Infrared Spectra of Charge-Transfer Complexes. VII. The Solid Benzene—Bromine Complex

Abstract

The infrared spectrum of the solid benzene—Br₂ complex has been measured to give the changes in frequency and an estimate of the changes in intensity from the pure benzene and pure Br₂ crystals. The complex was usually prepared by condensing a 1:1 mixture of benzene and bromine vapor onto a cold plate, but other techniques were also tried, and partial studies are reported. These spectra show definitely that neither the benzene nor bromine molecules in our samples are located on a site possessing a center of symmetry. From the analysis of the spectrum of the complexed benzene, a site symmetry of C_3v is deduced. This apparent contradiction of the results of the x‐ray studies of Strømme and Hassel is discussed and reconciled. The frequency shifts and intensity changes on complex formation are discussed in some detail.