A new class of solvent-free room temperature liquid fullerenes was synthesized by attaching a single substituent of 1,3,5-tris(alkyloxy)benzene unit to C-60 or C-70 under the Prato conditions. Although the C-60 monoadducts were single components after chromatographic purification, the C-70 monoadducts were isomeric mixtures due to the prolate spheroidal pi-chromophore. The alkyl chain length of the substituents significantly affected both melting points and rheological behavior of the fullerene derivatives. When the alkyl chains were short, the intermolecular pi-pi interactions of adjacent fullerene cores led to a melting point higher than room temperature. In contrast, in the case of exceedingly long alkyl chains, such as eicosyl (-C20H41) and docosanyl (-C22H45) groups, the van der Waals interactions among neighboring alkyl chains became dominant. Accordingly, only medium alkyl chain lengths could provide solvent-free fluidic fullerenes with low melting points. The rheological measurements of the liquid fullerenes at 25 degrees C revealed their unique liquid characteristics; molecular-level friction (or viscosity) and nanometer-scale clustering were noticed. It is generally thought that alkyl chains serve as a stabilizer of the fullerene core units. Thus, a longer chain or higher plasticity of the stabilizers would promote the disturbance of the core core interactions. It was indeed shown that longer alkyl chains resulted in a lower fluid viscosity. It was also found that metastable solid phases were produced by the noticeable van der Waals interaction between the long alkyl chains especially when a symmetric C-60 core was adopted. This interesting finding enabled the comparison of electrochemical activities of the C-60 unit between the solvent free liquid and metastable solid form, which revealed a superior electrochemical activity in the liquid state.