Photoinduced stepwise charge hopping in π-stacked perylene bisimide donor-bridge-acceptor arrays.

The mechanistic understanding of light-driven charge separation and charge-carrier transport within the frameworks of π-conjugated molecules is imperative to mimic natural photosynthesis and derive synthetic materials for solar energy conversion. In this regard, since the late 1980s, the distance and solvent dependence of stepwise (incoherent) charge-carrier hopping versus single-step (coherent) superexchange transport (tunnelling) have been studied in detail. Here we introduce structurally highly defined cofacially stacked donor-acceptor perylene bisimide arrays, which offer a high resemblance to natural systems. Similarity is achieved through controlling energy and electron transfer processes via intermolecular interactions between the π-stacked perylene bisimide subunits. Selective excitation of the donor induces electron transfer to the acceptor unit in polar solvents, facilitated by a 'through-stack' wire-like charge hopping mechanism with a low attenuation factor β = 0.21 Å, which suggests through-stack as being equally supportive for long-distance sequential electron transfer compared to the investigated 'through-bond' transfer along π-conjugated bridges.