A combined experimental and theoretical study of the charge-transfer compound between C_(60)Br_8 and tetrathiafulvalene

摘要

C_(60)Br_8, unlike C_(60)Br_6 and C_(60)Cl_6, forms a solid charge-transfer compound with tetrathiafulvalene (TTF), the composition being C_(60)Br_8(TTF)_8. The unique complex-forming property of C_(60)Br_8 can be understood on the basis of the electronic structures of the halogenated derivatives of C_(60). Molecular orbital calculations show that the low LUMO energy of C_(60)Br_8 compared with the other halogen derivatives renders the formation of the complex with TTF favourable, the four virtual LUMOs being able to accept 8 electrons. The Raman spectrum of C_(60)Br_8(TTF)_8 shows a marked softening of the bands ( - 46 cm~(-1) on average) with respect to C_(60)Br_8, suggesting that indeed 8 electrons are transferred per C_(60)Br_8 molecule, one from each TTF molecule. The complex is weakly paramagnetic and shows a magnetic transition around 80 K.