Reversible pressure - induced polymerization of Fe ( C

High pressure Raman, IR and X-ray diffraction (XRD) studies have been carried out on C 70 (Fe(C 5 H 5) 2) 2 (hereafter, " C 70 (Fc) 2 ") sheets. Theoretical calculation is further used to analyze the Electron Localization Function (ELF) and charge transfer in the crystal and thus to understand the transformation of C 70 (Fc) 2 under pressure. Our results show that even at room temperature dimeric phase and one dimensional (1D) polymer phase of C 70 molecules can be formed at about 3 and 8 GPa, respectively. The polymerization is found to be reversible upon decompression and the reversibility is related to the pressure-tuned charge transfer, as well as the overridden steric repulsion of counter ions. According to the layered structure of the intercalated ferrocene molecules formed in the crystal, we suggest that ferrocene acts as not only a spacer to restrict the polymerization of C 70 molecules within a layer, but also as charge reservoir to tune the polymerization process. This supplies a possible way for us to design the polymerization of fullerenes at suitable conditions.