Magnetic Coupling and Optical Properties of the S 6 ‐Dodecakis(trifluoromethyl)fullerene Radical Anions in the Layered Salt (PPN + )[C 60 (CF 3 ) 12 .− ]

Poly(trifluoromethyl)fullerene S 6 ‐C 60 (CF 3 ) 12 was reduced by sodium fluorenone ketyl in the presence of (PPN)Cl (PPN=bis(triphenylphosphine)iminium) to afford the salt (PPN)[C 60 (CF 3 ) 12 ] ( 1 ), which contains C 60 (CF 3 ) 12 .− radical anions. In the crystal structure of 1 , C 60 (CF 3 ) 12 .− layers alternate with the PPN + cations. There are short F ⋅⋅⋅ F contacts between C 60 (CF 3 ) 12 .− radical anions within the layers but no C ⋅⋅⋅ C contacts. DFT calculations revealed that the negative charge on C 60 (CF 3 ) 12 .− 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 characteristic changes relative to those of neutral S 6 ‐C 60 (CF 3 ) 12 due to the formation of radical anions. The solid‐state electronic spectrum of 1 exhibits a single broad band at 738 nm attributed to C 60 (CF 3 ) 12 .− . Crystals of 1 show a narrow EPR signal with g =2.0025 (Δ H =0.45 mT) at 300 K. The temperature 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 / k B =−9.1 K. It was assumed that magnetic interaction between the C 60 (CF 3 ) 12 .− spins in the layers is mediated by short F ⋅⋅⋅ F contacts.