Electron Transfer around a Molecular Corner

The distance dependence of electron transfer (ET) is commonly investigated in linear rigid rod‐like compounds, but studies of molecular wires with integrated corners imposing 90° angles are very rare. By using spirobifluorene as a key bridging element and by substituting it at different positions, two isomeric series of donor‐bridge‐acceptor compounds with either nearly linear or angled geometries were obtained. Photoinduced ET in both series is dominated by rapid through‐bond hole hopping across oligofluorene bridges over distances of up to 70 Å. Despite considerable conformational flexibility, direct through‐space and through‐solvent ET is negligible even in the angled series. The independence of the ET rate constant on the total number of fluorene units in the angled series is attributed to a rate‐limiting tunneling step through the spirobifluorene corner. This finding is relevant for multidimensional ET systems and grids in which individual molecular wires are interlinked at 90° angles.