Photoinduced electron transfer in a mesogenic donor-acceptor-donor system

A novel donor-acceptor-donor molecule consisting of two oligo(p-phenylene vinylene) (OPV4) units attached to a central perylene bisimide (PERY) core is described. This OPV4-PERY-OPV4 is the first mesogenic molecule that incorporates both p- and n-type semiconducting properties and possesses a liquid-crystalline mesophase, in which donor and acceptor functionalities self-assemble into an ordered material. Upon photoexcitation of the donor, a subpicosecond electron-transfer reaction occurs in OPV4-PERY-OPV4, both in solution and in (ordered) thin solid films. The lifetime of the charge-separated state is significantly longer in (ordered) thin films than in solution as a result of a reduction of geminate recombination by migration and spatial separation of charges in the film.