Interactions between the chloride anion and aromatic molecules: infrared spectra of the Cl-_C6H5CH3, Cl-_C6H5NH2 and Cl-_C6H5OH complexes

Authors

Corinna Emmeluth, University Of Melbourne
Berwyck L. J Poad, University of WollongongFollow
Christopher D. Thompson, University Of Melbourne
Evan J. Bieske, University Of Melbourne

RIS ID

72195

Publication Details

Emmeluth, C., Poad, B. L. J., Thompson, C. D. & Bieske, E. J. (2007). Interactions between the chloride anion and aromatic molecules: infrared spectra of the Cl^-_C₆H₅CH₃, Cl^-_C₆H₅NH₂ and Cl^-_C₆H₅OH complexes. The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory, 111 (31), 7322-7328.

Abstract

The Cl^-−C₆H₅CH₃·Ar, Cl^-−C₆H₅NH₂·Ar, and Cl^-−C₆H₅OH·Ar anion complexes are investigated using infrared photodissociation spectroscopy and ab initio calculations at the MP2/aug-cc-pVDZ level. The results indicate that for Cl^-−C₆H₅NH₂ and Cl^-−C₆H₅OH, the Cl^- anion is attached to the substituent group by a single near-linear hydrogen bond. For Cl^-−C₆H₅CH₃, the Cl^- is attached to an ortho-hydrogen atom on the aromatic ring and to a hydrogen atom on the methyl group by a weaker hydrogen bond. The principal spectroscopic consequence of the hydrogen-bonding interaction in the three complexes is a red-shift and intensity increase for the CH, NH, and OH stretching modes. Complexities in the infrared spectra in the region of the hydrogen-bonded XH stretch band are associated with Fermi resonances between the hydrogen-stretching vibrational modes and bending overtone and combination levels. There are notable correlations between the vibrational red-shift, the elongation of the H-bonded XH group, and the proton affinity of the aromatic molecule's conjugate base.