Oligothiophenes containing redox active groups

8 Oligothiophenes containing redox active groups Fullerene-functionalized oligothiophenes 

Due to the successful use of PCBM as acceptor material in solar cells, various attempts have been made to link Ceo covalently to an oligothiophene backbone in order to prepare D-A-based materials for photovoltaic devices by tuning their electronic properties [45, 46, 200, 201]. The attachment of fullerene units prevented large-scale phase separation in thin films and, despite the inclusion of bulky fullerene units, the soluble polymers retained their high order in thin films. However, the efficiency of such devices has been limited by competition between photoinduced electron transfer and energy transfer which occurs from the donor component to the fullerene. 

The first dyad molecule in which a fullerene was covalently linked to an oligothiophene 2.102 (Chart 1.20) was realized by Zotti elal. as a precursor for a corresponding polythiophene [202]. An azo 

Reagents and conditions (i) K2CO3, acetone, reflux 8 h (ii) N-methylglycene, Ceo, chlorobenzene, reflux. 

Terthiophene- fullerene dyad 2.106 (Chart 1.21), in which the fullerene unit was attached to the -position of the central thiophene unit through a rigid ethynyl spacer, was prepared by Komatsu et al. [207]. The synthesis was accomplished by lithiation of 3 -ethynylterthiophene [208] to generate the lithium acetylide, which subsequently was reacted with Ceo to form the ethynylated fullerenyl anion. By treatment of the latter with methyl iodide, dyad 2.106 was obtained in 35% yield. Another terthiophene-fullerene dyad 

---