Abstract Image

The synthesis and characterization of different conjugated phthalocyanine–perylenemonoimidebenzimidazole [ZnPc-PBIm(OR)4] and nonconjugated phthalocyanine–perylenediimide [ZnPc-PDI(OR)4] dyads are carried out. UV–vis, 1H NMR, and electrochemistry measurements reveal the interaction between perylene and phthalocyanine moieties in the ground state in the conjugated hybrid and the lack of interaction in the nonconjugated one. Ultrafast transient absorption measurements show that a state with substantial charge-transfer character is formed in both compounds, but the rates for the formation and recombination from this state are much faster for the conjugated compound.

Quantum interference is a well-known phenomenon that dictates charge transport properties of single molecule junctions. However, reports on quantum interference in donor-bridge-acceptor molecules are scarce. This might be due to the difficulties in meeting the conditions for the presence of quantum interference in a donor-bridge-acceptor system. The electronic coupling between the donor, bridge, and acceptor moieties must be weak in order to ensure localised initial and final states for charge transfer. Yet, it must be strong enough to allow all bridge orbitals to mediate charge transfer. We present the computational route to the design of a donor-bridge-acceptor molecule that features the right balance between these contradicting requirements and exhibits pronounced interference effects.