Effects of Environment on Intramolecular Electron Transfer in Mixed-valence 1′,1‴-Dinaphthylmethyl(biferrocenium) Triiodide: Structural and 57Fe Mössbauer Characteristics
✍ Scribed by Prof. Ten-Yuan Dong; Xiao-Qian Lai; Zhi-Wei Lin; Dr. Kuan-Jiuh Lin
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 423 KB
- Volume
- 36
- Category
- Article
- ISSN
- 0044-8249
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✦ Synopsis
Electron transfer in chemical''] and biological [2] systems has received considerable attention in the last few years. Recent studies of electron transfer in mixed-valence biferrocenium complexes 1-6 revealed that the environment surrounding a cation is perhaps the most important factor in determining the rate of intramolecular electron transfer.['" 31 Complexes 1-6 give unusual temperature-dependent Mossbauer spectra.[4] At temperatures below 77 K they each show two doublets, one for the Fe" and one for the Fe"' site (electron-transfer rate < lo7 s-I). In each case the two doublets move together upon increasing temperature and eventually become a single "average-valence'' doublet. Hendrickson et al. suggested that the temperature dependence of the Mossbauer spectrum is due to the onset of lattice dynamics associated with the triiodide counterions and alkyl s~bstituents.[~l At low temperatures (< 100 K) all parts of the crystal lattice of the complex are static.
As the temperature is increased, the thermal energy formed could be sufficient to trigger a cooperative phase transition in the crystal A crystallographic phase change was not observed in 1-6; we believe that the transition may be described in terms of a gradual (second-order) change with temperature.