from 1.151 (3) Å at 15 K to 1.457 (4) Å at 300 K.

Keywords: variable-temperature neutron diffraction; hydrogen bonding; deuterated structure; proton migration.


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