Light-induced electron transfer over distances of 5, 10, and 15 Å within water-filled yoctowells

A small series of variable-depth yoctowell cavities with 'functional' walls on aminated silica particles and gold electrodes has been established. The dimensions of the gaps formed were 2.2 nm in diameter with varying 'functional' depths of 5, 10, and 15 Å, depending on the length of bolaphiles applied and the position of the positive rim; these gaps were prepared through a Michael addition of the incorporated ene-amide groups. Using this construct and electrostatic interactions between the positive rim and anionic quinones as a means of immobilization, a porphyrin-quinone dyad system has been prepared. The distance between the donor and acceptor was changed systematically in aqueous solution, whilst maintaining a similar environment in each case. Upon photoexcitation of the porphyrin, efficient electron transfer occurs between the porphyrin and quinone units in a distance-dependent manner on the nanosecond timescale.