Hyperfine interactions and lattice dynamics of ferrocene, ring-substituted ferrocenes and their oxidation products

Using Fe-57 Mossbauer spectroscopy over the range 90 less than or equal to T less than or equal to 290 K, the isomer shift (IS) and quadrupole splitting (QS) hyperfine parameters have been determined for ferrocene and a number of ring-substituted ferrocenes, as well as for their cationic oxidation products, in order to elucidate the temperature dependencies of these parameters for such complexes. As noted previously, the IS is not sensitive to ring substitution, but its temperature dependence can be used to estimate an ''effective vibrating mass'' (M-eff) as probed by the resonance effect. In conjunction with the temperature dependence of the recoil-free fraction, it is Possible to estimate a ''Mossbauer lattice temperature'', (Theta(M)), for these solids. The QS parameter is temperature insensitive over the cited range for all of the neutral complexes. The cationic species give rise to a broad resonance which can be understood in terms of a spin 1/2 relaxation which is fast on the Mossbauer time scale. The temperature dependencies of the IS and recoil-free fraction for these relaxation spectra are also reported in detail.