Magnetic Coupling and Optical Properties of the S6‐Dodecakis(trifluoromethyl)fullerene Radical Anions in the Layered Salt (PPN+)[C60(CF3)12.−]

Poly(trifluoromethyl)fullerene S6-C60(CF3)12 was re- duced by sodium fluorenone ketyl in the presence of (PPN)Cl (PPN = bis(triphenylphosphine)iminium) to afford the salt (PPN)(C60(CF3)12 )( 1), which contains C60(CF3)12 C radical anions. In the crystal structure of 1 ,C 60(CF3)12 C layers alter- nate with the PPN + cations. There are short F···F contacts between C60(CF3)12 C radical anions within the layers but no C···C contacts. DFT calculations revealed that the negative charge on C60(CF3)12 C is distributed mainly between sp 2 carbon and fluorine atoms, whereas spin density is localized mainly on the fullerene-cage sp 2 carbon atoms. IR and UV/ Vis/NIR spectra in the solid state and solution showed char- acteristic changes relative to those of neutral S6-C60(CF3)12 due to the formation of radical anions. The solid-state elec- tronic spectrum of 1 exhibits a single broad band at 738 nm attributed to C60(CF3)12 C. Crystals of 1 show a narrow EPR signal with g = 2.0025 (DH = 0.45 mT) at 300 K. The tempera- ture dependence of the integral intensity follows the Curie- Weiss law with a negative Weiss temperature of 11.8 K (30-300 K) indicating antiferromagnetic interaction of spins. This dependence was approximated by the Heisenberg model for one-dimensional chains of antiferromagnetically interacting spins with exchange interaction J/kB =9.1 K. It was assumed that magnetic interaction between the C60(CF3)12 C spins in the layers is mediated by short F···F con- tacts.