The Dimers of Fluorinated Benzenes with Water:
Microwave Spectra and Internal Motion Analyses.
Heinrich Mäder
Institut für Physikalische Chemie, Universität Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
Kai Brendel and Wolfgang Jäger
Department of Chemistry, University of Alberta, Edmonton AB T6G 2G2, Canada
As water is the most important solvent occuring in nature its dimers with organic compounds are of special interest and the analysis of the interaction between water and organic compounds is a first step towards an understanding of solvation processes. Information about the structure and internal dynamics of such complexes is contained in their rotational spectra. Using the techniques of molecular beam FT microwave spectroscopy, we recently studied the complexes of water with fluorobenzene and 1,4-difluorobenzene. In the rotational spectra of the normal species of both dimers a characteristic splitting of rotational lines was observed and is attributed to an internal motion of the water moiety within the complex. The intensity ratios of approximately 1:3 of the corresponding components suggest an internal tunneling motion that permutes the two water hydrogen atoms. To analyze this motion, a flexible model, guided by ab initio calculations on the MP2 and CCSD(T) level of theory, was applied. Results of this analysis, rotational constants and structures will be presented.