Highly Soluble Benzo[ghi]perylenetriimide Derivatives: Stable and Air-Insensitive Electron Acceptors for Artificial Photosynthesis

A series of new benzo[ghi]perylenetriimide (BPTI) derivatives has been synthesized and characterized. These remarkably soluble BPTI derivatives show strong optical absorption in the range of λ=300–500 nm and have a high triplet-state energy of 1.67 eV. A cyanophenyl substituent renders BPTI such a strong electron acceptor (E(red)=−0.11 V vs. the normal hydrogen electrode) that electron-trapping reactions with O(2) and H(2)O do not occur. The BPTI radical anion on a fluorine-doped tin oxide|TiO(2) electrode is persistent up to tens of seconds (t(1/2)=39 s) in air-saturated buffer solution. As a result of favorable packing, theoretical electron mobilities (10(−2)∼10(−1) cm(2) V(−1) s(−1)) are high and similar to the experimental values observed for perylene diimide and C(60) derivatives. Our studies show the potential of the cyanophenyl-modified BPTI compounds as electron acceptors in devices for artificial photosynthesis in water splitting that are also very promising nonfullerene electron-transport materials for organic solar cells.