Interplay between barrier width and height in electron tunneling: Photoinduced electron transfer in porphyrin-based donor-bridge -acceptor systems

The electron transfer process in the ZnP-nB-AuP(super +) systems is verified by detection of formation and decay of the zinc porphyrin radical cation with femtosecond transient absorption spectroscopy. The efficiency of electron transfer, based on time-resolved fluorescence measurements, is 0.98, 0.77, 0.31, and 0.14 in C3H7CN for ZnP-nB-AuP(super +) with the edge to edge distance 12.7, 19.6, 26.5, an d33.4 Angstrom, respectively.