Oxidation of Ferrocene in SiO₂ Gel and Solution

抄録

To obtain colored gels and glasses by the sol-gel method, we prepared SiO₂ gels doped with organometallic compounds, ferrocene and ferrocenium ion salt. After ferrocene was doped into a starting solution consisting of tetraethylorthosilicate and so on, the color of the sample (SiO₂ sol and gel) turned to blue from orange as the drying process proceeded from sol, via wet gel, to dried gel. We measured optical absorption and ESR spectra to investigate this color change. As a result, it is concluded that ferrocene molecule (orange) has been oxidized to ferrocenium ion (blue) in the sample. The oxidation of ferrocene in the sample is considered to be caused by H⁺, which has been produced in the hydrolysis and polycondensation processes. Moreover, ESR spectra of heat-treated samples reveal that the ferrocenium ion is gradually decomposed into iron oxide below 400 °C, and is fully decomposed at 900 °C.