FeCl3-mediated synthesis of fullerenyl esters as low-LUMO acceptors for organic photovoltaic devices.

C(60) reacted with aromatic and aliphatic carboxylic acids in the presence of inexpensive FeCl(3) at room temperature to produce hydroxyfullerenyl esters C(60)(OCOR)(OH) in up to 68% isolated yield. The hydroxyl group was utilized in functional group transformations to obtain a diester derivative C(60)(OCOAr)(OCOPh) (Ar = 2,6-xylyl) and a siloxyl derivative C(60)(OCOAr)(OSiMe(3)). The diester and siloxyl derivatives were found to possess low-lying LUMO levels were utilized in organic photovoltaic devices showing 1.3% power conversion efficiency.