Vibrational spectroscopy of single crystals of halide complexes.

Procedures are given for the experimentation of polarized single crystal Raman and far-infrared spectra which enable the symmetry species of bands to be identified. These procedures include orientation and preparation of crystals and the instrumentation of vibrational spectroscopy. The properties of single crystals such as refraction, double refraction, optical activity, and absorption are discussed where relevent to single crystal spectra. The basis of group theory in solids is explained and the method of factor group analysis is introduced. A simplified method of factor group analysis is reported which enables any crystal of known structure to be analysed using the tables of Appendices 1 and 2. This method is applied to the halide complexes studied by infrared and Raman spectroscopy. The vibrational spectra of single crystals of K2PtCl4 are reported. The infrared transmission spectra show that the in-plane bending mode can be unambiguously assigned a higher frequency than the out-of-plane bend. The vibrational spectra of the chlorine bridged chain compounds NMe4CdCl3, NH4CdCl3, H3NMeMnCl3, CsCuCl3, and CsMnCl3(H2O)2 are discussed in terms of both the chain and factor group symmetry. Many assignments are made. The single crystal Raman spectra of two series of hydrates M12CUC14(H2O)2 and M12MIIICl5(H2O), where or alkali metal and MIII=Fe or In, are reported. Some single crystal reflectance spectral data are also given and many of the bands are assigned.