A COMBINED EXPERIMENTAL AND THEORETICAL-STUDY OF THE CHARGE-TRANSFER COMPOUND BETWEEN C60BR8 AND TETRATHIAFULVALENE

C60Br8, unlike C60Br6 and C60Cl6, forms a solid charge-transfer compou nd with tetrathiafulvalene (TTF), the composition being C60Br8(TTF)(8) . The unique complex-forming property of C60Br8 can be understood on t he basis of the electronic structures of the halogenated derivatives o f C-60. Molecular orbital calculations show that the low LUMO energy o f C60Br8 compared with the other halogen derivatives renders the forma tion of the complex with TTF favourable, the four virtual LUMOs being able to accept 8 electrons. The Raman spectrum of C60Br8(TTF)(8) shows a marked softening of the bands (-46 cm(-1) on average) with respect to C60Br8 suggesting that indeed 8 electrons are transferred per C60Br 8 molecule, one from each TTF molecule. The complex is weakly paramagn etic and shows a magnetic transition around 80 K.