Thermal release behavior of Fe+, CpFe+ and (Cp)2Fe+ ions from the molecular aggregate of β-cyclodextrin with ferrocene

The second-sphere interactions between ferrocene (Fc, guest) analogs and cyclodextrins (CD, host) have attracted sufficient attention in the past decades. However, there are some unanswered questions related with the interactions. For example, how such interactions are reflected by the thermal decomposition process? The present report describes our efforts to elucidate the correlation between the destruction of a second-sphere complex through the release of its members and the separate destruction of its members by a direct sample introduction device with programmed temperature in a gas chromatography coupled to time-of-flight mass spectrometry. Different kinds of mass spectra are analyzed to elicit accurate details about sample decomposition processes. It is found that on the one hand, the presence of Fc effectively delays the decomposition temperature of the complexed β-CD though a great part of Fc has been released from the complex. On the other hand, the special molecular structure of β-CD has served to prevent the sublimation of Fc to a certain degree. Furthermore, the thermal decomposition mode of the β-CD molecules complexed by Fc is drastically changed compared with that of free β-CD. Also, this study provides a paradigm that ferrocene decomposes in the β-CD cavity through the release of a CpFe+ moiety, and the remaining Cp ring remains contained in the host.