Proton Transfer in Strong Hydrogen Bonds Revealed by Infrared Spectra - Correlations between Structure and Spectra for the BrH : NH3 Complex

K. Szczepaniak and W.B. Person Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida, 32611, USA

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Received: 26 10 2007;

Our scope is to achieve an understanding of the relation between the infrared spectrum and structure of a strong hydrogen-bonded complex, BrH : NH3, and how and why this relationship is affected by the environment surrounding the complex. A series of DFT/B3LYP/6-31G(d,p) calculations was carried out for this system to obtain its structure and spectrum in different dielectric fields characterized by their relative permittivities. Changes in structure and spectrum (both frequencies and intensities) as the relative permittivity changes are explored. Calculations of spectra are made first under the harmonic approximation. In the next step the effect of anharmonicity was estimated for several different dielectric fields. The calculated anharmonic spectrum (for εr = 1.6) is compared with the experimentally observed infrared spectrum of the complex isolated in an Ar matrix at 10 K, obtained in our laboratory. The calculated frequencies and relative intensities for all normal modes agree with the corresponding experimental data surprisingly well. The potential usefulness of structure-spectra correlations is explored.

DOI: 10.12693/APhysPolA.112.S-19 PACS numbers: 82.30.Rs, 33.20.Ea, 33.70.Fd, 31.15.Ew, 33.20.Tp