Single Wall Carbon Nanotubes Filled with Metallocenes: a First Example of Non-Fullerene Peapods

Abstract

We report the synthesis and analysis of metallocenes (ferrocene, chromocene, ruthenocene, vanadocene, tungstenocene-dihydride) encapsulated in single wall carbon nanotubes (SWNTs). In the case of ferrocene, efficient filling of the SWNTs was accomplished from both the liquid and the vapor phase. The other two metallocenes were filled from the vapor phase. High resolution transmission electron microscopy reveals single molecular chains of metallocenes inside SWNTs. Molecules move under the electron beam in the SWNTs indicating the absence of strong chemical bonds between each other and the SWNT wall. Their movement freezes after short illumination as a result of irradiation damage. Energy dispersive X-ray spectrometry confirms the presence of iron, chromium, ruthenium, vanadium and tungsten.

Nano Sized Magnetic Particles with Diameters Less than 1 nm Encapsulated in Single-Walled Carbon Nanotubes

“…The contrast between the SWNT and the ferrocene clusters is notable, which evidently confirms that ferrocene molecules have successfully been filled in the SWNTs. This result is somewhat different from a previous description, 10,11) and in this case, almost no clear TEM images of metallocene in the SWNTs are observed due to the weak contrast and rapid moment of metallocene molecules during TEM observation. By comparison, in our case, the high filling yield may lead to high-density ferrocene clusters formed in the SWNT, which is considered to be responsible for the above difference.…”

Molecular Peapods as Supramolecular Carbon Allotropes

“…The filling with metallocenes occurred from the vapor phase with formation of collinear metallocene chains inside the nanotubes. Free molecular movement of the enclosed metallocenes indicates the absence of distinct interactions between the guest molecules and the SWCNT walls 34. Filling the peapods with larger molecules like a Zn‐diphenylporphyrin was successful, as established by absorption spectra and Raman measurements 35…”

“…Beside doping with fullerenes, SWCNTs can also be filled with molecules such as ferrocene, chromocene, ruthenocene, vanadocene and tungstenocene dihydride 34. The filling with metallocenes occurred from the vapor phase with formation of collinear metallocene chains inside the nanotubes.…”

Reactions over catalysts confined in carbon nanotubes

“…ferrocene and cobaltocene. [27][28][29] The process usually involves evacuation of the CNT channels followed by evaporation and decomposition of the metallocenes to form metals and carbon inside CNTs. However, a great deal of metal complexes also deposit on the CNT exterior surfaces, which need to be removed carefully.…”