STRUCTURE OF THE SEVOFLURANE-BENZENE COMPLEX AS DETERMINED BY CHIRPED-PULSE FTMW SPECTROSCOPY

Abstract

Following previous microwave studies on sevoflurane monomer by Suenram \textit{et al.} and Vega-Toribio \textit{et al.} we report the broadband rotational spectrum of sevoflurane clustered with benzene. The structure assigned is consistent with a C-H$\cdots\pi$ interaction between the benzene ring and the (CF$_3$)$_2$C-H hydrogen on sevoflurane. The spectrum of this species is complicated by the six-fold internal rotation of the benzene ring over the C$_1$ framework of sevoflurane. The six-fold tunneling falls into a high effective barrier case where there are several bound torsional levels. The tunneling spectrum has been successfully analyzed using the BELGI internal rotation program and a barrier to internal rotation of the benzene against sevoflurane of 32.5 cm$^{-1}$ has been determined. Structural information about the complex has been obtained by studying the complex of sevoflurane with benzene-\textit{d$_1$}. For this complex, six unique isomers are observed making it possible to determine the positions of the benzene H-atoms in the complex. Combination of these hydrogen r$_s$ positions with the sevoflurane monomer r$_s$ coordinates reported by Lesarri \textit{et al.} results in a substitution structure in excellent agreement with the ab initio results. Finally, initial microwave results on two sevoflurane dimer species will also be presented.