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 =300-500nm and have a high triplet-state energy of 1.67eV. A cyanophenyl substituent renders BPTI such a strong electron acceptor (E-red=-0.11V vs. the normal hydrogen electrode) that electron-trapping reactions with O-2 and H2O do not occur. The BPTI radical anion on a fluorine-doped tin oxide|TiO2 electrode is persistent up to tens of seconds (t(1/2)=39s) in air-saturated buffer solution. As a result of favorable packing, theoretical electron mobilities (10(-2)approximate to 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.