First Solid-State Study of a Functionalized Fullerene Radical Anion Salt

First Solid-State Study of a Functionalized Fullerene Radical Anion Salt

Author: Sarah Millar

Compounds containing ionic fullerene moieties attract much attention owing to properties such as one-, two-, and three-dimensional metallic conductivity, superconductivity, and ferromagnetic ordering. This interest is also extended to fullerene derivatives in which addends are attached to the fullerene core. However, only a few compounds containing ionic fullerene derivatives have been obtained and characterized in the solid state.

Dmitri V. Konarev and colleagues, Institute of Problems of Chemical Physics, Chernogolovka, Russia, report the synthesis and isolation of the salt of the S6–C60(CF3)12⋅– radical anion with the bis(triphenylphosphine)iminium cation (PPN+) by reduction with sodium fluorenone ketyl. This is the first solid-state study on a radical anion of a highly functionalized fullerene derivative with twelve bulky addends.
According to X-ray crystallography, radical anions of C60(CF3)12⋅– in this salt are arranged in layers with short F⋅⋅⋅F contacts between C60(CF3)12⋅– moieties. Moreover, this salt shows strong magnetic coupling of spins in spite of shielding of the fullerene carbon cage by trifluoromethyl groups, a property that is likely due to partial localization of electron and spin density on fluorine atoms and mediation of the magnetic coupling through the network of short F⋅⋅⋅F contacts.

These results demonstrate that ionic compounds containing polyfunctionalized fullerenes can exhibit promising magnetic properties.

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