Ferrocene, Mossbauer parameters

Table 5. Selected Mossbauer parameters for ferrocene and various open ferrocenes (mm/s)...

The Mossbauer parameters of dppf complexes are collected in Table 1-4. Consistent with other ferrocenylphosphines [75], dppf shows a reduced quadrupole splitting compared with that of ferrocene (2.33 vs. 2.42 mm s ). On complexation, the isomer... 

Linear, saturated, polymers obtained by radical initiation of 1,1 -divinylferrocene hive the Mossbauer parameters (6, 0.23 mm s l LEq, 2.29 mm s l) expected for cyclopolymer8 with three-carbon bridged ferrocene units in the main chain. However, cationic initiation yields polymers which exhibit differences from the radical polymers in Mossbauer (, 0.27 mm s 7 Eq, 2.40 ntn s 7) and other spectroscopic studies. The cationic polymers may contain a bicyclic unit or a ladder structure in the chain. 

These results therefore indicate that the soluble, saturated polymers produced by radical initiation of DVF are cyclopolymers containing a three-carbon bridged ferrocene unit (I). However, the Mossbauer spectra obtained for polymers produced by cationic initiation do not show evidence for the three-membered bridge. Certainly PDVF(cationic) contains some acyclic unsaturated units, not necessarily pendant vinyl groups (II), but the low level of unsaturation suggests that cyclic units exist. Thus, for example, a five-carbon bridged bicyclic unit (VI) or a ladder structure (VII) may be found in these polymers, and would be consistent with the Mossbauer parameters obtained. Further polymerisation studies and Mossbauer and other spectroscopic studies of these polymers are in progress. 

Although the Mossbauer spectra of the sandwich compounds are insensitive to ring substitution, a wide range of parameters is observed for the mixed ferrocene-carbonyls. Values of quadrupole splitting span the range... 

Mossbauer studies of glassy nematic [4-6], cholesteric [7, 8] and smectic [9-12] liquid crystals allow the determination of characteristic Debye temperatures, order parameters, intramolecular and lattice contributions to the nuclear vibrational anisotropy, and molecular orientation [13] in the liquid crystal states. For example, Bekeshev et al. have shown from In/ versus temperature data at very low temperatures that MBBA [A -(/7-methoxybenzylidene)-/7-bu-tylaniline] and some liquid-crystalline di-substituted derivatives of ferrocene have weak intermolecular bonds that result in the appearance of additional degrees of free-... 

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