Single Crystal Polarised Infrared and Laser Raman Studies of Some Inorganic Complexes

Single crystal polarized infra-red and Raman studies of some ionic transition metal complexes have been used to generate extremely accurate vibrational data, both with respect to frequency and symmetry assignments, and also investigate a variety of solid-state phenomena. The effects include static and dynamic crystal field splitting, order-disorder phenomena and first order pha. se transitions. Extensive infra-red and Raman studies were undertaken for those complexes having the general formula A2MX4 and A3MX5 both of which contain isolated MX4 2- tetrahedral ions. The spectra of these complexes clearly demonstrate the effects of distortion from perfect tetrahedral symmetry and both site and factor group splitting. In order to assist the assignment of a high frequency lattice mode, a Kramers-Kronig (K-K) analysis of the reflectivity data obtained from the A3MX5 complexes was undertaken. The Raman spectra of the complexes (RNH3)2MX4, (Me4N)MX4, (Et4N)2MX4 and (DMA)3 MX5 recorded at temperatures between 300 K and 77 K all show significant changes with temperature which can be attributed to orientational ordering of both the cations and anions. The (RNH3)2MX4 complexes contain square planar MX4 units which are linked together in 2-D sheets and hence their spectra differ from those characteristic of square-planar complexes. Most of the copper complexes studied exhibit thermochromic behaviour but the cause is not attributed to any form of structural phase transition. The single crystal Raman and infra-red reflectance spectra of some sodium perovskite fluorides having the GdFeO3 structure have been investigated. The reflectivity data was subjected both to K---K and classical dispersion analysis to obtain the dispersion parameters. From consideration both of the factor group predictions and Raman and infra-red data, the centrosymmetric space group D162h is confirmed these NaMF3 complexes. Raman and infra-red spectra of K2ZrF6 and K2HfF6 are discussed in terms of the linked MF8 dodecahedra in which both the zirconium and hafnium atoms are eight co-ordinate. Owing to experimental difficulties, the first order phase transitions reported for some perchlorate complexes could not be detected from an investigation of their vibrational spectra. Only the room temperature Raman spectra could be recorded