Pronounced effects of grinding on rates of intramolecular electron transfer in mixed-valence 1′,2′,1‴,2‴-tetranaphthylmethyl- and 1′,3′,1‴,3‴-tetranaphthylmethyl-biferrocenium triiodides

The X-ray structural determinations of the neutral 1′,2′,1‴,2‴-tetranaphthylmethylbiferrocene and the mixed-valence 1′,3′,1‴,3‴-tetranaphthylmethylbiferrocenium triiodide have been determined. Our Mössbauer measurements for mixed-valence 1′,2′,1‴,2‴-tetranaphthylmethylbiferrocenium triiodide (1) and 1′,3′,1‴,3‴-tetranaphthylmethylbiferrocenium triiodide (2) indicate that the intramolecular electron-transfer rates in 1 and 2 are quite sensitive to the environmental perturbations caused by the grinding of sample. An interesting finding is that the Mössbauer results indicate that the unground diffusing sample of 1 is valence delocalized on the Mössbauer time scale above 180 K. However, the ground diffusing sample of 1 exhibits a Mössbauer spectrum characteristic of a valence-trapped cation which remains valence-trapped electronic state even at 300 K. The effects of grinding of samples are also observed in the EPR measurements.