Synthesis and properties of Bingel-type methanofullerene-pi-extended-TTF diads and triads.

Novel C(60)/pi-extended tetrathiafulvalene (exTTF) diads (12a-c) and triads [D(2)A (14a-c) and DA(2) (25, 27a-c)] have been synthesized by the Bingel cyclopropanation reaction of the respective exTTF-containing malonates and [60]fullerene. The reaction of exTTF-bismalonates with C(60) affords the respective C(60)-exTTF diads (26a-c) together with the triad C(60)-exTTF-C(60) (25, 27a-c) and a regioisomeric mixture of bisadducts (28b-c). Theoretical calculations (PM3) predict the favored geometry for triads 14a-c depending upon the orientation (up and down) of the 1,3-dithiole rings in the exTTFs, as well as the more stable regioisomers for the bisadducts 28. Cyclic voltammetry measurements reveal that C(60) and exTTF units do not intereact in the ground state. Compounds 26a-c and 27a-c are not electrochemically stable. A photoinduced electron transfer leading to the formation of the radical pair (C(60)(-)-exTTF(*+)) has been observed for compounds 14a-c.