Unusual two-dimensional polymer network in Li4C60 — an ESR study.

At room temperature Li4C60 forms a unique two-dimensional polymer network where the bonding encounters [2+2] cycloaddition along one direction and a single C[Single_Bond]C bond along the perpendicular direction. This structure thus involves both so-far known bonding motifs and is unique among fullerene structures. The structural and electronic properties of this system were investigated by temperature dependent cw-ESR. The ESR signal of the polymer phase has an extremely narrow Lorentzian line with a linewidth of about 0.3 G. On heating, the transition from the low-temperature polymer phase to a metallic monomeric phase occurs above ∼250 °C. The high-temperature ESR signal has a characteristic Dysonian lineshape. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]