ESR‐Vis/NIR Spectroelectrochemical Study of C 70 (CF 3 ) 2 −. and C 70 (C 2 F 5 ) 2 −. Radical Anions

A spectroelectrochemical study of the two isostructural asymmetric perfluoroalkyl derivatives C 1 ‐7,24‐C 70 (CF 3 ) 2 and C 1 ‐7,24‐C 70 (C 2 F 5 ) 2 is presented. Reversible formation of their stable monoanion radicals is monitored by cyclic voltammetry and by in situ ESR‐Vis‐NIR spectroelectrochemistry. The ESR spectrum of the C 70 (CF 3 ) 2 −. radical is a 1:3:3:1 quartet with a 19 F hyperfine coupling constant (a(F)) of 0.323(4) G, demonstrating that the unpaired spin is coupled to only one of the two CF 3 groups. The 13 C satellites are assigned to specific carbon atoms. The ESR spectrum of the C 70 (C 2 F 5 ) 2 −. radical is an apparent octet with an apparent a(F) value of 0.83(2) G. DFT calculations suggest that this pattern is due to the superposition of spectra for four nearly isoenergetic C 70 (C 2 F 5 ) 2 −. conformers. Time‐dependent DFT calculations suggest that the NIR band at 1090 nm exhibited by both C 70 (R f ) 2 −. radical anions is assigned to the SOMO→LUMO+3 transition. The analogous NIR band exhibited by the closed‐shell C 70 (CF 3 ) 2 2− dianion was blue‐shifted to 1000 nm.