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International Journal of Spectroscopy
Volume 2013 (2013), Article ID 216518, 10 pages
http://dx.doi.org/10.1155/2013/216518
Research Article

Study of the Halogen Bonding between Pyridine and Perfluoroalkyl Iodide in Solution Phase Using the Combination of FTIR and 19F NMR

1Chemistry Department, Claflin University, Orangeburg, SC 29115, USA
2Chemistry Department, Furman University, Greenville, SC 29613, USA

Received 8 March 2013; Accepted 8 May 2013

Academic Editor: Rolf W. Berg

Copyright © 2013 Briauna Hawthorne et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Halogen bonding between pyridine and heptafluoro-2-iodopropane (iso-C3F7I)/heptafluoro-1-iodopropane (1-C3F7I) was studied using a combination of FTIR and 19F NMR. The ring breathing vibration of pyridine underwent a blue shift upon the formation of halogen bonds with both iso-C3F7I and 1-C3F7I. The magnitudes of the shifts and the equilibrium constants for the halogen-bonded complex formation were found to depend not only on the structure of the halocarbon, but also on the solvent. The halogen bond also affected the Cα-F (C-F bond on the center carbon) bending and stretching vibrations in iso-C3F7I. These spectroscopic effects show some solvent dependence, but more importantly, they suggest the possibility of intermolecular halogen bonding among iso-C3F7I molecules. The systems were also examined by 19F NMR in various solvents (cyclohexane, hexane, chloroform, acetone, and acetonitrile). NMR dilution experiments support the existence of the intermolecular self-halogen bonding in both iso-C3F7I and 1-C3F7I. The binding constants for the pyridine/perfluoroalkyl iodide halogen bonding complexes formed in various solvents were obtained through NMR titration experiments. Quantum chemical calculations were used to support the FTIR and 19F NMR observations.