Structurally Defined High-LUMO-Level 66π-[70]Fullerene Derivatives: Synthesis and Application in Organic Photovoltaic Cells

Abstract

Two new reactions for the synthesis of structurally defined 66π-electron [70]fullerene derivatives are reported. The first provides synthetic access to tetra-phenyl or [3 + 1] hybrid tetra-aryl C70 adducts via oxidation of a fullerene copper complex [Ar3C70–Cu–Ar′]− (Ar = Ph, 4-nBuC6H4; Ar′ = Ph, 4-MeOC6H4). The second provides access to alkyl fullerene ethers, C70Ar3(2-EH) via AgClO4-mediated coupling of a [70]fullerene bromide C70Ar3Br with 2-ethylhexanol (2-EH). The first reaction afforded two types of regioisomers including a 3,10,22,25-adduct (denoted type I) and a 7,10,22,25-adduct (type II). The haptotropic migration of the copper on a cuprio fullerene intermediate was suggested to be responsible for the generation of the two regioisomers. The second reaction gave only one regioisomer (type II). The eight new 66π-electron [70]fullerene derivatives synthesized are electrochemically and thermally stable, and their photoabsorption and electrochemical properties are closely related to the addition patt...