title: Quantifying the Effects of Halogen Bonding by Haloaromatic Donors on the Acceptor Pyrimidine.
abstract: The effects of intermolecular interactions by a series of haloaromatic halogen bond donors on the normal modes and chemical shifts of the acceptor pyrimidine are investigated by Raman and NMR spectroscopies and electronic structure computations. Halogen-bond interactions with pyrimidine's nitrogen atoms shift normal modes to higher energy and upfield shift1H and13C NMR peaks in adjacent nuclei. This perturbation of vibrational normal modes is reminiscent of the effects of hydrogen bonded networks of water, methanol, or silver on pyrimidine. The unexpected observation of vibrational red shifts and downfield13C NMR shifts in some complexes suggests that other intermolecular forces such as π interactions are competing with halogen bonding. Natural bond orbital analyses indicate a wide range of charge transfer is possible from pyrimidine to different haloaromatic donors and computed halogen bond binding energies can be larger than a typical hydrogen bond. These results emphasize the importance in strategic selection of substituents and electron withdrawing groups in developing supramolecular structures based on halogen bonding.
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, MS, 38677, USA.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Ellington
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, MS, 38677, USA.
authors.forename: Peyton L
authors.initials: PL
authors.lastname: Reves
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, MS, 38677, USA.
authors.forename: Briana L
authors.initials: BL
authors.lastname: Simms
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, MS, 38677, USA.
authors.forename: Jamey L
authors.initials: JL
authors.lastname: Wilson
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, MS, 38677, USA.
authors.forename: Davita L
authors.initials: DL
authors.lastname: Watkins
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, MS, 38677, USA.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Tschumper
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, MS, 38677, USA.
authors.forename: Nathan I
authors.identifier: http://orcid.org/0000-0002-6221-2709
authors.initials: NI
authors.lastname: Hammer
keywords: NMR spectroscopyRaman spectroscopy; ab initio calculations; halogen bonding; vibrational spectroscopy